Flash-spun sheet with improved balance of barrier and gas permeability

Abstract

The present invention relates to (i) a warm compression pre-bonded and thermally bonded sheet of nonwoven flash-spun plexifilamentary fibrils exhibiting a balance of permeability to gases and barrier properties to liquids and particles, and (ii) multilayer sheet structures and articles comprising at least one warm compression pre-bonded and thermally bonded sheet of nonwoven flash-spun plexifilamentary fibrils.

Description

[0001] TITLE

[0002] FLASH-SPUN SHEET WITH IMPROVED BALANCE OF BARRIER AND GAS PERMEABILITY

[0003] FIELD OF THE INVENTION

[0004] The present invention relates to (i) a warm compression pre-bonded and bonded sheet of nonwoven flash-spun plexifilamentary fibrils exhibiting a high permeability to gas and good barrier properties to liquids and particles, and (ii) multilayer sheet structures and articles comprising at least one warm compression pre-bonded and bonded sheet of nonwoven flash-spun plexifilamentary fibrils.

[0005] BACKGROUND

[0006] Flash-spun nonwoven materials have been developed with wide-ranging properties suitable for use in a variety of applications, including, but not limited to, (i) protective clothing, (ii) outdoor and sports apparel, and (iii) active packaging, in which an active substance is enclosed within a gas permeable selective barrier to form a protective package. The active package controls, reacts, or interacts with its contents or the environment in a container to optimize storage or transport conditions for articles also held within the container. Examples of active substances within active packaging are desiccants used for protection from humidity, oxygen absorbers to prevent oxidation, and ethylene scavengers for preservation of fruits and vegetables.

[0007] The production of such nonwoven materials usually involves two stages, a first stage in which fibrils are produced and laid down in an overlapping manner to produce a fibril assembly in the form of a sheet, and a second stage in which adjacent fibrils are bonded via thermal bonding to obtain a robust structure which cannot be easily disassembled. The properties of the final nonwoven sheet are impacted by various factors from the first and second stages.

[0008] Flash-spinning is a method for producing fibrils having a unique plexifilamentary structure. It involves preparing a solution of a fibril-forming polymer in a spin agent at a pressure above the vapor pressure of the spin agent and at a temperature above the normal boiling point of the spin agent, and releasing that solution into a zone of substantially lower temperature and pressure such that the spin agent flash evaporates and the polymer solidifies in the form of plexifilamentary fibrils. Examples of flash spinning processes are disclosed in US 3,081 ,519 and US 3,227,794.

[0009] The properties of flash-spun fibrils depend on, among other factors, the polymer or blend of polymers used to form them, the presence of functional fillers or additives in the spinfluid, the spin agent used to produce the spin fluid, the concentration of polymer in the spin fluid, and the temperature of the spin fluid during spinning. As with other types of spinning technology, the properties of an initial fibril assembly are modified by subsequent thermal bonding to produce a flash-spun nonwoven sheet.

[0010] Thermal bonding is a common process for bonding nonwoven sheets in which heat is used to soften and melt the polymer from which the fibrils are made, typically, by passing the nonwoven sheet through an arrangement of heated rolls. One or more back-up rolls, which form nips with the heated rolls to add pressure, may optionally be used. The degree of bonding can vary based on the temperature and pressure, and the time during which these are applied. Bonding of the nonwoven sheet also varies spatially depending on the rolls used and area to which the bonding is applied, e.g., using smooth surfaced rolls to apply uniform heat and pressure over the entire surface versus using patterned rolls to apply heat and pressure locally over only a portion of the surface to form an embossed pattern in the final nonwoven sheet.

[0011] US 3,442,740 and US 3,532,589 describe thermal bonding on a smooth heated roll where one or both sides of the nonwoven sheet are subjected to generally uniform, whole surface contact thermal bonding. In this process, a surface bonded nonwoven sheet product is obtained having a paper-like feel and a high stiffness. Thermal bonding using a thermal calender bonder, such as that described in US 5,972,147, also tends to produce a stiffer nonwoven sheet product. The smooth surface and relatively high stiffness of such whole surface bonded nonwoven sheet products makes them suitable for uses such as packaging, print media, and construction membranes. However, while a certain level of stiffness is required in breathable barriers used in active packaging, very high stiffness is a disadvantage as it makes folding and pleating to form a sachet more difficult, can cause seals to reopen on high speed filling machines, and prevents finished sachets from being able to conform their shape to the shape of their internal contents and the articles they are protecting. A moderate level of stiffness and flexibility is therefore desired in breathable barrier materials for active packaging.

[0012] US 5,972,147 describes a preheating step followed by a thermal bonding step, wherein a consolidated flash-spun sheet is passed through one or more preheating rolls, followed by one or more thermal calender nips. The preheating step is performed without added pressure, at a temperature within 15 °C of the peak melting temperature (Tm) of the sheet, so that the sheet is heated, without compression, at a temperature where melting may occur. A thermal bonding step follows the preheating step, where pressure is applied to the sheet with a nip at a pressure of at least 18 kg / linear cm and at a temperature sufficient to melt the fibers to form a bonded sheet.

[0013] US 4,247,318 describes a cold compression step prior to thermal bonding, which is performed using an unheated nip to apply compression. The nip is formed by two contactingrolls, the first roll having a hard metal surface and the second roll having a surface of at least 70 Shore D hardness. A multi-layer flash-spun sheet assembly is passed through an unheated nip under a pressure of 17-85 kg / cm (estimated pressure of 5-7 bar) applied over the width of the sheet to form a laminated sheet assembly. US 4,247,318 also describes the use of a preheating roll after the cold compression step and before the final bonding step. The preheating roll heats the sheet with no additional pressure above that created by the sheet tension and the wrap around the preheating roll.

[0014] Thermal bonding impacts different properties of the nonwoven sheet in different ways. The flux properties of nonwoven sheets, i.e., the ability of the fibril assembly to allow free movement of air or other gases such as water vapor through it, either by diffusion or by bulk flow under a pressure difference, may be altered in different ways depending on the bonding process. Heating can lead to relaxation of tension within the fibrils and fibril shrinkage and melting and fusion of adjacent fibrils, resulting in an increase in the space between the fibrils and an increase in flux. Conversely, pressure applied during bonding can compress the structure, reducing the space between the fibrils through which gases can move, resulting in a decrease in flux. Moreover, if temperatures and pressures are high enough to cause fibrils to melt and fuse together extensively, this can create film-like regions which allow very little flux.

[0015] The barrier properties of nonwoven sheets, i.e., the ability of the fibril assembly to prevent particles in the air from passing through it, or liquids such as water to penetrate it under pressure, tend to change in the converse manner to the flux properties after bonding. For instance, reduced pore sizes created by compression during bonding result in greater resistance to the passage of particles or liquids through the structure.

[0016] Mechanical properties such as delamination resistance, puncture and tear resistance, abrasion resistance, and tensile strength may increase or decrease as the degree of bonding increases. However, the stronger connections between fibrils resulting from bonding, and the limitation of their ability to move relative to each other, increases the stiffness of the bonded sheet.

[0017] These complex interactions of behaviors mean that thermally bonding a nonwoven sheet to produce a product for a particular application typically requires a compromise in the desired properties of the final sheet.

[0018] An ideal nonwoven sheet for use in protective clothing and outdoor and sports apparel should have high flux to allow rapid exhaust of warm air and water vapor from within the protective clothing and outdoor and sports apparel, and maintain a comfortable environment for the wearer, while having high barrier properties to solid and liquid particles to ensure the protection of the wearer.It is also preferable that the nonwoven sheet has low stiffness and a soft texture so that it does not provide noticeable resistance to the wearer’s movements.

[0019] An ideal nonwoven sheet for use in active packaging should have high water resistance, breathability, and particle barrier properties. An active package is a package which contains an active substance, usually in the form of granules or fine powders, commonly contained in a gas permeable bag or sachet that allows an exchange of gases between the interior of the sachet and the environment for the purpose of protecting an article. Where the article or environment may be wet or create high humidity levels, such as fruits and vegetables, the nonwoven sheet should have a high gas permeability, while also exhibiting low liquid permeability. The gas permeable bag or sachet must also provide a particle barrier to prevent the release of active substances outside of the package.

[0020] It is also preferable that, when used to make sachets or bags, the nonwoven sheet has a sufficiently high level of stiffness to allow fast and efficient forming of the sachets or bags and filling these in the production process, e.g., with active substances, and a sufficiently high level of flexibility or softness to allow folding and pleating. The finished sachet should be sufficiently soft and flexible such that its shape can conform to the shape of its interior contents and it can be inserted into a container with other articles without damaging them. It is further advantageous that the material has excellent tear, puncture, and abrasion resistance (high crock value) and does not release fibers into the environment inside the package (low linting).

[0021] While flash-spun sheets have demonstrated a good variety of desired properties, there has been a trade-off between the desired high gas permeability, low liquid permeability, and good protection properties. Therefore, there is a need for a flash-spun sheet for use in active packaging which provides an improved balance of permeability to gas and barrier properties to liquids and particles.

[0022] SUMMARY OF THE INVENTION

[0023] In one embodiment, the invention is directed to a thermally bonded sheet of nonwoven flash-spun plexifilamentary fibrils, the sheet having

[0024] (a) a basis weight from about 15 g / m2to about 120 g / m2,

[0025] (b) a Gurley Hill porosity of about 2 seconds or more,

[0026] (c) a hydrostatic head from about y cmH2O to about 3000 cmH2O, wherein y is (2 times the Gurley Hill porosity value) plus 180, and

[0027] (d) a particle penetration of about 7 % or less.

[0028] In a further embodiment, the invention is directed to a thermally bonded sheet of nonwoven flash-spun plexifilamentary fibrils, the sheet having

[0029] (a) a basis weight from about 15 g / m2to about 120 g / m2,(b) a Gurley Hill porosity of about 20 seconds or more,

[0030] (c) a hydrostatic head from p cmH2O to about 3000 cmH2O, wherein p is (2 times the Gurley Hill porosity value) plus 140, and

[0031] (d) a particle penetration of about 7 % or less.

[0032] In a further embodiment, the invention is directed to a thermally bonded sheet of nonwoven flash-spun plexifilamentary fibrils, the sheet having

[0033] (a) a basis weight from about 15 g / m2to about 48 g / m2,

[0034] (b) a Gurley Hill porosity of about 2 seconds to about 20 seconds,

[0035] (c) a hydrostatic head from m cmH2O to about 3000 cmH2O, wherein m is (2 times the Gurley Hill porosity value) plus 140, and

[0036] (d) a particle penetration of about 7 % or less.

[0037] In a further embodiment, the invention is directed to a thermally bonded sheet of nonwoven flash-spun plexifilamentary fibrils, the sheet having

[0038] (a) a basis weight from about 15 g / m2to about 48 g / m2,

[0039] (b) a hydrostatic head of 160 cmH2O or more,

[0040] (c) a particle penetration of about 5 % or less, and

[0041] (d) a water vapor transmission rate (WVTR) from about 20,000 g / m2 / day to about 100,000 g / m2 / day.

[0042] In a further embodiment, the invention is directed to a thermally bonded sheet of nonwoven flash-spun plexifilamentary fibrils, the sheet having

[0043] (a) a basis weight from about 15 g / m2to about 120 g / m2,

[0044] (b) a hydrostatic head of 220 cmH2O or more,

[0045] (c) a particle penetration of about 1 % or less, and

[0046] (d) a water vapor transmission rate (WVTR) from about 10,000 g / m2 / day to about 100,000 g / m2 / day.

[0047] In a further embodiment, the invention is directed to a thermally bonded sheet of nonwoven flash-spun plexifilamentary fibrils, the sheet having

[0048] (a) a basis weight from about 15 g / m2to about 54 g / m2,

[0049] (b) a Frazier porosity from about 0.3 m3 / m2 / min to about 3 m3 / m2 / min,

[0050] (c) a hydrostatic head from about 144 cmH2O to about 1000 cmH2O, and

[0051] (d) a particle penetration of about 1 % or less.In a still further embodiment, the invention is directed to a process for the preparation of a sheet of nonwoven flash-spun plexifilamentary fibrils which comprises the steps of:

[0052] (i) generating a spin fluid comprising

[0053] (a) from about 8 to about 20 weight percent of a polymer, based on the total amount of the spin fluid, and

[0054] (b) a spin agent comprising one or more hydrocarbons,

[0055] (ii) flash spinning the spin fluid at a temperature at or above about 190 °C and at a pressure that is above the vapor pressure of the spin fluid into a region of essentially atmospheric pressure to form plexifilamentary fibrils of the polymer, (Hi) collecting the plexifilamentary fibrils of the polymer on a collecting means as a sheet of nonwoven flash-spun plexifilamentary fibrils and applying pressure to the sheet to obtain a consolidated sheet,

[0056] (iv) pre-bonding the sheet by warm compression pre-bonding, and

[0057] (v) thermal bonding by whole surface contact bonding of the pre-bonded sheet.

[0058] In a still further embodiment, the invention is directed to a process for the preparation of a sheet of nonwoven flash-spun plexifilamentary fibrils which comprises the steps of:

[0059] (i) generating a spin fluid comprising

[0060] (a) from about 8 to about 11 weight percent of a polymer, and

[0061] (b) a spin agent comprising a chlorine-containing solvent, selected from dichloromethane, cis-1,2-dichloroethylene, trans- 1 ,2-dichloroethylene, ora mixture of cis-1 ,2-dichloroethylene and trans-1 ,2-dichloroethylene, in combination with a fluorine-containing solvent,

[0062] (ii) flash spinning the spin fluid at a temperature at or above about 190 °C and at a pressure that is above the vapor pressure of the spin fluid into a region of essentially atmospheric pressure to form plexifilamentary fibrils of the polymer, (iii) collecting the plexifilamentary fibrils of the polymer on a collecting means as a sheet of nonwoven flash-spun plexifilamentary fibrils and applying pressure to the sheet to obtain a consolidated sheet,

[0063] (iv) pre-bonding the sheet by warm compression pre-bonding, and

[0064] (v) thermal bonding by whole surface contact bonding of the pre-bonded sheet.

[0065] In a still further embodiment, the invention is directed to an article comprising a bonded sheet of flash-spun plexifilamentary fibrils of polyethylene, wherein the article has a basis weight from about 15 g / m2to about 54 g / m2, a Ret from about 2 m2Pa / Wto about 10 m2Pa / W, and a blood barrier measured according to ISO 16603 of at least 1.75 kPa, or a viral barrier measured according to ISO 16604 of at least 0 kPa, or both.DETAILED DESCRIPTION

[0066] Definitions of Terms and Test methods

[0067] Before addressing details of embodiments, some terms and test methods are defined or clarified. Unless otherwise mentioned, all tests were carried out without preconditioning of the samples. When average values are indicated herein, this refers to the arithmetic average.

[0068] Basis weight is determined according to ASTM D3776-09 using a sample size of 6 inch (15.24 cm) x6 inch (15.24 cm) and is reported in gram per square meter (g / m2). The reported value represents an average of at least 4 individual measurements.

[0069] Gurley Hill porosity (sometimes also referred to as “Gurley Porosity”) is a measure of the permeability of the sheet for gaseous materials. In particular, it is a measure of how long it takes a volume of gas to pass through an area of the sheet wherein a certain pressure gradient exists. Gurley-Hill porosity is determined in accordance with ISO 5636-5 (2003) using a Lorentzen & Wettre Model SE 166 or 516 from Lorentzen & Wettre, Kista, Sweden. The Gurley Hill porosity reported herein is expressed in seconds and represents an average of at least twelve individual measurements. The lower the Gurley Hill porosity, the greater the air permeability of the sheet.

[0070] Frazier porosity is a measure of the permeability of the sheet for gaseous materials. In particular, it measures the volume of gas which passes through a defined area of the sheet in a defined time, wherein a certain pressure gradient exists. Frazier porosity is determined in accordance with ASTM D737-18 (2023). The Frazier porosity reported herein is expressed in m3 / m2 / min (1 m3 / m2 / min corresponds to about 3.28 ft3 / ft2 / min). The reported values represent an average of at least 12 individual measurements. The higherthe Frazier porosity, the greater the air permeability of the sheet.

[0071] The hydrostatic head is a measure of the resistance of a sheet to penetration by liquid water under a static load. Herein the hydrostatic head is determined based on AATCC 127 (2003). The hydrostatic head is reported in cm of water column. Water in contact with one side of a 102.6 cm2section of a sample is pressurized at a rate of 60 + / - 3 cmH2O / min until three areas of the sample are penetrated by the water. The reported hydrostatic head is the average of at least 3 individual measurements. A higher hydrostatic head value refers to a sheet having a higher resistance to water penetration, that is, having a lower water permeability. For a laminated product, the surface of the sheet with the barrier function is the surface in contact with the water for measurement.

[0072] The water vapor transmission rate (WVTR) is measured according to ASTM D6701-16 using, e.g., a Mocon Permatran-W model. The reported WVTR is the average of at least 6 individual measurements.Particle penetration is a measure of the relative amount, expressed in percent, of particulates which pass through a material under given conditions. Herein particle penetration refers to the penetration of particles carried in air and is measured using a TSI 8130 instrument from TSI Incorporated, Shoreview, MN, United States, in accordance with US 42 CF 84 (2004), NIOSH Procedures No. RCT-APR-STP-57, 58, and 59. Airborne sodium chloride particles are generated having a particle size distribution with a count median diameter of 0.075 pm, a mass mean diameter of 0.3 pm, and a geometrical standard deviation of 1.8, with a volumetric air flow rate of 2.3 L / min. This volumetric air flow rate corresponds to a face velocity at the sample surface of 0.4 cm / s, which is representative of typical airflow conditions that the bonded sheet faces when used in a protective garment. In order to achieve a flow rate of 2.3 liter per minute, the control valve of the TSI 8130 is closed so that the air flow is that passing through the downstream photometer only. Measurements are performed with a rise time of 25 seconds and a measurement time of 4 seconds. The particle penetration in percent is determined based on the difference in light intensity measured by upstream and downstream photometers. The pressure drop over the sample is recorded in millimeters of water column (mmH20). The particle penetration values reported herein are averages of at least 3 measurements. Lower particle penetration values represent a higher particle barrier, whereas higher particle penetration values represent a lower particle barrier for the tested material.

[0073] Handle-O-Meter stiffness is a measure of the resistance of a sample to being pressed into a 10mm slot by a blade attached to a 1000g penetrator beam that is motor driven. It is measured by ASTM 6828-02 (2019)- Stiffness of Fabric by Blade / Slot Procedure and is expressed in gram-force (gf), convertible to N by multiplying gf by 9.8067 and dividing by 1000. In accordance with ASTM 6828 (2019), separate measurements are carried out in the machine direction (MD) and in the cross direction (XD) for the material being tested. The Handle-O-Meter stiffness reported herein is an average of at least 5 measurements in the machine direction (MD) and of at least 5 measurements in the cross direction (XD). A lower Handle-O-Meter stiffness value refers to a softer sheet or garment, i.e., a sheet or garment with a higher softness level has a lower handle-o-meter stiffness value. The Handle-O-Meter stiffness of a sample tends to increase proportionally with basis weight. Thus, the Handle-O-Meter stiffness can be normalized by dividing it by the basis weight.

[0074] The Ret (resistance to evaporative heat loss through the sample) is a measure of the breathability of a fabric, with lower values corresponding to higher breathability. The Ret is measured according to ISO 11092 (2014) except that the Ret is the average of 3 measurements on at least 1 specimen. The Ret is expressed in m2Pa / W. The Hohenstein Comfort Rating System indicates that breathable fabrics have Ret values between 13 and 30 m2Pa / W, very breathable fabrics have Ret values between 6 and 13 m2Pa / W, and extremely breathable fabrics have Ret values of below 6 m2Pa / W.The blood barrier is a measure of the resistance to penetration of a protective clothing material by blood and body fluids using synthetic blood as a body fluid simulant. The blood barrier is measured according to ISO 16603 (First Edition 2004-04-01), Procedure C, “Clothing for protection against contact with blood and body fluids — Determination of resistance of protective clothing materials to penetration by blood-borne pathogens — Test method using synthetic blood”. For each specimen, a “pass” or “fail” result is recorded for each pressure. The test specimen fails when the appearance of synthetic blood or other evidence of wetness is observed on the test surface of the specimen at the end of the specified pressure and time interval. If no liquid or characteristic discoloration appears for the duration of the test, then the specimen passes the test.

[0075] The viral barrier is a measure of the resistance to penetration of a protective clothing material by blood-borne pathogens. The viral barrier is measured according to ISO 16604 (First Edition 2004-04-01), Procedure C, “Clothing for protection against contact with blood and body fluids — Determination of resistance of protective clothing materials to penetration by blood-borne pathogens — Test method using Phi-X174 bacteriophage”. The torquing force to close the cell is 7 Nm instead of 13.6 Nm. For each specimen, a “pass” or “fail” result is recorded for each pressure. The test specimen passes when there is no detectable transfer (< 1 PFU / ml) of the Phi-X174 bacteriophage and there is no visual penetration on the viewing surface.

[0076] The resistance to chemical permeation is measured according to EN ISO 6529:2013, Method A "Protective clothing. Protection against chemicals. Determination of resistance of protective clothing materials to permeation by liquids and gases” using 18 wt% sulphuric acid, 30 wt% sulphuric acid, 10 wt% sodium hydroxide, or 40 wt% sodium hydroxide solutions as test liquids, without conditioning of the test specimen. A 112 mm diameter test specimen of the sheet or garment to be tested is clamped between two chambers of a test cell, each chamber having a volume of 100 cm3, such that the test specimen forms a barrier between the two chambers. One chamber, equipped with a conductivity meter, is filled with deionized water and is stirred constantly using a magnetic stirrer. At the start of the test, the other chamber is filled with the test liquid and the conductivity of the deionized water is then recorded every minute for up to 480 minutes. An increase in the conductivity of the deionized water indicates that test liquid has permeated through the test specimen, and the degree of increase in the conductivity can be correlated with a specific amount of permeate. The permeation breakthrough time at a normalized permeation rate of 1.0 pg / cm2 / min is the normalized breakthrough time (BTi.o). A test specimen of a sheet or garment suitable for use in manufacturing chemical protective apparel should have a resistance to chemical permeation of 60 minutes (1 hour) or above, 120 minutes (2 hours) or above, 240 minutes (4 hours) orabove, or 480 minutes (8 hours) or above, depending on the usage class of the chemical protective apparel.

[0077] Crock surface abrasion resistance is measured using a Crockmeter tester, Crockmaster Model 680 from PPT Group Corp, according to a modified method based on AATCC TM-8-2016e(2022)e, Procedure 10.1 Dry Crocking Test. Crockmeter testing is conducted under normal atmospheric conditions with unconditioned specimens. A piece of silicon carbide paper placed underneath the test specimen to prevent the test specimen from moving during the test. The test specimen is placed flat on the carbide paper and oriented such that the machine direction of the test specimen is parallel to the crockmeter finger path of rubbing, and taped on the left and right sides to the base of the Crockmeter with doublesided tape. A rubber disk, measuring %” diameter by 3 / 16” thickness is inserted in an aluminum holder with a total length of 1.7” (0.4” of the length is secured into the arm with a set screw) and a diameter of 1.0” with a weight of 1.76 ounces. The holder and rubber disk assembly is fastened to the crockmeter finger with the equipment set screw, so the rubber disk surface is in contact with the test specimen surface. The rubber disk is a Tabor CS-10 Weardisc® abradant (Part Number: 131434). The crank is turned so that the crockmeter finger traverses back and forth in a straight line across the surface of the sample (i.e., path of rubbing), at a rotation speed of 60 cycles per minute. One cycle represents a movement back and forth. The test is stopped at failure, and the number of cycles to that point is determined from the counter on the instrument. The flash-spun and bonded sheet being tested has a higher level of bonding on the outside surface of the sheet compared to the inside of the sheet. The failure is characterized by the number of strokes where the outside surface is disturbed and inside of the sheet is exposed. At this point, the area of disturbance is a local delamination where the surface tears and forms a flap having a dimension of greater than 5 mm in length as measured using a vernier caliper. The failures are registered only at the center portion of the swing bar stroke, not at the extreme ends where the finger reverses direction. If the surface does not fail in 50 cycles, the test is discontinued and a value of 50 is recorded as the number of cycles.

[0078] Melting point and melting extrapolated onset temperature are determined by differential scanning calorimetry, following the guidance provided in ASTM D3418 (Standard Test Method for Transition Temperatures and Enthalpies of Fusion and Crystallization of Polymers by Differential Scanning Calorimetry) and ASTM Standard F2625 (Standard Test Method for Measurement of Enthalpy of Fusion, Percent Crystallinity and Melting Point of Ultra-High-Molecular weight polyethylene by means of differential scanning calorimetry). For polyethylene, heating and cooling is performed under inert gas at a rate of 10 “C / minute, heating the sample first from room temperature to 210 °C, then cooling the sample back to room temperature and subsequently heating the sample a second time to 210 °C. The meltingpoint (Tm) reported herein is the peak temperature of the endotherm of the second heating cycle. The melting extrapolated onset temperature (Teim) reported herein is the temperature of the intersection of the onset slope of the melt endotherm and the baseline of the second heating cycle.

[0079] The melt flow rate is determined according to the method described in ISO 1133 (Plastics - Determination of the melt mass-flow rate (MFR) and the melt volume-flow rate (MVR) of thermoplastics). The melt flow rate for polyethylene is determined at a temperature of 190 °C and using a mass of 2160 grams (2.16 kg) or 21, 600 gram (21.6 kg). The melt flow rates of other polyolefins are performed at different temperatures as specified in ISO 1133.

[0080] Density is determined according to the method described in ISO 1183 (Plastics -Methods for determining the density of non-cellular plastics).

[0081] The term “polymer" is intended to embrace, without limitation, homopolymers, copolymers (such as for example, block, graft, random, and alternating copolymers), terpolymers, etc., and blends and modifications thereof. Furthermore, unless otherwise specifically limited, the term “polymer" shall include all possible geometrical configurations of the material. These configurations include, but are not limited to, isotactic, syndiotactic, and random symmetries.

[0082] The term “polyethylene” is intended to embrace not only homopolymers of ethylene, but also copolymers and terpolymers wherein at least 85 % of the recurring units are ethylene units, and the comonomer unit is, for example, propylene, butylene, hexene or octene. One useful polyethylene is a high-density polyethylene that has a melting point from about 125 °C to about 140 °C, a density of 0.94 to 0.98 grams per cubic centimeter, and a melt flow rate (ISO 1133 190 °C / 2160 grams) from 0.05 g / 10min to 30 g / 10min, preferably less than 4 g / 10min, and / or a melt flow rate (ISO 1133, 190 °C / 21 ,600 grams) from 1 g / 10min to 120 g / 10min or from 1 g / 10min to 50 g / 10min. The polyethylene may contain up to about 10 weight percent or up to about 5 weight percent of other polymers, such as other polyolefins, for example polypropylene.

[0083] The term “polymer type” refers to the chemical class into which the polymer falls, for example, polyethylene, polypropylene, etc.

[0084] The term “plexifilamentary” refers to a three-dimensional integral network or web of a multitude of thin, ribbon-like, fibrils of random length and a median fibril width of less than about 25 microns. In plexifilamentary structures, the fibrils are generally coextensively aligned with the longitudinal axis of the structure, and they intermittently unite and separate at irregular intervals in various places throughout the length, width, and thickness of the structure to form a continuous three-dimensional network or web.

[0085] The term “clothing” refers to a piece of garment to be worn. The term “protective clothing” is intended to refer to a single article of protective clothing, worn to provide protectionto the wearer’s skin against exposure to the environment, which covers or replaces personal clothing. The term “chemical protective clothing” is intended to refer to a single article of protective clothing, worn to provide protection to the wearer’s skin against exposure to or contact with chemicals, which covers or replaces personal clothing.

[0086] The terms “inside of the clothing”, “inside of the protective clothing”, and “inside of the chemical protective clothing” are intended to refer to the side of the clothing facing the wearer. The terms “outside of the clothing”, “outside of the protective clothing”, and “outside of the chemical protective clothing” are intended to refer to the opposite side of the clothing facing the environment.

[0087] The term “1,2-dichloroethylene” (1,2-DCE) is intended to embrace, without limitation, the cis-isomer, trans-isomer, or any combination or mixture of both isomers in any ratio.

[0088] The term “1H,2H-octafluorocyclopentane” is intended to embrace, without limitation, the cis-isomer, trans-isomer, or any combination or mixture of both isomers in any ratio.

[0089] The terms “spin agent” or “spin agent composition” refers to a composition comprising one or more solvents and any additives that are used to initially dissolve the polymer(s) to form the spin fluid. Suitable additives include stabilizers, such as antioxidants or acid scavengers.

[0090] The term “spin fluid” refers to a solution for spinning in a flash spinning process comprising a polymer and a spin agent. The solution may also include one or more additives.

[0091] Atmospheric pressure means 101.325 kPa. Essentially atmospheric pressure means 101.325 kPa ± 5 %.

[0092] As used herein, the singular forms "a," "an," and "the" include the plural, and reference to a particular numerical value includes at least that particular value, unless the context clearly dictates otherwise. When a range of values is expressed, another embodiment includes from the one particular value and / or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent "about," it will be understood that the particular value forms another embodiment. All ranges are inclusive and combinable.

[0093] Bonded Sheet of Nonwoven Flash-spun Plexifilamentary Fibrils

[0094] Provided herein is a thermally bonded sheet of nonwoven flash-spun plexifilamentary fibrils, the sheet having

[0095] (a) a basis weight from about 15 g / m2to about 120 g / m2,

[0096] (b) a Gurley Hill porosity of about 2 seconds or more,

[0097] (c) a hydrostatic head from about y cmH2O to about 3000 cmH2O, wherein y is (2 times the Gurley Hill porosity value) plus 180, and

[0098] (d) a particle penetration of about 7 % or less.Further provided herein is a thermally bonded sheet of nonwoven flash-spun plexifilamentary fibrils, the sheet having

[0099] (a) a basis weight from about 15 g / m2to about 120 g / m2,

[0100] (b) a Gurley Hill porosity of about 20 seconds or more,

[0101] (c) a hydrostatic head from p cmH2O to about 3000 cmH2O, wherein p is (2 times the Gurley Hill porosity value) plus 140, and

[0102] (d) a particle penetration of about 7 % or less.

[0103] Further provided herein is a thermally bonded sheet of nonwoven flash-spun plexifilamentary fibrils, the sheet having

[0104] (a) a basis weight from about 15 g / m2to about 48 g / m2,

[0105] (b) a Gurley Hill porosity of about 2 seconds to about 20 seconds,

[0106] (c) a hydrostatic head from m cmH2O to about 3000 cmH2O, wherein m is (2 times the Gurley Hill porosity value) plus 140, and

[0107] (d) a particle penetration of about 7 % or less.

[0108] Further provided herein is a thermally bonded sheet of nonwoven flash-spun plexifilamentary fibrils, the sheet having

[0109] (a) a basis weight from about 15 g / m2to about 48 g / m2,

[0110] (b) a hydrostatic head of 160 cmH2O or more,

[0111] (c) a particle penetration of about 5 % or less, and

[0112] (d) a water vapor transmission rate (WVTR) from about 20,000 g / m2 / day to about 100,000 g / m2 / day.

[0113] Further provided herein is a thermally bonded sheet of nonwoven flash-spun plexifilamentary fibrils, the sheet having

[0114] (a) a basis weight from about 15 g / m2to about 120 g / m2,

[0115] (b) a hydrostatic head of 220 cmH2O or more,

[0116] (c) a particle penetration of about 1 % or less, and

[0117] (d) a water vapor transmission rate (WVTR) from about 10,000 g / m2 / day to about 100,000 g / m2 / day.

[0118] Further provided herein is a thermally bonded sheet of nonwoven flash-spun plexifilamentary fibrils, the sheet having

[0119] (a) a basis weight from about 15 g / m2to about 54 g / m2,

[0120] (b) a Frazier porosity from about 0.3 m3 / m2 / min to about 3 m3 / m2 / min,

[0121] (c) a hydrostatic head from about 144 cmH2O to about 3000 cmH2O, and(d) a particle penetration of about 1 % or less.

[0122] The thermally bonded sheet described herein exhibits a desired combination of high gas permeability, low liquid permeability, and good protection properties.

[0123] In some embodiments, the bonded sheet has a basis weight from about 15 g / m2to about 120 g / m2, in other embodiments, the bonded sheet has a basis weight from about 15 g / m2to about 85 g / m2, in other embodiments, the bonded sheet has a basis weight from about 15 g / m2to about 75 g / m2, in other embodiments, the bonded sheet has a basis weight from about 15 g / m2to about 63 g / m2, in other embodiments, the bonded sheet has a basis weight from about 15 g / m2to about 54 g / m2, and in other embodiments, the bonded sheet has a basis weight from about 15 g / m2to about 48 g / m2. In some embodiments, the bonded sheet has a basis weight from about 30 g / m2to about 85 g / m2, and in other embodiments, the bonded sheet has a basis weight from about 48 g / m2to about 75 g / m2. In some embodiments, the bonded sheet has a basis weight from about 30 g / m2to about 63 g / m2, in other embodiments, the bonded sheet has a basis weight from about 30 g / m2to about 54 g / m2, and in other embodiments, the bonded sheet has a basis weight from about 30 g / m2to about 48 g / m2. In some embodiments, the bonded sheet has a basis weight from about 63 g / m2to about 120 g / m2, in other embodiments, the bonded sheet has a basis weight from about 63 g / m2to about 85 g / m2, and in other embodiments, the bonded sheet has a basis weight from about 63 g / m2to about 75 g / m2. In some embodiments, the bonded sheet has a basis weight from about 30 g / m2to about 54 g / m2, from about 33 g / m2to about 48 g / m2, from about 39 g / m2to about 48 g / m2, from about 39 g / m2to about 43 g / m2, from about 33 g / m2to about 37 g / m2, from about 34 g / m2to about 40 g / m2, from about 43 g / m2to about 48 g / m2, or from about 48 g / m2to about 54 g / m2.

[0124] In some embodiments, the bonded sheet has a Frazier porosity from about 0.3 m3 / m2 / min to about 3 m3 / m2 / min (about 1 ft3 / ft2 / min to about 10 ft3 / ft2 / min), in other embodiments, the bonded sheet has a Frazier porosity from about 0.3 m3 / m2 / min to about 1.5 m3 / m2 / min (about 1 ft3 / ft2 / min to about 5 ft3 / ft2 / min) .

[0125] In some embodiments, the bonded sheet has a Gurley Hill porosity of about 80 seconds or less, in other embodiments, the bonded sheet has a Gurley Hill porosity of about 40 seconds or less, in other embodiments, the bonded sheet has a Gurley Hill porosity of about 20 seconds or less, in other embodiments, the bonded sheet has a Gurley Hill porosity of about 15 seconds or less, in other embodiments, the bonded sheet has a Gurley Hill porosity of about 10 seconds or less, and in other embodiments, the bonded sheet has a Gurley Hill porosity of about 6 seconds or less. In some embodiments, the bonded sheet has a Gurley Hill porosity from about 2 seconds to about 80 seconds, in other embodiments, the bonded sheet has a Gurley Hill porosity from about 2 seconds to about 40 seconds, in otherembodiments, the bonded sheet has a Gurley Hill porosity from about 2 seconds to about 20 seconds, in other embodiments, the bonded sheet has a Gurley Hill porosity from about 2 seconds to about 15 seconds, in other embodiments, the bonded sheet has a Gurley Hill porosity from about 2 seconds to about 10 seconds, and in other embodiments, the bonded sheet has a Gurley Hill porosity from about 2 seconds to about 6 seconds. In some embodiments, the bonded sheet has a Gurley Hill porosity from about 6 seconds to about 20 seconds and in other embodiments, the bonded sheet has a Gurley Hill porosity from about 10 seconds to about 20 seconds. In some embodiments, the bonded sheet has a Gurley Hill porosity from about 20 seconds to about 80 seconds, in other embodiments, the bonded sheet has a Gurley Hill porosity from about 20 seconds to about 40 seconds.

[0126] In some embodiments, the bonded sheet has a particle penetration of about 7 % or less, in other embodiments, the bonded sheet has a particle penetration of about 5 % or less, in other embodiments, the bonded sheet has a particle penetration of about 3 % or less, in other embodiments, the bonded sheet has a particle penetration of about 1 % or less, and in other embodiments, the bonded sheet has a particle penetration of about 0.1 % or less. In some embodiments, the bonded sheet has a particle penetration from about 0.001 % to about 7 %, in other embodiments, the bonded sheet has a particle penetration from about 0.001 % to about 5 %, in other embodiments, the bonded sheet has a particle penetration from about 0.001 % to about 3 %, and in other embodiments, the bonded sheet has a particle penetration from about 0.001 % to about 1 %. In some embodiments, the bonded sheet has a particle penetration from about 0.01 % to about 7 %, in other embodiments, the bonded sheet has a particle penetration from about 0.01 % to about 5 %, in other embodiments, the bonded sheet has a particle penetration from about 0.01 % to about 3 %, and in other embodiments, the bonded sheet has a particle penetration from about 0.01 % to about 1 %. In some embodiments, the bonded sheet has a particle penetration from about 1 % to about 7 % and in other embodiments, the bonded sheet has a particle penetration from about 1 % to about 5 %.

[0127] In some embodiments, the bonded sheet has a hydrostatic head of about 3000 cmH2O or less, in other embodiments, the bonded sheet has a hydrostatic head of about 1000 cmH2O or less, in other embodiments, the bonded sheet has a hydrostatic head of about 800 cmH2O or less, in other embodiments, the bonded sheet has a hydrostatic head of about 600 CIT1H2O or less, and in other embodiments, the bonded sheet has a hydrostatic head of about 500 cmH2O or less. In some embodiments, the bonded sheet has a hydrostatic head from about 160 cmH2O to about 3000 cmH2O, in other embodiments, the bonded sheet has a hydrostatic head from about 180 cmH2O to about 3000 cmH2O, in other embodiments, the bonded sheet has a hydrostatic head from about 200 cmH2O to about 3000 cmH2O, in other embodiments, the bonded sheet has a hydrostatic head from about 220 cmH2O to about3000 cmH2O, in other embodiments, the bonded sheet has a hydrostatic head from about 240 cmH2O to about 3000 cmH2O, and in other embodiments, the bonded sheet has a hydrostatic head from about 300 cmH20 to about 3000 cmH2O. In some embodiments, the bonded sheet has a hydrostatic head from about 160 cmH2O to about 1000 cmH2O, in other embodiments, the bonded sheet has a hydrostatic head from about 180 cmH2O to about 1000 cmH2O, in other embodiments, the bonded sheet has a hydrostatic head from about 200 cmH2O to about 1000 cmH2O, in other embodiments, the bonded sheet has a hydrostatic head from about 220 cmH2O to about 1000 cmH2O, in other embodiments, the bonded sheet has a hydrostatic head from about 240 cmH2O to about 1000 cmH2O, and in other embodiments, the bonded sheet has a hydrostatic head from about 300 cmH2O to about 1000 cmH2O. In some embodiments, the bonded sheet has a hydrostatic head from about 160 cmH2O to about 800 cmH2O, in other embodiments, the bonded sheet has a hydrostatic head from about 180 cmH2O to about 800 cmH2O, in other embodiments, the bonded sheet has a hydrostatic head from about 200 cmH2O to about 800 cmH2O, in other embodiments, the bonded sheet has a hydrostatic head from about 220 cmH2O to about 800 cmH2O, in other embodiments, the bonded sheet has a hydrostatic head from about 240 cmH2O to about 800 cmH2O, and in other embodiments, the bonded sheet has a hydrostatic head from about 300 cmH2O to about 800 cmH2O. In some embodiments, the bonded sheet has a hydrostatic head from about 160 cmH2O to about 600 cmH2O, in other embodiments, the bonded sheet has a hydrostatic head from about 180 cmH2O to about 600 cmH2O, in other embodiments, the bonded sheet has a hydrostatic head from about 200 cmH2O to about 600 cmH2O, in other embodiments, the bonded sheet has a hydrostatic head from about 220 cmH2O to about 600 cmH2O, in other embodiments, the bonded sheet has a hydrostatic head from about 240 cmH2O to about 600 cmH2O, and in other embodiments, the bonded sheet has a hydrostatic head from about 300 cmH2O to about 600 cmH2O. In some embodiments, the bonded sheet has a hydrostatic head from about 160 cmH2O to about 500 cmH2O, in other embodiments, the bonded sheet has a hydrostatic head from about 180 cmH2O to about 500 cmH2O, in other embodiments, the bonded sheet has a hydrostatic head from about 200 cmH2O to about 500 cmH2O, in other embodiments, the bonded sheet has a hydrostatic head from about 220 cmH2O to about 500 cmH2O, in other embodiments, the bonded sheet has a hydrostatic head from about 240 cmH2O to about 500 cmH2O, and in other embodiments, the bonded sheet has a hydrostatic head from about 300 cmH2O to about 500 cmH2O.In some embodiments, the bonded sheet has a Gurley Hill porosity of about 2 seconds or more and a hydrostatic head from about y cmH2O to about 3000 cmH2O, wherein y is (2 times the Gurley Hill porosity value) plus z, with z being selected from 180, 195, and 205. Exemplarily, when the bonded sheet has a Gurley Hill porosity of 2 seconds, and z is 180, the bonded sheet has a hydrostatic head from about 184 cmH2O to about 3000 cmH2O, or when the bonded sheet has a Gurley Hill porosity of 10 seconds, and z is 195, the bonded sheet has a hydrostatic head from about 215 cmH2O to about 3000 cmH20.

[0128] In some embodiments, the bonded sheet has a hydrostatic head from about y cmH2O to about 3000 cmH2O, wherein y is (2 times the Gurley Hill porosity value) plus 180, in other embodiments, the bonded sheet has a hydrostatic head from about y cmH2O to about 3000 cmH2O, wherein y is (2 times the Gurley Hill porosity value) plus 195, and in other embodiments, the bonded sheet has a hydrostatic head from about y cmH2O to about 3000 cmH2O, wherein y is (2 times the Gurley Hill porosity value) plus 205.

[0129] In some embodiments, the bonded sheet has a hydrostatic head from about y cmH2O to about 1000 cmH2O, wherein y is (2 times the Gurley Hill porosity value) plus 180, in other embodiments, the bonded sheet has a hydrostatic head from about y cmH2O to about 1000 cmH2O, wherein y is (2 times the Gurley Hill porosity value) plus 195, and in other embodiments, the bonded sheet has a hydrostatic head from about y cmH2O to about 1000 cmH2O, wherein y is (2 times the Gurley Hill porosity value) plus 205.

[0130] In some embodiments, the bonded sheet has a hydrostatic head from about y cmH2O to about 600 cmH2O, wherein y is (2 times the Gurley Hill porosity value) plus 180, in other embodiments, the bonded sheet has a hydrostatic head from about y cmH2O to about 600 cmH2O, wherein y is (2 times the Gurley Hill porosity value) plus 195, and in other embodiments, the bonded sheet has a hydrostatic head from about y cmH2O to about 600 cmH2O, wherein y is (2 times the Gurley Hill porosity value) plus 205.

[0131] In some embodiments, the bonded sheet has a Gurley Hill porosity of about 20 seconds or more and a hydrostatic head from about p cmH2O to about 3000 cmH2O, wherein p is (2 times the Gurley Hill porosity value) plus q, with q being selected from 140, 155, 180, 195, and 205. Exemplarily, when the bonded sheet has a Gurley Hill porosity of 20 seconds, and q is 140, the bonded sheet has a hydrostatic head from about 180 cmH2O to about 3000 cmH2O, or when the bonded sheet has a Gurley Hill porosity of 25 seconds, and q is 155, the bonded sheet has a hydrostatic head from about 205 cmH2O to about 3000 cmH2O.

[0132] In some embodiments, the bonded sheet has a hydrostatic head from about p cmH2O to about 3000 cmH2O, wherein p is (2 times the Gurley Hill porosity value) plus 140, in other embodiments, the bonded sheet has a hydrostatic head from about p cmH2O to about 3000 cmH2O, wherein p is (2 times the Gurley Hill porosity value) plus 155, in other embodiments, the bonded sheet has a hydrostatic head from about p cmH2O to about 3000 cmH2O, whereinp is (2 times the Gurley Hill porosity value) plus 180, in other embodiments, the bonded sheet has a hydrostatic head from about p cmH20 to about 3000 cmH20, wherein p is (2 times the Gurley Hill porosity value) plus 195, and in other embodiments, the bonded sheet has a hydrostatic head from about p cmH2O to about 3000 cmH2O, wherein p is (2 times the Gurley Hill porosity value) plus 205.

[0133] In some embodiments, the bonded sheet has a hydrostatic head from about p cmH2O to about 1000 cmH2O, wherein p is (2 times the Gurley Hill porosity value) plus 140, in other embodiments, the bonded sheet has a hydrostatic head from about p cmH2O to about 1000 cmH2O, wherein p is (2 times the Gurley Hill porosity value) plus 155, in other embodiments, the bonded sheet has a hydrostatic head from about p cmH2O to about 1000 cmH2O, wherein p is (2 times the Gurley Hill porosity value) plus 180, in other embodiments, the bonded sheet has a hydrostatic head from about p cmH2O to about 1000 cmH2O, wherein p is (2 times the Gurley Hill porosity value) plus 195, and in other embodiments, the bonded sheet has a hydrostatic head from about p cmH2O to about 1000 cmH2O, wherein p is (2 times the Gurley Hill porosity value) plus 205.

[0134] In some embodiments, the bonded sheet has a hydrostatic head from about p cmH2O to about 600 cmH2O, wherein p is (2 times the Gurley Hill porosity value) plus 140, in other embodiments, the bonded sheet has a hydrostatic head from about p cmH2O to about 600 cmH2O, wherein p is (2 times the Gurley Hill porosity value) plus 155, in other embodiments, the bonded sheet has a hydrostatic head from about p cmH2O to about 600 cmH2O, wherein p is (2 times the Gurley Hill porosity value) plus 180, in other embodiments, the bonded sheet has a hydrostatic head from about p cmH2O to about 600 cmH2O, wherein p is (2 times the Gurley Hill porosity value) plus 195, and in other embodiments, the bonded sheet has a hydrostatic head from about p cmH20 to about 600 cmH2O, wherein p is (2 times the Gurley Hill porosity value) plus 205.

[0135] In some embodiments, the bonded sheet has a Gurley Hill porosity of about 2 seconds to about 20 seconds and a hydrostatic head from about m cmH20 to about 3000 cmH2O, wherein m is (2 times the Gurley Hill porosity value) plus n, with n being selected from 140, 155, 180, 195, and 205. Exemplarily, when the bonded sheet has a Gurley Hill porosity of 2 seconds, and n is 140, the bonded sheet has a hydrostatic head from about 144 cmH2O to about 3000 cmH2O, or when the bonded sheet has a Gurley Hill porosity of 20 seconds, and n is 155, the bonded sheet has a hydrostatic head from about 195 cmH2O to about 3000 cmH2O.

[0136] In some embodiments, the bonded sheet has a hydrostatic head from about m cmH2O to about 3000 cmH2O, wherein m is (2 times the Gurley Hill porosity value) plus 140, in other embodiments, the bonded sheet has a hydrostatic head from about m cmH2O to about 3000 cmH2O, wherein m is (2 times the Gurley Hill porosity value) plus 155, in other embodiments,the bonded sheet has a hydrostatic head from about m cmH2O to about 3000 cmH2O, wherein m is (2 times the Gurley Hill porosity value) plus 180, in other embodiments, the bonded sheet has a hydrostatic head from about m cmH2O to about 3000 cmH2O, wherein m is (2 times the Gurley Hill porosity value) plus 195, and in other embodiments, the bonded sheet has a hydrostatic head from about m cmH2O to about 3000 cmH2O, wherein m is (2 times the Gurley Hill porosity value) plus 205.

[0137] In some embodiments, the bonded sheet has a hydrostatic head from about m cmH2O to about 1000 cmH2O, wherein m is (2 times the Gurley Hill porosity value) plus 140, in other embodiments, the bonded sheet has a hydrostatic head from about m cmH2O to about 1000 cmH2O, wherein m is (2 times the Gurley Hill porosity value) plus 155, in other embodiments, the bonded sheet has a hydrostatic head from about m cmH2O to about 1000 cmH2O, wherein m is (2 times the Gurley Hill porosity value) plus 180, in other embodiments, the bonded sheet has a hydrostatic head from about m cmH2O to about 1000 cmH2O, wherein m is (2 times the Gurley Hill porosity value) plus 195, and in other embodiments, the bonded sheet has a hydrostatic head from about m cmH2O to about 1000 cmH2O, wherein m is (2 times the Gurley Hill porosity value) plus 205.

[0138] In some embodiments, the bonded sheet has a hydrostatic head from about m cmH2O to about 600 cmH2O, wherein m is (2 times the Gurley Hill porosity value) plus 140, in other embodiments, the bonded sheet has a hydrostatic head from about m cmH2O to about 600 cmH2O, wherein m is (2 times the Gurley Hill porosity value) plus 155, in other embodiments, the bonded sheet has a hydrostatic head from about m cmH2O to about 600 cmH2O, wherein m is (2 times the Gurley Hill porosity value) plus 180, in other embodiments, the bonded sheet has a hydrostatic head from about m cmH2O to about 600 cmH2O, wherein m is (2 times the Gurley Hill porosity value) plus 195, and in other embodiments, the bonded sheet has a hydrostatic head from about m cmH2O to about 600 cmH20, wherein m is (2 times the Gurley Hill porosity value) plus 205.

[0139] In some embodiments, the bonded sheet has a WVTR from about 10,000 g / m2 / day to about 100,000 g / m2 / day, in other embodiments, the bonded sheet has a WVTR from about 10,000 g / m2 / day to about 80,000 g / m2 / day, in other embodiments, the bonded sheet has a WVTR from about 10,000 g / m2 / day to about 60,000 g / m2 / day, and in other embodiments, the bonded sheet has a WVTR from about 10,000 g / m2 / day to about 40,000 g / m2 / day. In some embodiments, the bonded sheet has a WVTR from about 20,000 g / m2 / day to about 100,000 g / m2 / day, in other embodiments, the bonded sheet has a WVTR from about 20,000 g / m2 / day to about 80,000 g / m2 / day, and in other embodiments, the bonded sheet has a WVTR from about 20,000 g / m2 / day to about 60,000 g / m2 / day. In some embodiments, the bonded sheet has a WVTR from about 30,000 g / m2 / day to about 100,000 g / m2 / day, in other embodiments, the bonded sheet has a WVTR from about 30,000 g / m2 / day to about 80,000 g / m2 / day, and inother embodiments, the bonded sheet has a WVTR from about 30,000 g / m2 / day to about 60,000 g / m2 / day. In some embodiments, the bonded sheet has a WVTR from about 40,000 g / m2 / day to about 100,000 g / m2 / day, in other embodiments, the bonded sheet has a WVTR from about 40,000 g / m2 / day to about 80,000 g / m2 / day, and in other embodiments, the bonded sheet has a WVTR from about 40,000 g / m2 / day to about 60,000 g / m2 / day.

[0140] In some embodiments, the bonded sheet has a Handle-O-Meter stiffness from about 300 mN to about 2000 mN, in other embodiments, the bonded sheet has a Handle-O-Meter stiffness from about 300 mN to about 1300 mN, in other embodiments, the bonded sheet has a Handle-O-Meter stiffness from about 300 mN to about 1000 mN, and in other embodiments, the bonded sheet has a Handle-O-Meter stiffness from about 300 mN to about 800 mN. In some embodiments, the bonded sheet has a Handle-O-Meter stiffness from about 2000 mN to about 8000 mN and in other embodiments, the bonded sheet has a Handle-O-Meter stiffness from about 2000 mN to about 4000 mN. In some embodiments, the bonded sheet has a Handle-O-Meter stiffness from about 4000 mN to about 8000 mN.

[0141] In some embodiments, the bonded sheet has a Handle-O-Meter stiffness, normalized to basis weight, of about 4 mN / (g / m2) to about 30 mN / (g / m2), in other embodiments, the bonded sheet has a Handle-O-Meter stiffness, normalized to basis weight, of about 4 mN / (g / m2) to about 25 mN / (g / m2), and in other embodiments, the bonded sheet has a Handle-O-Meter stiffness, normalized to basis weight, of about 4 mN / (g / m2) to about 20 mN / (g / m2). In some embodiments, the bonded sheet has a Handle-O-Meter stiffness, normalized to basis weight, of about 30 mN / (g / m2) to about 70 mN / (g / m2), in other embodiments, the bonded sheet has a Handle-O-Meter stiffness, normalized to basis weight, of about 30 mN / (g / m2) to about 60 mN / (g / m2), and in other embodiments, the bonded sheet has a Handle-O-Meter stiffness, normalized to basis weight, of about 30 mN / (g / m2) to about 50 mN / (g / m2). In some embodiments, the bonded sheet has a Handle-O-Meter stiffness, normalized to basis weight, of about 1 mN / (g / m2) to about 30 mN / (g / m2), of about 1 mN / (g / m2) to about 20 mN / (g / m2), of about 2 mN / (g / m2) to about 10 mN / (g / m2), of about 2 mN / (g / m2) to about 5 mN / (g / m2), or of about 10 mN / (g / m2) to about 30 mN / (g / m2).

[0142] In some embodiments, the bonded sheet has a crock surface abrasion resistance from 10 to 50 cycles, in other embodiments, the bonded sheet has a crock surface abrasion resistance from 20 to 50 cycles, or from 30 to 50 cycles, or from 40 to 50 cycles.

[0143] In some embodiments, the bonded sheet has a Ret from about 2 m2Pa / W to about 10 m2Pa / W, from about 2 m2Pa / W to about 8 m2Pa / W, or from about 2 m2Pa / W to about 6 m2Pa / W. In other embodiments, the bonded sheet has a Ret from about 2 m2Pa / W to about 4 m2Pa / W, from about 4 m2Pa / W to about 6 m2Pa / W, or from about 3 m2Pa / W to about 5 m2Pa / W.In some embodiments, the bonded sheet has a blood barrier measured according to ISO 16603 of at least 1.75 kPa, of at least 3.5 kPa of at least 7 kPa, of at least 14 kPa, or of at least 20 kPa.

[0144] In some embodiments, the bonded sheet has a viral barrier measured according to ISO 16604 of at least 0 kPa, of at least 1.75 kPa, of at least 3.5 kPa, of at least 7 kPa, of at least 14 kPa, or of at least 20 kPa.

[0145] In some embodiments, the bonded sheet has a blood barrier measured according to ISO 16603 of at least 1.75 kPa and a viral barrier measured according to ISO 16604 of at least 0 kPa. In other embodiments, the bonded sheet has a blood barrier measured according to ISO 16603 of at least 3.5 kPa and a viral barrier measured according to ISO 16604 of at least 1.75 kPa or at least 3.5 kPa. In other embodiments, the bonded sheet has a blood barrier measured according to ISO 16603 of at least 7 kPa and a viral barrier measured according to ISO 16604 of at least 1.75 kPa, at least 3.5 kPa, or at least 7 kPa. In other embodiments, the bonded sheet has a blood barrier measured according to ISO 16603 of at least 14 kPa and a viral barrier measured according to ISO 16604 of at least 3.5 kPa, at least 7 kPa, or at least 14 kPa. In other embodiments, the bonded sheet has a blood barrier measured according to ISO 16603 of at least 20 kPa and a viral barrier measured according to ISO 16604 of at least 7 kPa, at least 14 kPa, or at least 14 kPa.

[0146] In some embodiments, the bonded sheet has a resistance to chemical permeation, BT-i.o, measured according to ISO 6529 against 10 wt% NaOH or 40 wt% NaOH of 60 min or above, of 120 min or above, of 240 min or above, or of 480 min or above. In other embodiments, the sheet has a resistance to chemical permeation, BT-i.o, measured according to ISO 6529 against 18 wt% H2SO4or 30 wt% H2SO4of 60 min or above, of 120 min or above, of 240 min or above, or of 480 min or above.

[0147] In some embodiments, the bonded sheet has a resistance to chemical permeation, BT-i.o, measured according to ISO 6529 against 10 wt% NaOH or 40 wt% NaOH and against 18 wt% H2SO4or 30 wt% H2SO4of 60 min or above, of 120 min or above, of 240 min or above, or of 480 min or above.

[0148] In some embodiments, the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene. In some embodiments, the polyethylene is high-density polyethylene (HDPE), or blends / mixtures of high-density polyethylene (HDPE) with low-density polyethylene (LDPE), in particular blends / mixtures of high-density polyethylene (HDPE) with linear low-density polyethylene (LLDPE).

[0149] In some embodiments, the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 15 g / m2to about 54 g / m2, a Frazier porosity from about 0.3 m3 / m2 / min to about 3 m3 / m2 / min, a hydrostatic headfrom about 144 cmH2O to about 1000 cmH2O or from about 159 cmH2O to about 1000 cmH2O, and a particle penetration of about 1 % or less.

[0150] In some embodiments, the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 15 g / m2to about 54 g / m2, a Frazier porosity from about 0.3 m3 / m2 / min to about 3 m3 / m2 / min, a hydrostatic head from about 144 cmH2O to about 1000 cmH2O or from about 159 cmH2O to about 1000 cmH2O, a particle penetration of about 1 % or less, a Ret from about 2 m2Pa / W to about 10 m2Pa / W, and a blood barrier measured according to ISO 16603 of at least 1.75 kPa, or a viral barrier measured according to ISO 16604 of at least 0 kPa, or both, and optionally a resistance to chemical permeation, BTi.o, measured according to ISO 6529 against 10 wt% NaOH of 120 min or above, or of 240 min or above, and a resistance to chemical permeation, BT1 0, measured according to ISO 6529 against 18 wt% H2SO4of 120 min or above, or of 240 min or above.

[0151] In some embodiments, the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 30 g / m2to about 54 g / m2, a Frazier porosity from about 0.3 m3 / m2 / min to about 3 m3 / m2 / min, a hydrostatic head from about 179 cmH2O to about 1000 cmH2O, and a particle penetration of about 1 % or less.

[0152] In some embodiments, the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 15 g / m2to about 54 g / m2, a Frazier porosity from about 0.3 m3 / m2 / min to about 3 m3 / m2 / min, a hydrostatic head from about 144 cmH2O to about 1000 cmH2O, a particle penetration of about 1 % or less, and a Handle-O-Meter stiffness, normalized to basis weight, of about 4 mN / (g / m2) to about 30 mN / (g / m2).

[0153] In some embodiments, the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 15 g / m2to about 54 g / m2, a Frazier porosity from about 0.3 m3 / m2 / min to about 3 m3 / m2 / min, a hydrostatic head from about 159 cmH2O to about 1000 cmH2O, and a particle penetration of about 1 % or less.

[0154] In some embodiments, the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 15 g / m2to about 54 g / m2, a Frazier porosity from about 0.3 m3 / m2 / min to about 3 m3 / m2 / min, a hydrostatic head from about 159 cmH2O to about 1000 cmH2O, a particle penetration of about 1 % or less, and a Handle-O-Meter stiffness, normalized to basis weight, of about 4 mN / (g / m2) to about 30 mN / (g / m2).

[0155] In some embodiments, the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 15 g / m2to about 54 g / m2, a Frazier porosity from about 0.3 m3 / m2 / min to about 3 m3 / m2 / min, a hydrostatic head from about 144 cmH2O to about 1000 cmH2O, a particle penetration of about 1 % or less, anda water vapor transmission rate (WVTR) from about 20,000 g / m2 / day to about 100,000 g / m2 / day.

[0156] In some embodiments, the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 15 g / m2to about 120 g / m2, a Gurley Hill porosity of about 2 seconds or more, a hydrostatic head from about y cmH2O to about 3000 CIT1H2O, wherein y is (2 times the Gurley Hill porosity value) plus 180, and a particle penetration of about 7 % or less, or of about 3 % or less, or of about 1 % or less.

[0157] In some embodiments, the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 15 g / m2to about 120 g / m2, a Gurley Hill porosity of about 2 seconds or more, a hydrostatic head from about y cmH2O to about 3000 cmH2O, wherein y is (2 times the Gurley Hill porosity value) plus 180, a particle penetration of about 7 % or less, of about 3 % or less, or of about 1 % or less, a Ret from about 2 m2Pa / W to about 10 m2Pa / W, and a blood barrier measured according to ISO 16603 of at least 1.75 kPa, or a viral barrier measured according to ISO 16604 of at least 0 kPa, or both, and optionally a resistance to chemical permeation, BT-1,0, measured according to ISO 6529 against 10 wt% NaOH of 120 min or above, or of 240 min or above, and a resistance to chemical permeation, BT1 0, measured according to ISO 6529 against 18 wt% H2SO4of 120 min or above, or of 240 min or above.

[0158] In some embodiments, the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 15 g / m2to about 120 g / m2, a Gurley Hill porosity of about 2 seconds or more, a hydrostatic head from about y cmH2O to about 3000 cmH2O, wherein y is (2 times the Gurley Hill porosity value) plus 195, and a particle penetration of about 1 % or less.

[0159] In some embodiments, the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 15 g / m2to about 54 g / m2, a Gurley Hill porosity of about 2 seconds or more, a hydrostatic head from about y cmH2O to about 3000 cmH2O, wherein y is (2 times the Gurley Hill porosity value) plus 180, and a particle penetration of about 7 % or less, or of about 3 % or less, or of about 1 % or less.

[0160] In some embodiments, the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 30 g / m2to about 54 g / m2, a Gurley Hill porosity of about 2 seconds or more, a hydrostatic head from about y cmH2O to about 3000 cmH2O, wherein y is (2 times the Gurley Hill porosity value) plus 180, and a particle penetration of about 7 % or less, or of about 3 % or less, or of about 1 % or less.

[0161] In some embodiments, the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 15 g / m2to about 63 g / m2, a Gurley Hill porosity of about 2 seconds or more, a hydrostatic head from about ycmH2O to about 3000 cmH20, wherein y is (2 times the Gurley Hill porosity value) plus 180, and a particle penetration of about 7 % or less, or about 3 % or less, or about 1 % or less.

[0162] In some embodiments, the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 30 g / m2to about 63 g / m2, a Gurley Hill porosity of about 2 seconds or more, a hydrostatic head from about y cmH2O to about 3000 cmH2O, wherein y is (2 times the Gurley Hill porosity value) plus 180, and a particle penetration of about 7 % or less, or about 3 % or less, or about 1 % or less.

[0163] In some embodiments, the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 15 g / m2to about 63 g / m2, a Gurley Hill porosity of about 2 seconds or more, a hydrostatic head from about y cmH2O to about 3000 cmH2O, wherein y is (2 times the Gurley Hill porosity value) plus 195, and a particle penetration of about 3 % or less or about 1 % or less.

[0164] In some embodiments, the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 15 g / m2to about 63 g / m2, a Gurley Hill porosity of about 2 seconds or more, a hydrostatic head from about y cmH2O to about 3000 cmH2O, wherein y is (2 times the Gurley Hill porosity value) plus 180, a particle penetration of about 3 % or less or about 1 % or less, and a Handle-O-Meter stiffness, normalized to basis weight, of about 4 mN / (g / m2) to about 30 mN / (g / m2).

[0165] In some embodiments, the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 15 g / m2to about 63 g / m2, a Gurley Hill porosity of about 2 seconds or more, a hydrostatic head from about y cmH2O to about 3000 cmH2O, wherein y is (2 times the Gurley Hill porosity value) plus 180, a particle penetration of about 3 % or less or about 1 % or less, and a water vapor transmission rate (WVTR) from about 10,000 g / m2 / day to about 100,000 g / m2 / day.

[0166] In some embodiments, the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 15 g / m2to about 63 g / m2, a Gurley Hill porosity of about 2 seconds or more, a hydrostatic head from about y cmH2O to about 3000 cmH2O, wherein y is (2 times the Gurley Hill porosity value) plus 180, a particle penetration of about 3 % or less or about 1 % or less, a Handle-O-Meter stiffness, normalized to basis weight, of about 4 mN / (g / m2) to about 30 mN / (g / m2), and a water vapor transmission rate (WVTR) from about 10,000 g / m2 / day to about 100,000 g / m2 / day.

[0167] In some embodiments, the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 30 g / m2to about 63 g / m2or from about 30 g / m2to about 54 g / m2, a Gurley Hill porosity of about 2 seconds or more, a hydrostatic head from about y cmH2O to about 3000 cmH2O, wherein y is (2 times the Gurley Hill porosity value) plus 180, and a particle penetration of about 1 % or less.In some embodiments, the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 63 g / m2to about 120 g / m2, a Gurley Hill porosity of about 2 seconds or more, a hydrostatic head from about y cmH2O to about 3000 cmH2O, wherein y is (2 times the Gurley Hill porosity value) plus 180, and a particle penetration of about 7 % or less, or of about 3 % or less or about 1 % or less.

[0168] In some embodiments, the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 63 g / m2to about 120 g / m2, a Gurley Hill porosity of about 2 seconds or more, a hydrostatic head from about y cmH2O to about 3000 cmH2O, wherein y is (2 times the Gurley Hill porosity value) plus 180, a particle penetration of about 7 % or less, and a Handle-O-Meter stiffness, normalized to basis weight, of about 30 mN / (g / m2) to about 70 mN / (g / m2).

[0169] In some embodiments, the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 63 g / m2to about 120 g / m2, a Gurley Hill porosity of about 2 seconds or more, a hydrostatic head from about y cmH2O to about 3000 cmH2O, wherein y is (2 times the Gurley Hill porosity value) plus 195, and a particle penetration of about 7 % or less, or about 3 % or less, or about 1 % or less.

[0170] In some embodiments, the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 63 g / m2to about 120 g / m2, a Gurley Hill porosity of about 2 seconds or more, a hydrostatic head from about y cmH2O to about 3000 cmH2O, wherein y is (2 times the Gurley Hill porosity value) plus 205, and a particle penetration of about 1 % or less.

[0171] In some embodiments, the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 15 g / m2to about 120 g / m2, a Gurley Hill porosity of about 20 seconds or more, a hydrostatic head from about p cmH2O to about 3000 cmH2O, wherein p is (2 times the Gurley Hill porosity value) plus 140, and a particle penetration of about 7 % or less, or of about 3 % or less, or of about 1 % or less.

[0172] In some embodiments, the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 15 g / m2to about 120 g / m2, a Gurley Hill porosity of about 20 seconds or more, a hydrostatic head from about p cmH2O to about 3000 cmH2O, wherein p is (2 times the Gurley Hill porosity value) plus 140, a particle penetration of about 7 % or less, of about 3 % or less, or of about 1 % or less, a Ret from about 2 m2Pa / W to about 10 m2Pa / W, and a blood barrier measured according to ISO 16603 of at least 1.75 kPa, or a viral barrier measured according to ISO 16604 of at least 0 kPa, or both, and optionally a resistance to chemical permeation, BT-i.o, measured according to ISO 6529 against 10 wt% NaOH of 120 min or above, or of 240 min or above, and a resistance to chemical permeation, BTi.o, measured according to ISO 6529 against 18 wt% H2SO4of 120 min or above, or of 240 min or above.In some embodiments, the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 15 g / m2to about 120 g / m2, a Gurley Hill porosity of about 20 seconds or more, a hydrostatic head from about p cmH2O to about 3000 cmH2O, wherein p is (2 times the Gurley Hill porosity value) plus 155 or plus 175 or plus 195, and a particle penetration of about 1 % or less.

[0173] In some embodiments, the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 30 g / m2to about 120 g / m2, a Gurley Hill porosity of about 20 seconds or more, a hydrostatic head from about p cmH2O to about 3000 cmH2O, wherein p is (2 times the Gurley Hill porosity value) plus 140, and a particle penetration of about 7 % or less, or of about 3 % or less, or of about 1 % or less.

[0174] In some embodiments, the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 30 g / m2to about 63 g / m2, a Gurley Hill porosity of about 20 seconds or more, a hydrostatic head from about p cmH2O to about 3000 cmH2O, wherein p is (2 times the Gurley Hill porosity value) plus 140, and a particle penetration of about 7 % or less, or of about 3 % or less, or of about 1 % or less.

[0175] In some embodiments, the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 30 g / m2to about 63 g / m2, a Gurley Hill porosity of about 20 seconds or more, a hydrostatic head from about p cmH2O to about 3000 cmH2O, wherein p is (2 times the Gurley Hill porosity value) plus 140, a particle penetration of about 7 % or less, or of about 3 % or less, or of about 1 % or less, and a Handle-O-Meter stiffness, normalized to basis weight, of about 4 mN / (g / m2) to about 30 mN / (g / m2).

[0176] In some embodiments, the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 30 g / m2to about 63 g / m2, a Gurley Hill porosity of about 20 seconds or more, a hydrostatic head from about p cmH2O to about 3000 cmH2O, wherein p is (2 times the Gurley Hill porosity value) plus 140, a particle penetration of about 7 % or less, or of about 3 % or less, or of about 1 % or less, and and a water vapor transmission rate (WVTR) from about 10,000 g / m2 / day to about 100,000 g / m2 / day.

[0177] In some embodiments, the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 30 g / m2to about 63 g / m2, a Gurley Hill porosity of about 20 seconds or more, a hydrostatic head from about p cmH2O to about 3000 cmH2O, wherein p is (2 times the Gurley Hill porosity value) plus 140, a particle penetration of about 7 % or less, or of about 3 % or less, or of about 1 % or less, a Handle-O-Meter stiffness, normalized to basis weight, of about 4 mN / (g / m2) to about 30 mN / (g / m2), and a water vapor transmission rate (WVTR) from about 10,000 g / m2 / day to about 100,000 g / m2 / day.In some embodiments, the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 63 g / m2to about 120 g / m2, a Gurley Hill porosity of about 20 seconds or more, a hydrostatic head from about p cmH2O to about 3000 cmH2O, wherein p is (2 times the Gurley Hill porosity value) plus 155, and a particle penetration of about 7 % or less, or of about 3 % or less, or of about 1 % or less.

[0178] In some embodiments, the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 63 g / m2to about 120 g / m2, a Gurley Hill porosity of about 20 seconds or more, a hydrostatic head from about p cmH2O to about 3000 cmH2O, wherein p is (2 times the Gurley Hill porosity value) plus 155, a particle penetration of about 7 % or less, or of about 3 % or less, or of about 1 % or less, and, a Handle-O-Meter stiffness, normalized to basis weight, of about 30 mN / (g / m2) to about 70 mN / (g / m2).

[0179] In some embodiments, the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 15 g / m2to about 48 g / m2, a Gurley Hill porosity from about 2 to about 20 seconds, a hydrostatic head from about m cmH2O to about 3000 cmH2O, wherein m is (2 times the Gurley Hill porosity value) plus 140, and a particle penetration of about 7 % or less, or of about 3 % or less, or of about 1 % or less.

[0180] In some embodiments, the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 15 g / m2to about 48 g / m2, a Gurley Hill porosity from about 2 to about 20 seconds, a hydrostatic head from about m cmH2O to about 3000 cmH2O, wherein m is (2 times the Gurley Hill porosity value) plus 140, a particle penetration of about 7 % or less, of about 3 % or less, or of about 1 % or less, a Ret from about 2 m2Pa / Wto about 10 m2Pa / W, and a blood barrier measured according to ISO 16603 of at least 1.75 kPa, or a viral barrier measured according to ISO 16604 of at least 0 kPa, or both, and optionally a resistance to chemical permeation, BT-i.o, measured according to ISO 6529 against 10 wt% NaOH of 120 min or above, or of 240 min or above, and a resistance to chemical permeation, BTi.o, measured according to ISO 6529 against 18 wt% H2SO4 of 120 min or above, or of 240 min or above.

[0181] In some embodiments, the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 30 g / m2to about 48 g / m2, a Gurley Hill porosity from about 2 to about 20 seconds, a hydrostatic head from about m cmH2O to about 3000 cmH2O, wherein m is (2 times the Gurley Hill porosity value) plus 140, and a particle penetration of about 7 % or less, or of about 3 % or less, or of about 1 % or less.

[0182] In some embodiments, the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 15 g / m2to about48 g / m2, a Gurley Hill porosity from about 2 to about 10 seconds, a hydrostatic head from about m cmH2O to about 3000 cmH2O, wherein m is (2 times the Gurley Hill porosity value) plus 140, and a particle penetration of about 7 % or less, or of about 3 % or less, or of about 1 % or less.

[0183] In some embodiments, the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 30 g / m2to about 48 g / m2, a Gurley Hill porosity from about 2 to about 10 seconds, a hydrostatic head from about m cmH2O to about 3000 cmH2O, wherein m is (2 times the Gurley Hill porosity value) plus 140, and a particle penetration of about 7 % or less, or of about 3 % or less, or of about 1 % or less.

[0184] In some embodiments, the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 30 g / m2to about 48 g / m2, a Gurley Hill porosity from about 2 to about 20 seconds, a hydrostatic head from about m cmH2O to about 3000 cmH2O, wherein m is (2 times the Gurley Hill porosity value) plus 155, and a particle penetration of about 7 % or less, or of 3 % or less, or of about 1 % or less.

[0185] In some embodiments, the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 30 g / m2to about 48 g / m2, a Gurley Hill porosity from about 2 to about 10 seconds, a hydrostatic head from about m cmH2O to about 3000 cmH2O, wherein m is (2 times the Gurley Hill porosity value) plus 155, and a particle penetration about 7 % or less, or of 3 % or less, or of about 1 % or less.

[0186] In some embodiments, the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 15 g / m2to about 48 g / m2, a Gurley Hill porosity from about 2 to about 6 seconds, a hydrostatic head from about m cmH2O to about 3000 cmH2O, wherein m is (2 times the Gurley Hill porosity value) plus 140, and a particle penetration of about 5 % or less, or of about 3 % or less, or of about 1 % or less.

[0187] In some embodiments, the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 30 g / m2to about 48 g / m2, a Gurley Hill porosity from about 2 to about 6 seconds, a hydrostatic head from about m cmH2O to about 3000 cmH2O, wherein m is (2 times the Gurley Hill porosity value) plus 140, and a particle penetration of about 5 % or less, or of about 3 % or less, or of about 1 % or less.

[0188] In some embodiments, the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 15 g / m2to about 48 g / m2, a Gurley Hill porosity from about 2 to about 6 seconds, a hydrostatic head from aboutm cmH2O to about 3000 cmH20, wherein m is (2 times the Gurley Hill porosity value) plus 140, a particle penetration of about 5 % or less, or of about 3 % or less, or of about 1 % or less, and a Handle-O-Meter stiffness, normalized to basis weight, of about 4 mN / (g / m2) to about 20 mN / (g / m2).

[0189] In some embodiments, the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 30 g / m2to about 48 g / m2, a Gurley Hill porosity from about 2 to about 6 seconds, a hydrostatic head from about m cmH2O to about 3000 cmH2O, wherein m is (2 times the Gurley Hill porosity value) plus 140, a particle penetration of about 5 % or less, or of about 3 % or less, or of about 1 % or less, and a Handle-O-Meter stiffness, normalized to basis weight, of about 4 mN / (g / m2) to about 20 mN / (g / m2).

[0190] In some embodiments, the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 15 g / m2to about 48 g / m2, a Gurley Hill porosity from about 2 to about 6 seconds, a hydrostatic head from about m cmH20 to about 3000 cmH2O, wherein m is (2 times the Gurley Hill porosity value) plus 140, a particle penetration of about 5 % or less, and a water vapor transmission rate (WVTR) from about 30,000 g / m2 / day to about 100,000 g / m2 / day, or from about 40,000 g / m2 / day to about 100,000 g / m2 / day.

[0191] In some embodiments, the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 30 g / m2to about 48 g / m2, a Gurley Hill porosity from about 2 to about 6 seconds, a hydrostatic head from about m cmH2O to about 3000 cmH2O, wherein m is (2 times the Gurley Hill porosity value) plus 140, a particle penetration of about 5 % or less, and a water vapor transmission rate (WVTR) from about 30,000 g / m2 / day to about 100,000 g / m2 / day, or from about 40,000 g / m2 / day to about 100,000 g / m2 / day.

[0192] In some embodiments, the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 15 g / m2to about 48 g / m2, a Gurley Hill porosity from about 2 to about 6 seconds, a hydrostatic head from about m cmH2O to about 3000 cmH2O, wherein m is (2 times the Gurley Hill porosity value) plus 140, a particle penetration of about 5 % or less, a Handle-O-Meter stiffness, normalized to basis weight, of about 4 mN / (g / m2) to about 20 mN / (g / m2), and a water vapor transmission rate (WVTR) from about 30,000 g / m2 / day to about 100,000 g / m2 / day, or from about 40,000 g / m2 / day to about 100,000 g / m2 / day.

[0193] In some embodiments, the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 30 g / m2to about 48 g / m2, a Gurley Hill porosity from about 2 to about 6 seconds, a hydrostatic head from about m cmH2O to about 3000 cmH2O, wherein m is (2 times the Gurley Hill porosity value) plus140, a particle penetration of about 5 % or less, a Handle-O-Meter stiffness, normalized to basis weight, of about 4 mN / (g / m2) to about 20 mN / (g / m2), and a water vapor transmission rate (WVTR) from about 30,000 g / m2 / day to about 100,000 g / m2 / day, or from about 40,000 g / m2 / day to about 100,000 g / m2 / day.

[0194] In some embodiments, the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 15 g / m2to about 48 g / m2, a hydrostatic head of about 160 cmH2O or more, a particle penetration of about 5 % or less, or of about 3 % or less, or of about 1 % or less, and a water vapor transmission rate (WVTR) from about 20,000 g / m2 / day to about 100,000 g / m2 / day.

[0195] In some embodiments, the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 15 g / m2to about 48 g / m2, a hydrostatic head of about 160 cmH2O or more, a particle penetration of about 5 % or less, of about 3 % or less, or of about 1 % or less, a water vapor transmission rate (WVTR) from about 20,000 g / m2 / day to about 100,000 g / m2 / day, a Ret from about 2 m2Pa / W to about 10 m2Pa / W, and a blood barrier measured according to ISO 16603 of at least 1.75 kPa, or a viral barrier measured according to ISO 16604 of at least 0 kPa, or both, and optionally a resistance to chemical permeation, BT1 0, measured according to ISO 6529 against 10 wt% NaOH of 120 min or above, or of 240 min or above, and a resistance to chemical permeation, BTi o, measured according to ISO 6529 against 18 wt% H2SO4of 120 min or above, or of 240 min or above.

[0196] In some embodiments, the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 15 g / m2to about 48 g / m2, a hydrostatic head of about 180 cmH2O or more, a particle penetration of about 5 % or less, or of about 3 % or less, or of about 1 % or less, and a water vapor transmission rate (WVTR) from about 20,000 g / m2 / day to about 100,000 g / m2 / day.

[0197] In some embodiments, the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 15 g / m2to about 48 g / m2, a hydrostatic head of about 160 cmH2O or more, a particle penetration of about 5 % or less, and a water vapor transmission rate (WVTR) from about 20,000 g / m2 / day to about 100,000 g / m2 / day, and a Handle-O-Meter stiffness, normalized to basis weight, of about 4 mN / (g / m2) to about 30 mN / (g / m2).

[0198] In some embodiments, the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 30 g / m2to about 48 g / m2, a hydrostatic head of about 160 cmH2O or more, a particle penetration of about 5 % or less, or of about 3 % or less, or of about 1 % or less, and a water vapor transmission rate (WVTR) from about 20,000 g / m2 / day to about 100,000 g / m2 / day.In some embodiments, the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 30 g / m2to about 48 g / m2, a hydrostatic head of about 160 cmH2O or more, a particle penetration of about 5 % or less, or of about 3 % or less, or of about 1 % or less, and a water vapor transmission rate (WVTR) from about 40,000 g / m2 / day to about 100,000 g / m2 / day.

[0199] In some embodiments, the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 30 g / m2to about 48 g / m2, a hydrostatic head of about 200 cmH2O or more, a particle penetration of about 1 % or less, a water vapor transmission rate (WVTR) from about 20,000 g / m2 / day to about 100,000 g / m2 / day, or from about 40,000 g / m2 / day to about 100,000 g / m2 / day.

[0200] In some embodiments, the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 15 g / m2to about 120 g / m2, a hydrostatic head of about 220 cmH2O or more, a particle penetration of about 1 % or less, and a water vapor transmission rate (WVTR) from about 10,000 g / m2 / day to about 100,000 g / m2 / day, or from about 40,000 g / m2 / day to about 100,000 g / m2 / day.

[0201] In some embodiments, the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 15 g / m2to about 120 g / m2, a hydrostatic head of about 220 cmH2O or more, a particle penetration of about 1 % or less, a water vapor transmission rate (WVTR) from about 10,000 g / m2 / day to about 100,000 g / m2 / day, or from about 40,000 g / m2 / day to about 100,000 g / m2 / day, a Ret from about 2 m2Pa / W to about 10 m2Pa / W, and a blood barrier measured according to ISO 16603 of at least 1.75 kPa, or a viral barrier measured according to ISO 16604 of at least 0 kPa, or both, and optionally a resistance to chemical permeation, BT-i.o, measured according to ISO 6529 against 10 wt% NaOH of 120 min or above, or of 240 min or above, and a resistance to chemical permeation, BTij0, measured according to ISO 6529 against 18 wt% H2SO4of 120 min or above, or of 240 min or above.

[0202] In some embodiments, the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 15 g / m2to about 120 g / m2, a hydrostatic head of about 220 cmH2O or more, a particle penetration of about 1 % or less, or of about 0.1 % or less, and a water vapor transmission rate (WVTR) from about 10,000 g / m2 / day to about 100,000 g / m2 / day.

[0203] In some embodiments, the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 15 g / m2to about 120 g / m2, a hydrostatic head of about 220 cmH2O or more, a particle penetration of about 1 % or less, or of about 0.1 % or less, and a water vapor transmission rate (WVTR) from about 20,000 g / m2 / day to about 100,000 g / m2 / day.In some embodiments, the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 48 g / m2to about 120 g / m2, a hydrostatic head of about 220 cmH2O or more, a particle penetration of about 1 % or less, a water vapor transmission rate (WVTR) from about 10,000 g / m2 / day to about 100,000 g / m2 / day, and a Handle-O-Meter stiffness, normalized to basis weight, of about 30 mN / (g / m2) to about 70 mN / (g / m2).

[0204] Applicant has found that the bonded sheets according to the invention surprisingly have a very good balance of high gas permeability, low liquid permeability, and good protection properties. The sheets according to the invention may further have a moderate degree of softness, which makes them very suitable for use in packaging, including, but not limited to, protective clothing, outdoor and sports apparel, active packaging, covers for equipment including car covers, cargo covers, and further applications.

[0205] Preparation of Bonded Sheet of Nonwoven Flash-spun Plexifilamentary Fibrils of Polymer

[0206] Flash-Spinning, Collecting, and Consolidating

[0207] Flash-spinning is a method for producing fibrils having a unique plexifilamentary structure. It involves preparing a solution of a fibril-forming polymer in a spin agent (the spin fluid) at a pressure above the vapor pressure of the spin agent and at a temperature above the normal boiling point of the spin agent, and releasing that spin fluid into a zone of substantially lower temperature and pressure such that the spin agent flash evaporates and the polymer solidifies in the form of plexifilamentary fibrils. Suitable flash spinning processes and equipment which can be used herein are described in US 3,081,519, US 3,227,794, US 3,860,369, and US 7,744,989.

[0208] The formed plexifilamentary fibrils of polymer are discharged from each spin orifice, and the shape of these plexifilamentary fibrils of polymer may be modified by any methods known in the art. In some embodiments, the plexifilamentary fibrils of polymer discharged from each spin orifice may be modified by passing into a shroud such as described on US 3,387,326, in other embodiments by passing into a slotted outlet such as described in US 3,467,744 or US 5,788,993, and in other embodiments by passing into a slot fan jet as described in US 8,114,325. In some embodiments, streams of fibrils from multiple orifices may exit via a common slot as described in US 3,564,088.

[0209] Sheets comprising plexifilamentary fibrils of polymer can be formed by any method known in the art. In some embodiments, the stream of fibrils discharged from each spin orificeis directed towards a deflector device which alternately directs the stream of fibrils to the left and right onto a moving collecting device such that the fibrils accumulate in the form of a sheet, formed from fibrils oriented in an overlapping, multi-directional configuration. Deflection of the stream of fibrils may be achieved by any suitable means known in the art, including, but not limited to, those described in US 3,277,526 and US 3,387,326, US 3,169,899, US 3,497,918, US 3,593,074, US 3,851 ,023 and US 3,860,369, US 4,148,595, US 5,045,258, US 5,643,524, US 5,731 ,011 , US 5,750,152 and WO 92 / 20511 A1. The stream of fibrils may also be laid down to form a sheet without deflection as described in US 5,788,993 and US 8, 114,325. The method of forming a sheet may further utilize structures in the spin cell such as those described in US 5,123,983, US 5,296,172, and WO 92 / 20511 A1. In some embodiments, the sheet may comprise both continuous flash-spun plexifilamentary fibrils and flash-spun discontinuous, cut, staple, or pulped fibers. In other embodiments, the sheet may comprise flash-spun discontinuous, cut, staple, or pulped fibers.

[0210] In some embodiments, the streams of fibrils are discharged from spin orifices located on a rotating support, and the fibrils are collected on a collecting belt which surrounds the rotating arrangement circumferentially as described in US 7,118,698, US 7,621 ,731, US 7,786,034, and US 7,998,388.

[0211] In one embodiment, the process for the preparation of a sheet of nonwoven flash-spun plexifilamentary fibrils comprises the steps of:

[0212] (i) generating a spin fluid comprising

[0213] (a) from about 8 to about 20 weight percent of a polymer, based on the total amount of the spin fluid, and

[0214] (b) a spin agent comprising one or more hydrocarbons,

[0215] (ii) flash spinning the spin fluid at a temperature at or above about 190 °C and at a pressure that is above the vapor pressure of the spin fluid into a region of essentially atmospheric pressure to form plexifilamentary fibrils of the polymer,

[0216] (iii) collecting the plexifilamentary fibrils of the polymer on a collecting means as a sheet of nonwoven flash-spun plexifilamentary fibrils and applying pressure to the sheet to obtain a consolidated sheet,

[0217] (iv) pre-bonding the sheet by warm compression pre-bonding, and

[0218] (vi) thermal bonding by whole surface contact bonding of the pre-bonded sheet.

[0219] The sheet formed by flash-spinning as described herein may be consolidated by applying a small amount of pressure to the sheet. In some embodiments, the sheet may be passed under a roller which applies pressure to the sheet to form a consolidated sheet.

[0220] In some embodiments, the polymer used in the process described herein may be polyethylene (PE), in particular high-density polyethylene (HDPE), or blends / mixtures of high-density polyethylene (HDPE) with low-density polyethylene (LDPE), in particular blends / mixtures of high-density polyethylene (HDPE) with linear low-density polyethylene (LLDPE). In some embodiments, the polymer comprises at least 40 weight percent of high-density polyethylene (HDPE), based on the total amount of polymer. In other embodiments, the polymer comprises at least 60 weight percent of high-density polyethylene (HDPE), based on the total amount of polymer, and in other embodiments, the polymer comprises at least 90 weight percent of high-density polyethylene (HDPE), based on the total amount of polymer.

[0221] Process with one or more hydrocarbons as spin agent

[0222] In some embodiments, the spin agent may include one or more hydrocarbons. In some embodiments, the spin fluid comprises the polymer in an amount of from about 8 to about 20 weight percent, based on the total amount of the spin fluid, in other embodiments, the spin fluid comprises the polymer in an amount from about 10 to about 18 weight percent, based on the total amount of the spin fluid, and in other embodiments, the spin fluid comprises the polymer in an amount from about 12 to about 15 weight percent, based on the total amount of the spin fluid.

[0223] In some embodiments, the spin fluid comprises the spin agent in an amount of from about 80 to about 92 weight percent, based on the total amount of the spin fluid, in other embodiments, the spin fluid comprises the spin agent in an amount from about 82 to about 90 weight percent, based on the total amount of the spin fluid, and in other embodiments, the spin fluid comprises the spin agent in an amount from about 85 to about 88 weight percent, based on the total amount of the spin fluid.

[0224] In some embodiments, the flash-spinning is performed at a temperature of 190 °C or above, in other embodiments at a temperature of 200 °C or above, in other embodiments at a temperature of 205 °C or above, and in other embodiments at a temperature of 210 °C or above. In some embodiments, the flash-spinning is performed at a temperature from about 190 °C to about 220 °C.

[0225] In some embodiments, the spin agent comprises one or more hydrocarbons. In some embodiments, the one or more hydrocarbons of the spin agent are selected from n-pentane, cyclopentane, hexane, cyclohexane, 2-methylbutane, 2-methylpentane, 3-methylpentane, 2,2-dimethylbutane, or mixtures thereof. In some embodiments, the spin agent comprises n-pentane, cyclopentane or a mixture thereof. In some embodiments, the spin agent consists essentially of or consists of n-pentane. In some embodiments, the spin agent comprises, consists essentially of, or consists of a mixture of n-pentane and cyclopentane, in other embodiments, the spin agent comprises, consists essentially of, or consists of from about 60 to about 90 weight percent n-pentane and from about 40 to about 10 weight percent cyclopentane, in other embodiments from about 60 to about 80 weight percent n-pentane andfrom about 40 to about 20 weight percent cyclopentane. In some embodiments, the spin agent comprises, consists essentially of, or consists of a mixture of n-pentane, cyclopentane, and branched hydrocarbon with 5 or 6 carbon atoms. In some embodiments, the spin agent comprises or consists essentially of a mixture of (1) n-pentane, (2) cyclopentane, and (3) 2-methylbutane, 2-methylpentane, 3-methylpentane, or 2,2-dimethylbutane. In some embodiments, the spin agent comprises, consists essentially of, or consist of a mixture of (1) n-pentane, (2) cyclopentane, and (3) 2-methylbutane, 2-methylpentane, 3-methylpentane, or 2,2-dimethylbutane. In some embodiments, the spin agent comprises, consists essentially of, or consist of a mixture of (1) from about 60 to about 85 weight percent n-pentane, (2) from about 13 to about 33 weight percent cyclopentane, and (3) from about 2 to about 7 weight percent 2,2-dimethylbutane, 2-methylpentane, 3-methylpentane, or 2,2-dimethylbutane.

[0226] The spin fluid may include additives, such as antioxidants or acid scavengers in minor amounts. In some embodiments, the spin fluid comprises additives in an amount of about 1.5 weight percent or less, based on the total amount of the spin fluid, and in other embodiments in an amount of about 0.1 weight percent or less, based on the total amount of the spin fluid.

[0227] In some embodiments, the plexifilamentary fibrils are spun at a spin temperature from about 190 °C to about 220 °C using a spin fluid comprising about 8 to about 20 weight percent polymer, based on the total amount of the spin fluid, and comprising a spin agent which comprises, consists essentially of, or consists of n-pentane.

[0228] Process with the mixture of chlorine- and fluorine-containing solvents

[0229] The spin agent may include a chlorine-containing solvent, selected from dichloromethane, cis-1,2-dichloroethylene, trans- 1 ,2-dichloroethylene, or a mixture of cis-1 ,2-dichloroethylene and trans-1 ,2-dichloroethylene, in combination with a fluorine-containing solvent. In some embodiments, the spin fluid comprises the polymer in an amount from about 8.0 to about 11.0 weight percent, based on the total amount of the spin fluid, in other embodiments, the spin fluid comprises the polymer in an amount from about 8.0 to about 10.5 weight percent, based on the total amount of the spin fluid, in other embodiments, the spin fluid comprises the polymer in an amount from about 8.0 to about 10.0 weight percent, based on the total amount of the spin fluid, and in other embodiments, the spin fluid comprises the polymer in an amount from about 9.0 to about 11.0 weight percent, based on the total amount of the spin fluid.

[0230] In some embodiments, the spin fluid comprises the spin agent in an amount from about 89.0 to about 92.0 weight percent, based on the total amount of the spin fluid, in other embodiments, the spin fluid comprises the spin agent in an amount from about 89.5 to about 92.0 weight percent, based on the total amount of the spin fluid, in other embodiments, thespin fluid comprises the spin agent in an amount from about 90.0 to about 92.0 weight percent, based on the total amount of the spin fluid, and in other embodiments, the spin fluid comprises the spin agent in an amount from about 89.0 to about 91.0 weight percent, based on the total amount of the spin fluid.

[0231] In some embodiments, the flash-spinning is performed at a temperature from about 195 °C to about 230 °C, and in other embodiments, from about 200 °C to about 220 °C, in other embodiments, from about 205 °C to about 220 °C, and in other embodiments, from about 210 °C to about 220 °C.

[0232] In some embodiments, the spin agent comprises a chlorine-containing solvent, selected from dichloromethane, cis-1 ,2-dichloroethylene, trans-1 ,2-dichloroethylene or a mixture of cis-1 ,2-dichloroethylene and trans-1 ,2-dichloroethylene, in combination with a fluorine-containing solvent. In some embodiments, the spin agent comprises a chlorine-containing solvent, selected from dichloromethane, cis-1 ,2-dichloroethylene, trans-1 ,2-dichloroethylene, or a mixture of cis-1 ,2-dichloroethylene and trans-1,2-dichloroethylene, in combination with a fluorine-containing solvent which is a linear hydrofluorocarbon having three to six carbon atoms, a cyclic hydrofluorocarbon having four to five carbon atoms, a perfluorocarbon having five to six carbon atoms, ora hydrofluoroether. In some embodiments, the linear hydrofluorocarbons having three to six carbon atoms of the spin agent are 1 ,1 ,1 ,3,3-pentafluorobutane, 1H,4H-octafluorobutane, 2H,3H-decafluoropentane, 1H-tridecafluorohexane, or 1H,6H-dodecafluorohexane. In some embodiments, the cyclic hydrofluorocarbons having four to five carbon atoms of the spin agent are cis-1H,2H-octafluorocyclopentane, trans-1H,2H-octafluorocyclopentane, a mixture of cis-1H,2H-octafluorocyclopentane and trans-1H,2H-octafluorocyclopentane, 1H,1H,2H-heptafluorocyclopentane, or 1,1,2,2,3,3-hexafluorocyclopentane. In some embodiments, the hydrofluoroethers of the spin agent are 1 -methoxynonafluorobutane or 1-ethoxynonafluorobutane.

[0233] In some embodiments, the spin agent comprises, consists essentially, or consists of a mixture of (1) dichloromethane and (2) 1 ,1 ,1 ,3,3-pentafluorobutane, 1H,4H-octafluorobutane, 2H,3H-decafluoropentane, 1H-tridecafluorohexane, or 1H,6H-dodecafluorohexane. In some embodiments, the spin agent comprises, consists essentially, or consists of (1) from about 70 to about 85 weight percent dichloromethane and (2) from about 15 to about 30 weight percent 1 ,1 ,1 ,3,3-pentafluorobutane, 1H,4H-octafluorobutane, 2H,3H-decafluoropentane, 1H-tridecafluorohexane, or 1H,6H-dodecafluorohexane, and in other embodiments, (1) from about 75 to about 85 weight percent dichloromethane and (2) from about 15 to about 25 weight percent 1,1,1,3,3-pentafluorobutane, 1H,4H-octafluorobutane, 2H,3H-decafluoropentane, 1H-tridecafluorohexane, or 1H,6H-dodecafluorohexane.In some embodiments, the spin agent comprises, consists essentially, or consists of a mixture of (1) dichloromethane and (2) cis-1H,2H-octafluorocyclopentane, trans-1H,2H-octafluorocyclopentane, a mixture of cis-1H,2H-octafluorocyclopentane and trans-1H,2H-octafluorocyclopentane, 1H,1H,2H-heptafluorocyclopentane, or 1, 1,2, 2,3,3-hexafluorocyclopentane. In some embodiments, the spin agent comprises, consists essentially, or consists of (1) from about 65 to about 80 weight percent dichloromethane and (2) from about 20 to about 35 weight percent cis-1H,2H-octafluorocyclopentane, trans-1H,2H-octafluorocyclopentane, a mixture of cis-1H,2H-octafluorocyclopentane and trans-1H,2H-octafluorocyclopentane, 1H,1H,2H-heptafluorocyclopentane, or 1, 1,2, 2,3,3-hexafluorocyclopentane, and in other embodiments, (1) from about 65 to about 75 weight percent dichloromethane and (2) from about 25 to about 35 weight percent cis-1H,2H-octafluorocyclopentane, trans-1H,2H-octafluorocyclopentane, a mixture of cis-1H,2H-octafluorocyclopentane and trans-1H,2H-octafluorocyclopentane, 1H,1H,2H-heptafluorocyclopentane, or 1,1,2,2,3,3-hexafluorocyclopentane.

[0234] In some embodiments, the spin agent comprises, consists essentially, or consists of a mixture of (1) 1,2-dichloroethylene and (2) 1,1,1,3,3-pentafluorobutane, 1H,4H-octafluorobutane, 2H,3H-decafluoropentane, 1H-tridecafluorohexane, or 1H,6H-dodecafluorohexane. In some embodiments, the spin agent comprises, consists essentially, or consists of (1) from about 70 to about 85 weight percent 1,2-dichloroethylene and (2) from about 15 to about 30 weight percent 1,1,1,3,3-pentafluorobutane, 1H,4H-octafluorobutane, 2H,3H-decafluoropentane, 1H-tridecafluorohexane, or 1H,6H-dodecafluorohexane, and in other embodiments, (1) from about 70 to about 80 weight percent 1,2-dichloroethylene and (2) from about 20 to about 30 weight percent 1,1,1,3,3-pentafluorobutane, 1H,4H-octafluorobutane, 2H,3H-decafluoropentane, 1H-tridecafluorohexane, or 1H,6H-dodecafluorohexane.

[0235] In some embodiments, the spin agent comprises, consists essentially, or consists of a mixture of (1) 1,2-dichloroethylene and (2) cis-1H,2H-octafluorocyclopentane, trans-1H,2H-octafluorocyclopentane, a mixture of cis-1H,2H-octafluorocyclopentane and trans-1H,2H-octafluorocyclopentane, 1H,1H,2H-heptafluorocyclopentane, or 1, 1,2, 2,3,3-hexafluorocyclopentane. In some embodiments, the spin agent comprises, consists essentially, or consists of (1) from about 65 to about 80 weight percent 1,2-dichloroethylene and (2) from about 20 to about 35 weight percent cis-1H,2H-octafluorocyclopentane, trans-1H,2H-octafluorocyclopentane, a mixture of cis-1H,2H-octafluorocyclopentane and trans-1H,2H-octafluorocyclopentane, 1H,1H,2H-heptafluorocyclopentane or 1, 1,2, 2,3,3-hexafluorocyclopentane, and in other embodiments, (1) from about 65 to about 75 weight percent 1,2-dichloroethylene and (2) from about 20 to about 30 weight percent cis-1H,2H-octafluorocyclopentane, trans-1H,2H-octafluorocyclopentane, a mixture of cis-1H,2H-octafluorocyclopentane and trans-1H,2H-octafluorocyclopentane, 1H,1H,2H-heptafluorocyclopentane, or 1 ,1 ,2,2, 3, 3-hexafluorocyclopentane.

[0236] In some embodiments, the spin agent comprises, consists essentially, or consists of a mixture of (1) trans-1,2-dichloroethylene and (2) 1 ,1 ,1 ,3,3-pentafluorobutane, 1H,4H-octafluorobutane, 2H,3H-decafluoropentane, 1H-tridecafluorohexane, or 1H,6H-dodecafluorohexane. In some embodiments, the spin agent comprises, consists essentially, or consists of (1) from about 70 to about 85 weight percent trans-1 ,2-dichloroethylene and (2) from about 15 to about 30 weight percent 1 ,1 ,1 ,3,3-pentafluorobutane, 1H,4H-octafluorobutane, 2H,3H-decafluoropentane, 1H-tridecafluorohexane, or 1H,6H-dodecafluorohexane, and in other embodiments, (1) from about 70 to about 80 weight percent trans- 1,2-dichloroethylene and (2) from about 20 to about 30 weight percent 1 ,1 , 1 ,3, 3-pentafluorobutane, 1H,4H-octafluorobutane, 2H,3H-decafluoropentane, 1H-tridecafluorohexane, or 1H,6H-dodecafluorohexane.

[0237] In some embodiments, the spin agent comprises, consists essentially, or consists of a mixture of (1) trans-1 , 2-dichloroethylene and (2) 1H,2H-octafluorocyclopentane, cis-1H,2H-octafluorocyclopentane, trans-1 H,2H-octafluorocyclopentane, 1 H,1 H,2H-heptafluorocyclopentane, or 1,1, 2, 2, 3, 3-hexafluorocyclopentane. In some embodiments, the spin agent comprises, consists essentially, or consists of (1) from about 65 to about 80 weight percent trans-1 ,2-dichloroethylene and (2) from about 20 to about 35 weight percent cis-1H,2H-octafluorocyclopentane, trans-1 H,2H-octafluorocyclopentane, a mixture of cis-1H,2H-octafluorocyclopentane and trans-1 H,2H-octafluorocyclopentane, 1H,1H,2H-heptafluorocyclopentane, or 1,1, 2, 2, 3, 3-hexafluorocyclopentane, and in other embodiments, (1) from about 65 to about 75 weight percent trans-1 ,2-dichloroethylene and (2) from about 20 to about 30 weight percent 1 H,2H-octafluorocyclopentane, cis-1 H,2H-octafluorocyclopentane, trans-1H,2H-octafluorocyclopentane, 1H,1H,2H-heptafluorocyclopentane, or 1 , 1 ,2, 2,3,3-hexafluorocyclopentane.

[0238] In some embodiments, the spin agent comprises, consists essentially, or consists of a mixture of (1) dichloromethane and (2) 1 -methoxynonafluorobutane or 1-ethoxynonafluorobutane. In some embodiments, the spin agent comprises, consists essentially, or consists of (1) from about 70 to about 85 weight percent dichloromethane and (2) from about 15 to about 30 weight percent 11 -methoxynonafluorobutane or 1-ethoxynonafluorobutane, and in other embodiments, (1) from about 70 to about 80 weight percent dichloromethane and (2) from about 20 to about 30 weight percent 1-methoxynonafluorobutane or 1 -ethoxynonafluorobutane.

[0239] The spin fluid may include additives, such as antioxidants or acid scavengers in minor amounts. In some embodiments, the spin fluid comprises additives in an amount of about1.5 weight percent or less of the total amount of the spin fluid, and in other embodiments in an amount of about 0.1 weight percent or less of the total amount of the spin fluid.

[0240] In some embodiments, the plexifilamentary fibrils are spun at a spin temperature from about 195 °C to about 230 °C using a spin fluid comprising about 8.0 to about 11.0 weight percent polymer. In some embodiments, the plexifilamentary fibrils are spun at a spin temperature from about 200 °C to about 220 °C using a spin fluid comprising about 8.0 to about 11.0 weight percent polymer. In some embodiments, the plexifilamentary fibrils are spun at a spin temperature from about 205 °C to about 230 °C using a spin fluid comprising about 8.0 to about 11.0 weight percent polymer. In some embodiments, the plexifilamentary fibrils are spun at a spin temperature from about 210 °C to about 220 °C using a spin fluid comprising about 8.0 to about 11.0 weight percent polymer. In some embodiments, the plexifilamentary fibrils are spun at a spin temperature from about 210 °C to about 220 °C using a spin fluid comprising about 8.0 to about 10.5 weight percent polymer. In some embodiments, the plexifilamentary fibrils are spun at a spin temperature from about 205 °C to about 230 °C using a spin fluid comprising about 8.0 to about 10.0 weight percent polymer. In some embodiments, the plexifilamentary fibrils are spun at a spin temperature from about 210 °C to about 220 °C using a spin fluid comprising about 8.0 to about 10.0 weight percent polymer.

[0241] Warm Compression Pre-Bonding and Thermal Bonding

[0242] After the flash-spun sheet is formed into a consolidated sheet as described herein, the consolidated sheet is then subjected to a warm compression pre-bonding step followed by thermal bonding. Warm compression pre-bonding is performed using low to moderate heat and pressure to compress the sheet without melting the fiber network. In some embodiments, the heat and compression steps of the pre-bonding step are simultaneous. In other embodiments, the heat and compression steps of the pre-bonding step are sequential, such that the sheet is still warm from the heating step when it is subjected to compression.

[0243] In some embodiments, the warm compression pre-bonding step is performed by heating the consolidated sheet to a temperature between the melting extrapolated onset temperature minus 85 °C (Teim- 85 °C) and the melting extrapolated onset temperature (Teim) in °C of the polymer comprised in the sheet and under a pressure from about 1 to about 50 bar, about 1 to about 30 bar, about 1 bar to about 15 bar, or about 5 bar to about 15 bar. In some embodiments, the warm compression pre-bonding step is performed by heating the consolidated sheet to a temperature between the melting extrapolated onset temperature minus 65 °C (Teim- 65 °C) and the melting extrapolated onset temperature (Teim) in °C of the polymer comprised in the sheet and under a pressure of about 1 bar to about 15 bar.The warm compression pre-bonding step as described herein may allow the sheet density to be altered without thermally bonding. In some embodiments, a heated platen press may be used to perform the warm compression pre-bonding step.

[0244] For example, high density polyethylene has a melting extrapolated onset temperature (Teim) from about 120 to about 125 °C. For other polyolefins, such as other polyethylenes or polypropylenes, other melting extrapolated onset temperatures may apply.

[0245] In some embodiments, when the sheet is comprised of high density polyethylene fibres, the sheet is heated to a temperature from about 35 °C to about 125 °C, or from about 45 °C to about 125 °C, or from about 50 °C to about 125 °C at a pressure from about 1 bar to about 50 bar or from about 5 to about 15 bar. The residence time is appropriately selected to allow the heating to occur through the thickness of the sheet without melting the fibers to create a bonded sheet.

[0246] In some embodiments, the warm compression pre-bonding step is performed using one or more calender nips to apply heat and pressure to the sheet at a temperature from about Teim - 85 °C to about Teim of the polymer comprised in the sheet and at a pressure from about 1 bar to about 50 bar or from about 1 bar to about 30 bar or from about 1 bar to about 15 bar or from about 5 bar to about 15 bar. In some embodiments, the surfaces of the sheet may be alternately or concurrently in contact with a heated roll. In some embodiments, the calender roll may include an adjustable wrap roll for adjusting the length of the heated calender roll over which the sheet passes. In some embodiments, the heated calender roll may include one or more back-up rolls which may be heated or unheated. In some embodiments, the calender nip includes a smooth surface or a patterned surface. In some embodiments, the calender nip may be enclosed in a heated box in which the air is heated to add heat to the sheet.

[0247] In some embodiments, the warm compression pre-bonding step is performed using a continuous through-feed hot press to apply heat and pressure to the sheet at a temperature from Tam - 85 °C to about Teim of the polymer comprised in the sheet and at a pressure from about 1 to 50 bar or from about 1 to 30 bar or from about 1 to 15 bar. In some embodiments, a double belt press is used as the continuous through-feed hot press, where two continuous heated belts move in parallel over rolls.

[0248] The pre-bonding step is then followed by thermal bonding. In some embodiments, the thermal bonding is performed as a whole surface bonding step as described for example in US 3,442,740, US 3,532,589 and US 5,068,796, where the fabric is heated without the presence of substantial pressure, and US 5,972,147 where the fabric is heated through a series of pre-heating rolls followed by a step of calendering the surface.In some embodiments, the thermal bonding follows the pre-bonding step either directly or in a separate step. In some embodiments, there can be one or more further steps between the warm compression pre-bonding step and the thermal bonding step.

[0249] In some embodiments, the thermal bonding is performed at a temperature sufficient to melt the fibrils to create the bonded sheet. In some embodiments, the thermal bonding is performed at a temperature between the melting point (Tm) in °C of the polymer comprised in the sheet and the melting point minus 7 °C (Tm- 7 °C)

[0250] For example, high density polyethylene has a melting point of about 130 °C to about 135 °C. For other polyolefins, such as other polyethylenes or polypropylenes, other melting points may apply.

[0251] In some embodiments, when the sheet is comprised of high density polyethylene fibres, the sheet thermally bonded at a temperature from about 128 °C to about 135 °C. In some embodiments, a heated platen press may be used to perform the thermal bonding.

[0252] In some embodiments, the thermal bonding is performed by additionally applying a pressure from about 0.01 to about 1 bar.

[0253] Uses, Multilayer Structures, and Articles

[0254] The sheet of nonwoven flash-spun plexifilamentary fibrils as described herein has many uses and may be used in a variety of applications, including, but not limited to, protective clothing, outdoor and sports apparel, active packaging, covers for equipment including car covers, and cargo covers.

[0255] In some embodiments, the article is selected from protective clothing, protective covers, gowns, drapes, shoe covers, operating back-table covers, equipment covers for operating processes, equipment covers for biological and drug manufacturing processes, portable biohazard tents and enclosures, isolation fabrics, emergency shelters, mobile operating containment enclosures, sterilization wraps, and other applications relating to healthcare, emergency, first responder and biohazard protection.

[0256] Healthcare, emergency, first responder, and biohazard protection applications often require a high flux to allow rapid exhaust of warm air, water vapor, or sterilization gases, while having high barrier properties to blood and viral pathogens to ensure the protection of the operating utensils, the protected area, and healthcare equipment, and to ensure the protection of the wearer to biological hazards.

[0257] In some embodiments, the article comprising a sheet of nonwoven flash-spun plexifilamentary fibrils can be used for protective clothing. Protective clothing includes, but is not limited to, industrial, military, and medical protective clothing applications. Many of these protective clothing applications often require barrier protection against liquids and particulateswithout compromising wearer comfort by allowing breathability of air and water vapor to permeate the fabric.

[0258] In some embodiments, the article comprising a sheet of nonwoven flash-spun plexifilamentary fibrils is a chemical protective clothing. In some embodiments, the clothing as described herein may be used in various environments to protect the wearer from particulate hazards as well as acidic or basic aqueous liquid hazards which can be found in applications like chemical processing, pharmaceutical handling, paint applications, general maintenance, etc. In some embodiments, the clothing as described herein helps to protect the wearer against the hazard of a chemical permeating through the clothing during the time of use (resistance to chemical permeation). A basic solution such as sodium hydroxide (NaOH), when used as a cleaning agent, is an example of an aqueous liquid hazard. In addition, a wearer may experience closed space environments as well as different temperature and humidity conditions. In some embodiments, the clothing as described herein helps to provide a balanced level of durability (i.e., high abrasion resistance) combined with comfort (i.e. , low water vapor resistance and high softness I low handle-o-meter stiffness) and excellent barrier protection to liquids and particles. Furthermore, the clothing as described herein helps to provide excellent protection to penetration by blood and viruses, i.e., it has a good blood barrier according to ISO 16603 and a good viral barrier according to ISO 16604. Furthermore, low water vapor resistance (Ret) helps to provide appropriate comfort to the wearer in different climate conditions.

[0259] In some embodiments, the article comprising a sheet of nonwoven flash-spun plexifilamentary fibrils is a cover, selected from, but not limited to, protective covers, shoe covers, operating back-table covers, equipment covers for operating processes, equipment covers for biological and drug manufacturing processes, portable biohazard tents and enclosures, isolation fabrics, emergency shelters, mobile operating containment enclosures, or sterilization wraps, which helps to protect equipment or persons against harmful substances that may have an adverse effect, such as blood and viruses, i.e., it has a high blood barrier according to ISO 16603 and a high virus barrier according to ISO 16604.

[0260] In some embodiments, the sheet can be used for outdoor and sports apparel, including, but not limited to, jackets, windbreakers, pants, footwear and other camping and outdoor equipment. These applications often require lightweight, weather-resistant options with the breathability to maintain comfort through air permeability and sweat (water vapor) management.

[0261] In some embodiments, the sheet can be used for active packaging, including, but not limited to, desiccant pouches. Active packaging often requires high liquid and particle barriers with gas permeability, e.g., those that involve sensitive electronic equipment and sensors that require materials which are water-resistant, dustproof, and breathable.In some embodiments, the sheets may be used as car covers, soft cases, or bags. In some embodiments, the protective clothing comprises a bonded sheet of flash-spun plexifilamentary fibrils of polyethylene. In some embodiments, the protective clothing is a single-layer protective clothing comprising one or more bonded sheets of flash-spun plexifilamentary fibrils of polyethylene. In instances where the single-layer protective clothing comprises two or more bonded sheets of flash-spun plexifilamentary fibrils of polyethylene, the two or more bonded sheets are combined or attached adjacent to each other to form one single layer. In some embodiments, the protective clothing is a single-layer protective clothing comprising one or more bonded sheets of flash-spun plexifilamentary fibrils of polyethylene but not comprising sheets which are not bonded sheets of flash-spun plexifilamentary fibrils of polyethylene.

[0262] In some embodiments, the protective clothing is a full body coverall, a coat, a hat, pants, or gloves.

[0263] In some embodiments, the protective clothing comprises, consists essentially of, or consists of pieces of one or more bonded sheets of flash-spun plexifilamentary fibers, at least one stitched seam comprising a yarn, optionally at least one zipper, and optionally one or more elastic bands. At the seam, at least two pieces of bonded sheets are stitched together, and form a single-layer protective clothing. In some embodiments, the yarn of the stitched seam may include a hydrophobic yarn to improve the impermeability of stitched seams, as described in US 2013 / 0232675 A1. In some embodiments, the stitched seam may be covered with a protective tape at the outside of the clothing yarn to improve the impermeability of the stitched seams.

[0264] In some embodiments, the protective clothing comprises, consists essentially of, or consists of pieces of one or more bonded sheets of flash-spun plexifilamentary fibrils, at least one welded seam, optionally at least one zipper, and optionally one or more elastic bands. Welded seams may be ultrasonically welded or combined by other means using heat and pressure.

[0265] In some embodiments, the protective clothing comprises one or more elastic bands. In some embodiments, an elastic band may be present in the back of the protective clothing to provide comfort and fit. In some embodiments, elastic bands may be present at the end of the arms or legs of the protective clothing to provide a closer fit to the body of the wearer. In other embodiments, the protective garment may have a hood, which may include an elastic band, as described for example in US 9,155,922. The hood opening for a wearer’s face may have an elastic band, for example, to achieve an improved fit.

[0266] In some embodiments, the article comprises a bonded sheet of flash-spun plexifilamentary fibrils of polyethylene as defined herein, wherein the article has a basis weight from about 15 g / m2to about 54 g / m2, a Ret from about 2 m2Pa / W to about 10 m2Pa / W, and ablood barrier measured according to ISO 16603 of at least 1.75 kPa, or a viral barrier measured according to ISO 16604 of at least 0 kPa, or both.

[0267] In some embodiments, the article comprises a bonded sheet of flash-spun plexifilamentary fibrils of polyethylene, wherein the article has a basis weight from about 15 g / m2to about 54 g / m2, a Ret from about 2 m2Pa / Wto about 10 m2Pa / W, and a blood barrier measured according to ISO 16603 of at least 1.75 kPa, or a viral barrier measured according to ISO 16604 of at least 0 kPa, or both.

[0268] In some embodiments, the article has a basis weight from about 15 g / m2to about 54 g / m2, from about 30 g / m2to about 54 g / m2, from about 33 g / m2to about 48 g / m2, from about 39 g / m2to about 48 g / m2, from about 39 g / m2to about 43 g / m2, from about 33 g / m2to about 37 g / m2, from about 34 g / m2to about 40 g / m2, from about 43 g / m2to about 48 g / m2, or from about 48 g / m2to about 54 g / m2.

[0269] In some embodiments, the article has a Ret from about 2 m2Pa / W to about 10 m2Pa / W, from about 2 m2Pa / W to about 8 m2Pa / W, or from about 2 m2Pa / W to about 6 m2Pa / W. In other embodiments, the bonded sheet has a Ret from about 2 m2Pa / W to about 4 m2Pa / W, from about 4 m2Pa / W to about 6 m2Pa / W, or from about 3 m2Pa / W to about 5 m2Pa / W.

[0270] In some embodiments, the article has a blood barrier measured according to ISO 16603 of at least 1.75 kPa, at least 3.5 kPa, at least 7 kPa, at least 14 kPa, or at least 20 kPa.

[0271] In some embodiments, the article has a viral barrier measured according to ISO 16604 of at least 0 kPa, at least 1.75 kPa, at least 3.5 kPa, at least 7 kPa, at least 14 kPa, or of at least 20 kPa.

[0272] In some embodiments, the article has a blood barrier measured according to ISO 16603 of at least 1.75 kPa and a viral barrier measured according to ISO 16604 of at least 0 kPa. In other embodiments, the article has a blood barrier measured according to ISO 16603 of at least 3.5 kPa and a viral barrier measured according to ISO 16604 of at least 1.75 kPa or at least 3.5 kPa. In other embodiments, the article has a blood barrier measured according to ISO 16603 of at least 7 kPa and a viral barrier measured according to ISO 16604 of at least 1.75 kPa, at least 3.5 kPa, or at least 7 kPa. In other embodiments, the article has a blood barrier measured according to ISO 16603 of at least 14 kPa and a viral barrier measured according to ISO 16604 of at least 3.5 kPa, at least 7 kPa, or at least 14 kPa. In other embodiments, the article has a blood barrier measured according to ISO 16603 of at least 20 kPa and a viral barrier measured according to ISO 16604 of at least 7 kPa, at least 14 kPa, or at least 14 kPa.

[0273] In some embodiments, the article has a resistance to chemical permeation, BT-i.o, measured according to ISO 6529 against 10 wt% NaOH or 40 wt% NaOH of 60 min or above, of 120 min or above, of 240 min or above, or of 480 min or above, in other embodiments, the article has a resistance to chemical permeation, BTi.o, measured according to ISO 6529against 18 wt% H2SO4or 30 wt% H2SO4of 60 min or above, of 120 min or above, of 240 min or above, or of 480 min or above.

[0274] In some embodiments, the article has a resistance to chemical permeation, BT-i.o, measured according to ISO 6529 against 10 wt% NaOH or 40 wt% NaOH and against 18 wt% H2SO4or 30 wt% H2SO4of 60 min or above, of 120 min or above, of 240 min or above, or of 480 min or above.

[0275] In some embodiments, the article has a crock surface abrasion resistance from 10 to 50 cycles, in other embodiments, the article has a crock surface abrasion resistance from 20 to 50 cycles, or from 30 to 50 cycles, or from 40 to 50 cycles.

[0276] In some embodiments, the article has a Handle-O-Meter stiffness, normalized to basis weight, of about 1 mN / (g / m2) to about 30 mN / (g / m2), of about 1 mN / (g / m2) to about 20 mN / (g / m2), of about 2 mN / (g / m2) to about 10 mN / (g / m2), of about 2 mN / (g / m2) to about 5 mN / (g / m2), or of about 10 mN / (g / m2) to about 30 mN / (g / m2).

[0277] In some embodiments, the article has a basis weight from about 15 g / m2to about 54 g / m2, from about 30 g / m2to about 54 g / m2, from about 33 g / m2to about 48 g / m2, from about 39 g / m2to about 48 g / m2, from about 39 g / m2to about 43 g / m2, from about 33 g / m2to about 37 g / m2, from about 34 g / m2to about 40 g / m2, from about 43 g / m2to about 48 g / m2, or from about 48 g / m2to about 54 g / m2, a Ret from about 2 m2Pa / W to about 8 m2Pa / W, and a blood barrier measured according to ISO 16603 of at least 1.75 kPa, or a viral barrier measured according to ISO 16604 of at least 0 kPa, or both, or a blood barrier measured according to ISO 16603 of at least 3.5 kPa, or a viral barrier measured according to ISO 16604 of at least 1.75 kPa, or at least 3.5 kPa, or both.

[0278] In some embodiments, the article has a basis weight from about 15 g / m2to about 54 g / m2, from about 30 g / m2to about 54 g / m2, from about 33 g / m2to about 48 g / m2, from about 39 g / m2to about 48 g / m2, from about 39 g / m2to about 43 g / m2, from about 33 g / m2to about 37 g / m2, from about 34 g / m2to about 40 g / m2, from about 43 g / m2to about 48 g / m2, or from about 48 g / m2to about 54 g / m2, a Ret from about 2 m2Pa / W to about 8 m2Pa / W, and a blood barrier measured according to ISO 16603 of at least 7 kPa, or a viral barrier measured according to ISO 16604 of at least 1.75 kPa, at least 3.5 kPa, or at least 7 kPa, or both, or a blood barrier measured according to ISO 16603 of at least 14 kPa, or a viral barrier measured according to ISO 16604 of at least 3.5 kPa, at least 7 kPa, or at least 14 kPa, or both.

[0279] In some embodiments, the article has a basis weight from about 15 g / m2to about 54 g / m2, from about 30 g / m2to about 54 g / m2, from about 33 g / m2to about 48 g / m2, from about 39 g / m2to about 48 g / m2, from about 39 g / m2to about 43 g / m2, from about 33 g / m2to about 37 g / m2, from about 34 g / m2to about 40 g / m2, from about 43 g / m2to about 48 g / m2, or from about 48 g / m2to about 54 g / m2, a Ret from about 2 m2Pa / W to about 8 m2Pa / W, and a blood barrier measured according to ISO 16603 of at least 1.75 kPa, or a viral barrier measuredaccording to ISO 16604 of at least 0 kPa, or both, or a blood barrier measured according to ISO 16603 of at least 3.5 kPa, or a viral barrier measured according to ISO 16604 of at least 1.75 kPa, or at least 3.5 kPa, or both, and a resistance to chemical permeation, BT-i.o, measured according to ISO 6529 against 10 wt% NaOH or against 40 wt% NaOH of 60 min or above, of 120 min or above, of 240 min or above, or of 480 min or above, or a resistance to chemical permeation, BTi0, measured according to ISO 6529 against 18 wt% H2SO4 or 30 wt% H2SO4 of 60 min or above, of 120 min or above, of 240 min or above, or of 480 min or above.

[0280] In some embodiments, the article has a basis weight from about 15 g / m2to about 54 g / m2, from about 30 g / m2to about 54 g / m2, from about 33 g / m2to about 48 g / m2, from about 39 g / m2to about 48 g / m2, from about 39 g / m2to about 43 g / m2, from about 33 g / m2to about 37 g / m2, from about 34 g / m2to about 40 g / m2, from about 43 g / m2to about 48 g / m2, or from about 48 g / m2to about 54 g / m2, a Ret from about 2 m2Pa / W to about 8 m2Pa / W, and a blood barrier measured according to ISO 16603 of at least 7 kPa, or a viral barrier measured according to ISO 16604 of at least 1.75 kPa, at least 3.5 kPa, or at least 7 kPa, or both, or a blood barrier measured according to ISO 16603 of at least 14 kPa, or a viral barrier measured according to ISO 16604 of at least 3.5 kPa, at least 7 kPa, or at least 14 kPa, or both, and a resistance to chemical permeation, BT1 0, measured according to ISO 6529 against 10 wt% NaOH or against 40 wt% NaOH of 60 min or above, of 120 min or above, of 240 min or above, or of 480 min or above, or a resistance to chemical permeation, BT-i.o, measured according to ISO 6529 against 18 wt% H2SO4or 30 wt% H2SO4of 60 min or above, of 120 min or above, of 240 min or above, or of 480 min or above.

[0281] In some embodiments, the article has a basis weight from about 15 g / m2to about 54 g / m2, from about 30 g / m2to about 54 g / m2, from about 33 g / m2to about 48 g / m2, from about 39 g / m2to about 48 g / m2, from about 39 g / m2to about 43 g / m2, from about 33 g / m2to about 37 g / m2, from about 34 g / m2to about 40 g / m2, from about 43 g / m2to about 48 g / m2, or from about 48 g / m2to about 54 g / m2, a Ret from about 2 m2Pa / W to about 8 m2Pa / W, and a blood barrier measured according to ISO 16603 of at least 1.75 kPa, or a viral barrier measured according to ISO 16604 of at least 0 kPa, or both, or a blood barrier measured according to ISO 16603 of at least 3.5 kPa, or a viral barrier measured according to ISO 16604 of at least 1.75 kPa, or at least 3.5 kPa, or both, and a crock surface abrasion resistance from 10 to 50 cycles, or from 20 to 50 cycles, or from 30 to 50 cycles, or from 40 to 50 cycles.

[0282] In some embodiments, the article has a basis weight from about 15 g / m2to about 54 g / m2, from about 30 g / m2to about 54 g / m2, from about 33 g / m2to about 48 g / m2, from about 39 g / m2to about 48 g / m2, from about 39 g / m2to about 43 g / m2, from about 33 g / m2to about 37 g / m2, from about 34 g / m2to about 40 g / m2, from about 43 g / m2to about 48 g / m2, or from about 48 g / m2to about 54 g / m2, a Ret from about 2 m2Pa / W to about 8 m2Pa / W, and a bloodbarrier measured according to ISO 16603 of at least 7 kPa, or a viral barrier measured according to ISO 16604 of at least 1.75 kPa, at least 3.5 kPa, or at least 7 kPa, or both, or a blood barrier measured according to ISO 16603 of at least 14 kPa, or a viral barrier measured according to ISO 16604 of at least 3.5 kPa, at least 7 kPa, or at least 14 kPa, or both, and a crock surface abrasion resistance from 10 to 50 cycles, or from 20 to 50 cycles, or from 30 to 50 cycles, or from 40 to 50 cycles.

[0283] In some embodiments, the article has a basis weight from about 15 g / m2to about 54 g / m2, from about 30 g / m2to about 54 g / m2, from about 33 g / m2to about 48 g / m2, from about 39 g / m2to about 48 g / m2, from about 39 g / m2to about 43 g / m2, from about 33 g / m2to about 37 g / m2, from about 34 g / m2to about 40 g / m2, from about 43 g / m2to about 48 g / m2, or from about 48 g / m2to about 54 g / m2, a Ret from about 2 m2Pa / W to about 8 m2Pa / W, and a blood barrier measured according to ISO 16603 of at least 1.75 kPa, or a viral barrier measured according to ISO 16604 of at least 0 kPa, or both, or a blood barrier measured according to ISO 16603 of at least 3.5 kPa, or a viral barrier measured according to ISO 16604 of at least 1.75 kPa, or at least 3.5 kPa, or both, and a Handle-O-Meter stiffness, normalized to basis weight, of about 1 mN / (g / m2) to about 30 mN / (g / m2), of about 1 mN / (g / m2) to about 20 mN / (g / m2), of about 2 mN / (g / m2) to about 10 mN / (g / m2), of about 2 mN / (g / m2) to about 5 mN / (g / m2), or of about 10 mN / (g / m2) to about 30 mN / (g / m2).

[0284] In some embodiments, the article has a basis weight from about 15 g / m2to about 54 g / m2, from about 30 g / m2to about 54 g / m2, from about 33 g / m2to about 48 g / m2, from about 39 g / m2to about 48 g / m2, from about 39 g / m2to about 43 g / m2, from about 33 g / m2to about 37 g / m2, from about 34 g / m2to about 40 g / m2, from about 43 g / m2to about 48 g / m2, or from about 48 g / m2to about 54 g / m2, a Ret from about 2 m2Pa / W to about 8 m2Pa / W, and a blood barrier measured according to ISO 16603 of at least 7 kPa, or a viral barrier measured according to ISO 16604 of at least 1.75 kPa, at least 3.5 kPa, or at least 7 kPa, or both, or a blood barrier measured according to ISO 16603 of at least 14 kPa, or a viral barrier measured according to ISO 16604 of at least 3.5 kPa, at least 7 kPa, or at least 14 kPa, or both, and a Handle-O-Meter stiffness, normalized to basis weight, of about 1 mN / (g / m2) to about 30 mN / (g / m2), of about 1 mN / (g / m2) to about 20 mN / fg / m2), of about 2 mN / (g / m2) to about 10 mN / (g / m2), of about 2 mN / (g / m2) to about 5 mN / (g / m2), or of about 10 mN / (g / m2) to about 30 mN / (g / m2).

[0285] In some embodiments, the article has a basis weight from about 15 g / m2to about 54 g / m2, from about 30 g / m2to about 54 g / m2, from about 33 g / m2to about 48 g / m2, from about 39 g / m2to about 48 g / m2, from about 39 g / m2to about 43 g / m2, from about 33 g / m2to about 37 g / m2, from about 34 g / m2to about 40 g / m2, from about 43 g / m2to about 48 g / m2, or from about 48 g / m2to about 54 g / m2, a Ret from about 2 m2Pa / W to about 6 m2Pa / W, and a blood barrier measured according to ISO 16603 of at least 7 kPa, or a viral barrier measuredaccording to ISO 16604 of at least 1.75 kPa, at least 3.5 kPa, or at least 7 kPa, or both, or a blood barrier measured according to ISO 16603 of at least 14 kPa, or a viral barrier measured according to ISO 16604 of at least 3.5 kPa, at least 7 kPa, or at least 14 kPa, or both, or a blood barrier measured according to ISO 16603 of at least 20 kPa, or a viral barrier measured according to ISO 16604 of at least 7 kPa, at least 14 kPa, or at least 20 kPa, or both.

[0286] In some embodiments, the article has a basis weight from about 15 g / m2to about 54 g / m2, from about 30 g / m2to about 54 g / m2, from about 33 g / m2to about 48 g / m2, from about 39 g / m2to about 48 g / m2, from about 39 g / m2to about 43 g / m2, from about 33 g / m2to about 37 g / m2, from about 34 g / m2to about 40 g / m2, from about 43 g / m2to about 48 g / m2, or from about 48 g / m2to about 54 g / m2, a Ret from about 2 m2Pa / W to about 6 m2Pa / W, and a blood barrier measured according to ISO 16603 of at least 7 kPa, or a viral barrier measured according to ISO 16604 of at least 1.75 kPa, at least 3.5 kPa, or at least 7 kPa, or both, or a blood barrier measured according to ISO 16603 of at least 14 kPa, or a viral barrier measured according to ISO 16604 of at least 3.5 kPa, at least 7 kPa, or at least 14 kPa, or both, or a blood barrier measured according to ISO 16603 of at least 20 kPa, or a viral barrier measured according to ISO 16604 of at least 7 kPa, at least 14 kPa, or at least 20 kPa, or both, and a resistance to chemical permeation, BT1 0, measured according to ISO 6529 against 10 wt% NaOH or against 40 wt% NaOH of 60 min or above, of 120 min or above, of 240 min or above, or of 480 min or above, or a resistance to chemical permeation, BTij0, measured according to ISO 6529 against 18 wt% H2SO4or 30 wt% H2SO4of 60 min or above, of 120 min or above, of 240 min or above, or of 480 min or above.

[0287] In some embodiments, the article has a basis weight from about 15 g / m2to about 54 g / m2, from about 30 g / m2to about 54 g / m2, from about 33 g / m2to about 48 g / m2, from about 39 g / m2to about 48 g / m2, from about 39 g / m2to about 43 g / m2, from about 33 g / m2to about 37 g / m2, from about 34 g / m2to about 40 g / m2, from about 43 g / m2to about 48 g / m2, or from about 48 g / m2to about 54 g / m2, a Ret from about 2 m2Pa / W to about 6 m2Pa / W, and a blood barrier measured according to ISO 16603 of at least 7 kPa, or a viral barrier measured according to ISO 16604 of at least 1.75 kPa, at least 3.5 kPa, or at least 7 kPa, or both, or a blood barrier measured according to ISO 16603 of at least 14 kPa, or a viral barrier measured according to ISO 16604 of at least 3.5 kPa, at least 7 kPa, or at least 14 kPa, or both, or a blood barrier measured according to ISO 16603 of at least 20 kPa, or a viral barrier measured according to ISO 16604 of at least 7 kPa, at least 14 kPa, or at least 20 kPa, or both, and a crock surface abrasion resistance from 10 to 50 cycles, or from 20 to 50 cycles, or from 30 to 50 cycles, or from 40 to 50 cycles.

[0288] In some embodiments, the article has a basis weight from about 15 g / m2to about 54 g / m2, from about 30 g / m2to about 54 g / m2, from about 33 g / m2to about 48 g / m2, from about 39 g / m2to about 48 g / m2, from about 39 g / m2to about 43 g / m2, from about 33 g / m2to about37 g / m2, from about 34 g / m2to about 40 g / m2, from about 43 g / m2to about 48 g / m2, or from about 48 g / m2to about 54 g / m2, a Ret from about 2 m2Pa / W to about 6 m2Pa / W, and a blood barrier measured according to ISO 16603 of at least 7 kPa, or a viral barrier measured according to ISO 16604 of at least 1.75 kPa, at least 3.5 kPa, or at least 7 kPa, or both, or a blood barrier measured according to ISO 16603 of at least 14 kPa, or a viral barrier measured according to ISO 16604 of at least 3.5 kPa, at least 7 kPa, or at least 14 kPa, or both, or a blood barrier measured according to ISO 16603 of at least 20 kPa, or a viral barrier measured according to ISO 16604 of at least 7 kPa, at least 14 kPa, or at least 20 kPa, or both, and a Handle-O-Meter stiffness, normalized to basis weight, of about 1 mN / (g / m2) to about 30 mN / (g / m2), of about 1 mN / (g / m2) to about 20 mN / (g / m2), of about 2 mN / (g / m2) to about 10 mN / (g / m2), of about 2 mN / (g / m2) to about 5 mN / (g / m2), or of about 10 mN / (g / m2) to about 30 mN / (g / m2).

[0289] In some embodiments, the article has a basis weight from about 48 g / m2to about 54 g / m2, a Ret from about 2 m2Pa / Wto about 6 m2Pa / W, and a blood barrier measured according to ISO 16603 of at least 20 kPa, or a viral barrier measured according to ISO 16604 of at least 7 kPa, at least 14 kPa, or at least 20 kPa, or both.

[0290] In some embodiments, the article has a basis weight from about 48 g / m2to about 54 g / m2, a Ret from about 2 m2Pa / W to about 6 m2Pa / W, and a blood barrier measured according to ISO 16603 of at least 20 kPa, or a viral barrier measured according to ISO 16604 of at least 7 kPa, at least 14 kPa, or at least 20 kPa, or both, and a resistance to chemical permeation, BT-i.o, measured according to ISO 6529 against 10 wt% NaOH or against 40 wt% NaOH of 60 min or above, of 120 min or above, of 240 min or above, or of 480 min or above, ora resistance to chemical permeation, BTi,0, measured according to ISO 6529 against 18 wt% H2SO4or 30 wt% H2SO4of 60 min or above, of 120 min or above, of 240 min or above, or of 480 min or above.

[0291] In some embodiments, the article has a basis weight from about 48 g / m2to about 54 g / m2, a Ret from about 2 m2Pa / W to about 6 m2Pa / W, and a blood barrier measured according to ISO 16603 of at least 20 kPa, or a viral barrier measured according to ISO 16604 of at least 7 kPa, at least 14 kPa, or at least 20 kPa, or both, and a crock surface abrasion resistance from 10 to 50 cycles, or from 20 to 50 cycles, or from 30 to 50 cycles, or from 40 to 50 cycles.

[0292] In some embodiments, the article has a basis weight from about 48 g / m2to about 54 g / m2, a Ret from about 2 m2Pa / W to about 6 m2Pa / W, and a blood barrier measured according to ISO 16603 of at least 20 kPa, or a viral barrier measured according to ISO 16604 of at least 7 kPa, at least 14 kPa, or at least 20 kPa, or both, and a Handle-O-Meter stiffness, normalized to basis weight, of about 1 mN / (g / m2) to about 30 mN / (g / m2), of about 1 mN / (g / m2) to about 20 mN / (g / m2), of about 2 mN / (g / m2) to about 10 mN / (g / m2), of about 2 mN / (g / m2) to about 5 mN / (g / m2), or of about 10 mN / (g / m2) to about 30 mN / (g / m2).Further embodiments relate to a multilayer structure comprising at least one sheet of nonwoven flash-spun plexifilamentary fibrils as described herein, and at least one further sheet or a film. In some embodiments, the multilayer structure may comprise flash-spun discontinuous, cut, staple, or pulped fibers, and at least one further sheet or film.

[0293] In some embodiments, the multilayer structure comprises a film that is a microporous film. In one embodiment, the microporous film is a film that is filled and stretched as described in US 9,809,004 B2. Microporous films from highly filled polymers, usually polyolefins, may be prepared by any methods known in the art. Typically, a combination of a polyolefin, usually a polyethylene, is compounded with a filler, usually calcium carbonate, and extruded and stretched into a film to form a microporous film. Suitable examples of microporous films include those described in US 4,472,328, US 4,350,655, and US 4,777,073. A multilayer structure comprising a microporous film and at least one sheet of nonwoven flash-spun plexifilamentary fibrils as described herein can be used in a variety of applications, including, but not limited to protective apparel.

[0294] In some embodiments, the multilayer structure is a laminated structure comprising a microporous film laminated with at least one sheet of nonwoven flash-spun plexifilamentary fibrils as described herein. In some embodiments, a microporous film and a sheet of nonwoven flash-spun plexifilamentary fibrils may be laminated using an adhesive layer situated in contact with a least a portion of both the microporous film and the sheet of nonwoven flash-spun plexifilamentary fibrils, as described in US 9,809,004 B2.

[0295] Further embodiments relate to use of the sheet of nonwoven flash-spun plexifilamentary fibrils as described herein for preparing a multilayer structure.

[0296] Further embodiments relate to an article comprising at least one sheet of nonwoven flash-spun plexifilamentary fibrils as described herein or comprising at least one multilayer structure as described herein. In some embodiments, the article is selected from protective clothing, outdoor and sports apparel, active packaging, covers for equipment including car covers, and cargo covers.

[0297] In some embodiments, the article can be used for protective clothing. Protective clothing includes, but is not limited to, industrial, military, and medical protective clothing applications. Many of these protective clothing applications often require barrier protection against liquids and particulates without compromising wearer comfort by allowing breathability of air and water vapor to permeate the fabric.

[0298] In some embodiments, the article can be used for outdoor and sports apparel, including, but not limited to, jackets, windbreakers, pants, footwear and other camping and outdoor equipment. These applications often require lightweight, weather-resistant options with the breathability to maintain comfort through air permeability and sweat (water vapor) management.In some embodiments, the article can be used for active packaging, including, but not limited to, desiccant pouches. Active packaging often requires high liquid and particle barriers with gas permeability, e.g., those that involve sensitive electronic equipment and sensors that require materials which are water-resistant, dustproof, and breathable.

[0299] In some embodiments, the article may be used as car covers, soft cases, or bags.

[0300] EXAMPLES

[0301] Different bonded sheets of nonwoven flash-spun plexifilamentary fibrils have been prepared. The experimental procedure and results are provided below. These examples are given to illustrate exemplary embodiments of the invention and should not be interpreted as limiting in any way.

[0302] Materials Used

[0303] N-pentane, CAS Nr 109-66-0, has an atmospheric boiling point of 36.1 °C and a molecular weight of 72.151 g / mol. The n-pentane used had a purity level above 95 percent by weight.

[0304] Cyclopentane, CAS Nr 287-92-3, has an atmospheric boiling point of 49.2 °C and a molecular weight of 70.13 g / mol. The cyclopentane used had purity level above 95 percent by weight.

[0305] Dichloromethane, CAS Nr. 75-09-2, has an atmospheric boiling of 39.6 °C and a molecular weight of 84.93 g / mol. The dichloromethane used had a purity level above 99.5 percent by weight.

[0306] 2H,3H-decafluoropentane (HFC-43-10mee), CAS Nr. 138495-42-8, has an atmospheric boiling point of 55 °C and a molecular weight of 252.05 g / mol. The 2H,3H-decafluoropentane used had a purity level above 99.5 percent by weight.

[0307] Three different polyethylenes were used:

[0308] Polyethylene A (PE A) was a polyethylene having a density of 0.955 g / cm3(ISO 1183), a melt flow rate of 0.7 g / 10min (ISO 1133, 190 °C / 2.16 kg), and a melt flow rate of 24.5 g / 10min (ISO 1133, 190 °C / 21.6 kg).

[0309] Polyethylene B (PE B) was a polyethylene having a density of 0.960 g / cm3(ISO 1183), a melt flow rate of 1.2 g / 10min (ISO 1133, 190 °C / 2.16 kg), and a melt flow rate of 30 g / 10min (ISO 1133, 190 °C / 21.6 kg).Polyethylene C (PE C) was a linear low-density polyethylene-co-hexene copolymer having a density of 0.934 g / cm3(ISO 1183), a melt flow rate of 0.9 g / 10min (ISO 1133, 190 °C / 2.16 kg), and a melt flow rate of 30 g / 10min (ISO 1133, 190 °C / 21.6 kg).

[0310] Results

[0311] Comparative Example CE A and Examples 1 to 7

[0312] Flash-spun sheets were produced using the flash spinning process described by US 3,227,794, and US 3,851 ,023 at a spin temperature of 202 °C, using a spin fluid of 12 wt% polymer in a hydrocarbon-based spin agent that was a mixture of n-pentane and cyclopentane (herein also referred to as “H”). The nominal basis weight of the sheets was 48 g / m2.

[0313] Comparative example CE A and Examples 1 to 7 were treated with a warm compression pre-bonding step before thermally bonding.

[0314] The consolidated flash-spun sheets were subjected to a warm compression prebonding step, as described in the following and using the conditions indicated in Table 1 below.

[0315] A heated platen press was used to perform warm compression pre-bonding on each of the flash-spun sheets. The top platen comprised (in order from top to bottom): a 4” thick steel backing plate suspended from the crosshead, a 1 ” thick layer of high temperature thermal insulation, and a 15” x 15” square, 1.25” thick copper plate heated by means of embedded rod heaters mounted with thermal grease. The lower surface of the copper plate was the surface which contacted the upper surface of the sample when the platen press was closed. The bottom platen comprised an identical 15” x 15” square, 1.25” thick copper plate heated in the same way, a 1 ” thick layer of high temperature thermal insulation, and a 4” thick steel backing plate bolted to the table on which the platen press was mounted. The upper surface of the copper plate additionally had a 1 / 8” thick sheet of Viton® rubber attached to it to better distribute the pressure over the 15” x 15” platen, and this was the surface which contacted the lower surface of the sample when the platen press was closed. At any temperature setting from 80 °C to 150 °C, the temperature distribution over the surface of the 15” x 15” platens repeatably varied by no more than ±0.5 °C with the platen press closed.

[0316] The top heated platen was mounted to the crosshead with a fixture that allowed the top platen to self-align on the bottom platen through a loading ball, but without allowing any rotation of the top platen in the x-y plane. This provided uniform pressure applied over the 15” x 15” square surface of the platen.

[0317] To minimize shrinkage and distortion of the flash-spun sheets during processing, each sheet was clamped along its edges to a 30” x 24” rigid metal frame having a 17” x 17” square window cut out. With the platen press open, the metal frame with the flash-spun sheet clamped thereto was slid on metal rails into the platen press. The flash-spun sheet was positioned at aheight of approximately %-inch (6.35 mm) above the bottom platen of the platen press. The platen press was then closed by means of a hydraulically actuated crosshead to apply a specified pressure to the flash-spun sheet for a specified time. The load was ramped to the target pressure at a rate of 20,000 Ibf / s (89 kN / s) The target pressure was then held for 1 second before opening the platen press. After opening the platen press, the metal frame holding the compressed sheet was withdrawn from the platen press along the rails, the restraining clamps were opened, and the compressed sheet was removed and allowed to cool to room temperature.

[0318] Subsequently, each of the compressed sheets was subjected to a thermal bonding step, using the conditions indicated in Table 1 below. For the thermal bonding step, the same heated platen press as for the warm compression pre-bonding step was used. The top heated platen was mounted to the crosshead with a slide fixture that allowed the top platen to apply only its own dead weight load to the sample. This corresponded to a pressure of about 0.1 bar. The slide fixture did not allow any top platen rotation in the x-y plane. The heated bonding step pressure was held for 2 seconds.

[0319] The thermal bonding temperature for Comparative example CE A was less than the Melting Extrapolated Onset Temperature (Teim), meaning that it was not heated sufficiently to melt the fibrils.

[0320] The spinning, warm compression pre-bonding, and thermal bonding conditions and sheet properties are reported in Table 1, below.

[0321] Table 1: Summary of the sheet preparation of Comparative Examples CE A and Examples 1 to 7.

[0322] >

[0323]

[0324]

[0325] *1) Teim is the Melting Extrapolated Onset Temperature, *2) Tmis the melting point

[0326] Comparative Examples CE A illustrates that the warm compression pre-bonding step must be combined with a thermal bonding step in a temperature range sufficient to melt the fibrils and create a bonded sheet. According to the teaching provided in US 3,442,740, at least one surface of the sheet should reach a temperature within Tmand Tm- 7 °C to thermally bond. At temperatures below Tm- 7 °C, the sheet does not thermally bond. Without a thermal bonding step following the warm compression pre-bonding, the fibril network does not fuse and the sheet can be deflected and deformed under hydrostatic pressure and the liquid barrier decreases.

[0327] Examples 1 to 7 illustrate that for a warm compression pre-bonded and thermally bonded sheet, hydrostatic head and WVTR increase, a very low particle penetration is maintained, and sufficient air permeability is achieved. Different combinations of temperature and pressure for warm compression pre-bonding yield different property balances. Therefore, the property balances necessary to meet the requirements of different applications can be easily accomplished.

[0328] Comparative Examples CE B and CE C and Examples 8 and 9

[0329] Flash-spun sheets were produced using the flash spinning process described for Comparative Examples CE A and Examples 1 to 7.

[0330] Comparative example CE B was not treated with a warm compression pre-bonding step before thermally bonding. Comparative example CE C and examples 8 and 9 were treated with a warm compression pre-bonding step before thermally bonding. The warm compression pre-bonding and thermal bonding steps were performed as described in CE A and E1-7. Comparative example CE C was produced using the same process conditions as reported in Table 1 for CE A. Example 8 was produced using the same process conditions as reported in Table 1 for E4. Example 9 was produced using the same process conditions as reported in Table 1 for E5.The flash-spun sheets were subjected to a warm compression pre-bonding step followed by a thermal bonding step, or a thermal bonding step only as described above using the conditions indicated in Table 2 below.

[0331] The spinning, warm compression pre-bonding, and thermal bonding conditions and sheet properties are reported in Table 2, below.

[0332] Table 2: Summary of the sheet preparation of Comparative Examples CE B and CE C and Examples E8 to E9.

[0333] >

[0334]

[0335] *1) Teim is the Melting Extrapolated Onset Temperature, *2) Tmis the melting point

[0336] Comparative Example CE B illustrates that thermal bonding without warm compression can create a soft structure bonded sheet. However, compared to E1-9, further property improvements can be made by combining thermal bonding with warm compression pre-bonding. Namely, an increase in liquid barrier for similar or better gas permeability and particle barrier, and an improvement in softness can be achieved.

[0337] Comparative Example CE C illustrates that without a thermal bonding step following warm compression pre-bonding, the sheet remains soft and with good air permeability, but hydrostatic head is low.Examples 8 and 9 illustrate that for a warm compression pre-bonded and thermally bonded sheet, the softness and flux-barrier balance can be further improved over a process without the combination of warm compression pre-bonding and thermal bonding. Compared to CE B and CE C, the liquid barrier of the sheets in E8 and E9 is about 60-90% higher, and with a similar or better sheet softness.

[0338] Comparative Examples CE D and CE E and Examples 10 to 12

[0339] Flash-spun sheets were produced using the flash spinning process described by US 3,227,794 and US 3,851,023 at a nominal spin temperature of 195 °C, using a spin fluid of 12 wt% or 16 wt% polymer blends in a hydrocarbon-based spin agent that was a mixture of n-pentane and cyclopentane (herein also referred to as “H”). The nominal basis weight of the sheet was 45 or 42 g / m2.

[0340] Comparative example CE D was treated with a preheating step before thermally bonding. Examples E10 to E12 were treated with a warm compression pre-bonding step before thermally bonding. The warm compression pre-bonding and thermal bonding steps were performed as described in CE A and E1-7 in which the sheet is cooled between the steps.

[0341] Comparative example CE E was treated with a preheating step followed by thermally bonding, according to the teaching provided in US 5,972,147. During the preheating step, the sheet was restrained and heated with no applied compressive pressure. The preheating step was directly followed by thermal bonding without cooling the sheet between steps. The heated platen press described in CE A was used with a modified process described below.

[0342] With the platen press open, the metal frame with the flash-spun sheet clamped thereto, was slid on metal rails into the platen press. The flash-spun sheet was positioned at a height of approximately -inch (6.35 mm) above the bottom platen of the platen press. The platen press was then lowered into contact with the top surface of the flash-spun sheet by means of a hydraulically actuated crosshead and then held in contact for 1 second without applying compressive pressure. The bottom surface of the flash-spun sheet was radiatively heated by the bottom platen to a temperature within about 5 °C of that of the top platen. After the 1 second pre-heat, the platens were closed and the load was ramped to the target pressure at a rate of 20,000 Ibf / s (89 kN / s). The target pressure was then held for 2 seconds before opening the platen press. After opening the platen press, the metal frame holding the compressed sheet was withdrawn from the platen press along the rails, the restraining clamps were opened, and the compressed sheet was removed and allowed to cool to room temperature.The flash-spun sheets were subjected to a preheating or warm compression prebonding step followed by a thermal bonding step as described above using the conditions indicated in Table 3 below.

[0343] The spinning, warm compression pre-bonding, and thermal bonding conditions and sheet properties are reported in Table 3, below.

[0344] Table 3: Summary of the sheet preparation of Comparative Examples CE D and CE E and Examples E10 to E12.

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[0346] >

[0347]

[0348]

[0349] Comparative Examples CE D and CE E illustrate that a preheating step at low or no pressure followed by a thermal bonding step either directly or in a separate step resulted in a sheet with a poorer property balance than a warm compression pre-bonded and thermally bonded sheet. The sheet produced in CE D was stiffer with a lower hydrostatic head, withoutsignificantly improving WVTR. The sheet produced in CE E had a similar hydrostatic head to Examples 10 and 12, but the air and vapor permeability were significantly reduced.

[0350] Examples 10 to 12 illustrate that for a warm compression pre-bonded and thermally bonded sheet with blends of different polyethylene homopolymers and copolymers, the hydrostatic head and softness can be significantly improved for a similar WVTR, and with sufficient air permeability and particle penetration. Warm compression pre-bonding, when followed by thermal bonding, can significantly improve liquid barrier while maintaining similar gas permeability. Additional combinations of temperature and pressure within the temperature and pressure range of warm compression pre-bonding will allow further tuning of the property balance.

[0351] Comparative Examples CE F, CE G, CE H, and CE I, and Examples 13 and 16

[0352] Flash-spun sheets were produced using the flash spinning process described by US 3,227,794 and US 3,851,023 at different spin temperatures, using a spin fluid of 10 wt% polymer, 14 wt% polymer blends, or 16 wt% polymer blends in a hydrocarbon-based spin agent that was a mixture of n-pentane and cyclopentane (herein also referred to as “H”). The nominal basis weight of the sheet was 65, 53 or 35 g / m2.

[0353] Comparative examples CE F and CE H were treated with a cold compression step, where the sheet was subjected to compression at two different pressures without adding heat before thermally bonding, as described in US 4,247,318. Comparative example CE G was treated with a preheating step before thermally bonding with the process described for CE E, where the sheet was not cooled between steps. Comparative example CE I was not treated with a warm compression pre-bonding step before thermally bonding as described in CE B. Examples 13 to 16 were treated with a warm compression pre-bonding step before thermally bonding. The cold compression or warm compression pre-bonding and thermal bonding steps were performed as described in CE A and E1-7.

[0354] The flash-spun sheets were subjected to no pre-bonding step, a cold compression step, a preheating step, or a warm compression pre-bonding step followed by a thermal bonding step as described above using the conditions indicated in Table 4 below.

[0355] The spinning, warm compression pre-bonding, and thermal bonding conditions and sheet properties are reported in Table 4, below.

[0356] Table 4: Summary of the sheet preparation of Comparative Examples CE F, CE G, CE H, and CE I, and Examples 13 to 16.

[0357] | Example | CE F | CE G | CE H | CE I | E13 | E14 | E15 | E16 |

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[0359] > >

[0360]

[0361] *1) Blend 1 is a blend of Polyethylene A / Polyethylene B at a weight ratio of 60 / 40

[0362] *2) Teimis the Melting Extrapolated Onset Temperature,

[0363] *3) Tmis the melting point

[0364] Comparative examples CE F and CE H illustrate that a cold compression step, or compressing without adding heat, followed by thermal bonding, results in no significant improvement in the property balance compared to CE I, which was subjected to thermal bonding only. Softness, hydrostatic head, and gas permeability were similar with and without cold compression. For cold compressed and thermally bonded sheets of basis weights of about 35 g / m2and about 53 g / m2, the hydrostatic head is outside the ranges claimed in this invention.

[0365] Comparative example CE G illustrates that to achieve a high hydrostatic head and WVTR from a preheating step prior to thermal bonding, there is a significant trade-off of a large reduction in air permeability. Compared to a warm compression pre-bonded and thermally bonded sheet of a similar basis weight, hydrostatic head, and WVTR, the sheet ofCE G has about a 600% increase in Gurley Hill, meaning the sheet is significantly less breathable. For applications such as medical breathable protective clothing, where the comfort of the wearer is important to the function of the garment, a decrease in air permeability for the same liquid barrier protection is not preferred.

[0366] Comparative Example CE I illustrates that thermal bonding without warm compression pre-bonding can create a soft structure bonded sheet with good WVTR and air permeability. However, the hydrostatic head is insufficient for the demands of the applications herein.

[0367] Comparative examples CE F, CE G, CE H, and CE I illustrate a typical trade-off of liquid barrier and air permeability observed for flash-spun sheet with traditional thermal bonding approaches where the Gurley Hill porosity increases by about one or more orders of magnitude to achieve about twice the hydrostatic head.

[0368] Examples 13 to 16 illustrate that for a warm compression pre-bonded and thermally bonded sheet comprised of polyethylene homopolymers, the hydrostatic head and gas permeability balance, as well as the softness, can be significantly improved compared to thermally bonded sheets with cold compression, pre-heating, or no pre-bonding. Treating the sheet with a warm compression pre-bonding step before thermally bonding leads to large barrier improvements, even for low basis weight sheets of about 35 g / m2, where hydrostatic head is typically too low to meet product demands. A lightweight garment made from a low basis weight sheet, such as E16, can provide the wearer additional comfort, as it is softer and allows for greater gas permeability than higher basis weight garments. As the sheet basis weight increased, further improvements in liquid and particle barrier can be achieved, although the sheet also becomes stiffer.

[0369] The comparative examples in Table 4 illustrate many different approaches to prebonding which are known in the prior art. None of these approaches produce a sheet with the preferred flux-barrier property balance which is achieved with a warm compression prebonding and thermal bonding approach. Additional combinations of temperature and pressure within the temperature and pressure range of warm compression pre-bonding will allow further tuning of the property balance.

[0370] Comparative Examples CE J, CE K, and CE L and Examples 17 to 20.

[0371] Flash-spun sheets were produced using the flash spinning process described by US 3,227,794, and US 3,851 ,023 at a spin temperature of 210 °C, using a spin fluid of 10 wt% or 10.5 wt% polymer in a spin agent that was a mixture of dichloromethane and 2H,3H-decafluoropentane (herein also referred to as “D”). The nominal basis weight of the sheets was 42, 65, 73, or 105 g / m2.Comparative example CE J was not treated with a warm compression pre-bonding step before thermally bonding as described in CE B. Comparative example CE K was treated with a preheating step before thermally bonding with the process described for CE E, where the sheet was not cooled between steps. Comparative example CE L was treated with a cold compression step, where the sheet was subjected to compression without adding heat before thermally bonding. Examples 17 to 20 were treated with a warm compression pre-bonding step before thermally bonding. The cold compression or warm compression pre-bonding and thermal bonding steps were performed as described in CE A and E1-7.

[0372] The conditions for the cold compression step, the preheating step, the warm compression pre-bonding step, and the thermal bonding step are indicated in Table 5 below.

[0373] Table 5: Summary of the sheet preparation of Comparative Examples CE J, CE K, and CE L and Examples 17 to 20.

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[0375]

[0376] *1) Teim is the Melting Extrapolated Onset Temperature, *2) Tmis the melting pointExamples 17 to 20 illustrate that a beneficial combination of properties can be obtained using warm compression pre-bonding and thermal bonding of a spun sheet produced using a chlorine-based spin agent. As described in the examples above, for sheets produced using a hydrocarbon-based spin agent, the unique combination of heating and compressing at a temperature below the onset of melting of the polymer, then thermally bonding, results in a bonded sheet with an improved flux-barrier balance, which may also be softer and with higher lamination strength.

[0377] Examples 18 to 20 are spun at a higher basis weight compared to Example 17. Increasing basis weight generally results in higher liquid and particle barrier but presents a trade-off in gas permeability and softness. A similar trend was observed for sheets produced from a hydrocarbon spin agent of a comparable basis weight. The properties of Example 18, produced at a basis weight of about 65 g / m2, can be compared to Examples 13 and 14.

[0378] Comparative example CE L illustrates that cold compression, or compression without adding heat, followed by thermal bonding results in no significant improvement in the property balance compared to CE J, which was subjected to thermal bonding only. This trend was also observed for CE H and CE I, which were produced using a hydrocarbon-based spin agent.

[0379] Comparative example CE K illustrates that a preheating step with no compression, followed by thermal bonding, may produce a soft sheet with high hydrostatic head, but with a trade-off of an order of magnitude reduction in air permeability compared to Example 17, which has been subjected to a warm compression pre-bonding step followed by thermal bonding. A similar result was observed for CE G, which was produced using a hydrocarbon-based spin agent.

[0380] Treating the sheet with a warm compression pre-bonding step before thermally bonding is an effective method to produce large barrier improvements for a similar flux. Different combinations of temperature and pressure for warm compression pre-bonding can further tune the property balance.

[0381] Article Example E21

[0382] An article made from the bonded flash-spun sheet of Example E5 was examined. The properties of the article are shown in Table 6 below.

[0383] Table 6: Summary of Article E21

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[0391]

[0392] * Results are reported as the maximum pressure at which all three specimens pass.

[0393] ** Results are reported as an average of 6 measurements, with 3 measurements per side.

[0394] The article has a good combination of breathability (Ret) and barrier against blood and viruses, combined with a good resistance to chemical permeation according to ISO 6529:2013 against both sodium hydroxide and sulphuric acid and good mechanical stability (abrasion resistance), making it suitable for use in protective clothing applications, particularly medical or chemical protective clothing applications, and as medical cover. Further, the combination of breathability and barrier to biological hazards and to chemicals while maintaining abrasion resistance, softness and drapability, makes the article ideal for many different healthcare applications, such as operating back-table covers, and equipment covers, isolation fabrics, emergency bio shelters or mobile operating room containments, protective apparel, gowns, drapes, and shoe covers.

[0395] OTHER EMBODIMENTS

[0396] 1. In some embodiments, the present application provides a thermally bonded sheet of nonwoven flash-spun plexifilamentary fibrils, the sheet having

[0397] (a) a basis weight from about 15 g / m2to about 120 g / m2,

[0398] (b) a Gurley Hill porosity of about 2 seconds or more,

[0399] (c) a hydrostatic head from about y cmH2O to about 3000 cmH2O, wherein y is (2 times the Gurley Hill porosity value) plus 180, and

[0400] (d) a particle penetration of about 7 % or less.

[0401] 2. The sheet of embodiment 1 having a hydrostatic head from about y cmH2O to about 3000 cmH2O, wherein y is (2 times the Gurley Hill porosity value) plus 195 or plus 205.3. The sheet of embodiment 1 or 2 having a basis weight from about 15 g / m2to about 85 g / m2, from about 15 g / m2to about 75 g / m2, from about 15 g / m2to about 63 g / m2, from about 15 g / m2to about 54 g / m2, or from about 15 g / m2to about 48 g / m2.

[0402] 4. The sheet of any of embodiments 1 to 3 having a basis weight from about 30 g / m2to about 85 g / m2, from about 48 g / m2to about 75 g / m2, from about 30 g / m2to about 63 g / m2, from about 30 g / m2to about 54 g / m2, from about 30 g / m2to about 48 g / m2, from about 30 g / m2to about 54 g / m2, from about 33 g / m2to about 48 g / m2, from about 39 g / m2to about 48 g / m2, from about 39 g / m2to about 43 g / m2, from about 33 g / m2to about 37 g / m2, from about 34 g / m2to about 40 g / m2, from about 43 g / m2to about 48 g / m2, or from about 48 g / m2to about 54 g / m2.

[0403] 5. The sheet of embodiment 1 or 2 having a basis weight from about 63 g / m2to about 120 g / m2, from about 63 g / m2to about 85 g / m2, or from about 63 g / m2to about 75 g / m2. 6. The sheet of any of embodiments 1 to 5 having a Gurley Hill porosity from about 2 seconds to about 15 seconds, from about 2 seconds to about 10 seconds, from about 2 seconds to about 6 seconds, from about 6 seconds to about 20 seconds, or from about 10 seconds to about 20 seconds.

[0404] 7. The sheet of any of embodiments 1 to 6 having a particle penetration of about 5 % or less, of about 3 % or less, of about 1 % or less, or of about 0.1 % or less.

[0405] 8. The sheet of any of embodiments 1 to 6 having a particle penetration from about 0.01 % to about 7 %, from about 0.01 % to about 5 %, from about 0.01 % to about 3 %, or from about 0.01 % to about 1 %.

[0406] 9. The sheet of any of embodiments 1 to 8 having a hydrostatic head of about 3000 cmH2O or less, of about 1000 cmH2O or less, of about 800 cmH2O or less, of about 600 cmH2O or less, or of about 500 cmH2O or less.

[0407] 10. The sheet of any of embodiments 1 to 9 having a hydrostatic head from about y cmH2O to about 1000 cmH2O, wherein y is (2 times the Gurley Hill porosity value) plus 180, a hydrostatic head from about y cmH2O to about 1000 cmH2O, wherein y is (2 times the Gurley Hill porosity value) plus 195, or a hydrostatic head from about y cmH2O to about 1000 cmH2O, wherein y is (2 times the Gurley Hill porosity value) plus 205.

[0408] 11. The sheet of any of embodiments 1 to 9 having a hydrostatic head from about y cmH2O to about 600 cmH2O, wherein y is (2 times the Gurley Hill porosity value) plus 180, a hydrostatic head from about y cmH2O to about 600 cmH2O, wherein y is (2 times the Gurley Hill porosity value) plus 195, or a hydrostatic head from about y cmH2O to about 600 cmH2O, wherein y is (2 times the Gurley Hill porosity value) plus 205.

[0409] 12. The sheet of any of embodiments 1 to 11 having a WVTR from about 10,000 g / m2 / day to about 100,000 g / m2 / day, from about 10,000 g / m2 / day to about 80,000 g / m2 / day, from about10,000 g / m2 / day to about 60,000 g / m2 / day, or from about 10,000 g / m2 / day to about 40,000 g / m2 / day.

[0410] 13. The sheet of any of embodiments 1 to 12 having a WVTR from about 20,000 g / m2 / day to about 100,000 g / m2 / day, from about 20,000 g / m2 / day to about 80,000 g / m2 / day, from about 20,000 g / m2 / day to about 60,000 g / m2 / day, from about 40,000 g / m2 / day to about 100,000 g / m2 / day, from about 40,000 g / m2 / day to about 80,000 g / m2 / day, or from about 40,000 g / m2 / day to about 60,000 g / m2 / day.

[0411] 14. The sheet of any of embodiments 1 to 13 having a Handle-O-Meter stiffness from about 300 mN to about 2000 mN, from about 300 mN to about 1300 mN, from about 300 mN to about 1000 mN, or from about 300 mN to about 800 mN.

[0412] 15. The sheet of any of embodiments 1 to 13 having a Handle-O-Meter stiffness from about 2000 mN to about 8000 mN, from about 2000 mN to about 4000 mN, or from about 4000 mN to about 8000 mN.

[0413] 16. The sheet of any of embodiments 1 to 15 having a Handle-O-Meter stiffness, normalized to basis weight, from about 4 mN / (g / m2) to about 30 mN / (g / m2), from about 4 mN / (g / m2) to about 25 mN / (g / m2), or from about 4 mN / (g / m2) to about 20 mN / (g / m2).

[0414] 17. The sheet of any of embodiments 1 to 15 having a Handle-O-Meter stiffness, normalized to basis weight, from about 30 mN / (g / m2) to about 70 mN / (g / m2), from about 30 mN / (g / m2) to about 60 mN / (g / m2), or from about 30 mN / (g / m2) to about 50 mN / (g / m2).

[0415] 18. The sheet of any of embodiments 1 to 17, wherein the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene.

[0416] 19. The sheet of embodiment 18, wherein the polyethylene is high-density polyethylene (HDPE), or blends / mixtures of high-density polyethylene (HDPE) with low-density polyethylene (LDPE), or blends / mixtures of high-density polyethylene (HDPE) with linear low-density polyethylene (LLDPE).

[0417] 20. The sheet of any of embodiments 1 to 19 wherein the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 15 g / m2to about 120 g / m2, a Gurley Hill porosity of about 2 seconds or more, a hydrostatic head from about y cmH2O to about 3000 cmH2O, wherein y is (2 times the Gurley Hill porosity value) plus 180, and a particle penetration of about 7 % or less, of about 3 % or less, or of about 1 % or less.

[0418] 21. The sheet of any of embodiments 1 to 19 wherein the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 15 g / m2to about 120 g / m2, a Gurley Hill porosity of about 2 seconds or more, a hydrostatic head from about y cmH2O to about 3000 cmH2O, wherein y is (2 times the Gurley Hill porosity value) plus 195, and a particle penetration of about 1 % or less.22. The sheet of any of embodiments 1 to 19 wherein the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 15 g / m2to about 54 g / m2, a Gurley Hill porosity of about 2 seconds or more, a hydrostatic head from about y cmH2O to about 3000 cmH2O, wherein y is (2 times the Gurley Hill porosity value) plus 180, and a particle penetration of about 7 % or less, of about 3 % or less, or of about 1 % or less.

[0419] 23. The sheet of any of embodiments 1 to 19 wherein the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 30 g / m2to about 54 g / m2, a Gurley Hill porosity of about 2 seconds or more, a hydrostatic head from about y cmH2O to about 3000 cmH2O, wherein y is (2 times the Gurley Hill porosity value) plus 180, and a particle penetration of about 7 % or less, of about 3 % or less, or of about 1 % or less.

[0420] 24. The sheet of any of embodiments 1 to 19 wherein the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 15 g / m2to about 63 g / m2, a Gurley Hill porosity of about 2 seconds or more, a hydrostatic head from about y cmH2O to about 3000 cmH2O, wherein y is (2 times the Gurley Hill porosity value) plus 180, and a particle penetration of about 7 % or less, about 3 % or less, or about 1 % or less.

[0421] 25. The sheet of any of embodiments 1 to 19 wherein the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 30 g / m2to about 63 g / m2, a Gurley Hill porosity of about 2 seconds or more, a hydrostatic head from about y cmH2O to about 3000 cmH2O, wherein y is (2 times the Gurley Hill porosity value) plus 180, and a particle penetration of about 7 % or less, about 3 % or less, or about 1 % or less.

[0422] 26. The sheet of any of embodiments 1 to 19 wherein the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 15 g / m2to about 63 g / m2, a Gurley Hill porosity of about 2 seconds or more, a hydrostatic head from about y cmH2O to about 3000 cmH2O, wherein y is (2 times the Gurley Hill porosity value) plus 195, and a particle penetration of about 3 % or less or about 1 % or less.

[0423] 27. The sheet of any of embodiments 1 to 19 wherein the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 15 g / m2to about 63 g / m2, a Gurley Hill porosity of about 2 seconds or more, a hydrostatic head from about y cmH2O to about 3000 cmH2O, wherein y is (2 times the Gurley Hill porosity value) plus 180, a particle penetration of about 3 % or less or about 1 % or less, and a Handle-O-Meter stiffness, normalized to basis weight, of about 4 mN / (g / m2) to about 30 mN / (g / m2).28. The sheet of any of embodiments 1 to 19 wherein the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 15 g / m2to about 63 g / m2, a Gurley Hill porosity of about 2 seconds or more, a hydrostatic head from about y cmH2O to about 3000 cmH2O, wherein y is (2 times the Gurley Hill porosity value) plus 180, a particle penetration of about 3 % or less or about 1 % or less, and a water vapor transmission rate (WVTR) from about 10,000 g / m2 / day to about 100,000 g / m2 / day.

[0424] 29. The sheet of any of embodiments 1 to 19 wherein the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 15 g / m2to about 63 g / m2, a Gurley Hill porosity of about 2 seconds or more, a hydrostatic head from about y cmH2O to about 3000 cmH2O, wherein y is (2 times the Gurley Hill porosity value) plus 180, a particle penetration of about 3 % or less or about 1 % or less, a Handle-O-Meter stiffness, normalized to basis weight, of about 4 mN / (g / m2) to about 30 mN / (g / m2), and a water vapor transmission rate (WVTR) from about 10,000 g / m2 / day to about 100,000 g / m2 / day.

[0425] 30. The sheet of any of embodiments 1 to 19 wherein the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 30 g / m2to about 63 g / m2or from about 30 g / m2to about 54 g / m2, a Gurley Hill porosity of about 2 seconds or more, a hydrostatic head from about y cmH2O to about 3000 cmH2O, wherein y is (2 times the Gurley Hill porosity value) plus 180, and a particle penetration of about 1 % or less.

[0426] 31. The sheet of any of embodiments 1 to 19 wherein the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 63 g / m2to about 120 g / m2, a Gurley Hill porosity of about 2 seconds or more, a hydrostatic head from about y cmH2O to about 3000 cmH2O, wherein y is (2 times the Gurley Hill porosity value) plus 180, and a particle penetration of about 7 % or less, or of about 3 % or less or about 1 % or less.

[0427] 32. The sheet of any of embodiments 1 to 19 wherein the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 63 g / m2to about 120 g / m2, a Gurley Hill porosity of about 2 seconds or more, a hydrostatic head from about y cmH2O to about 3000 cmH2O, wherein y is (2 times the Gurley Hill porosity value) plus 180, a particle penetration of about 7 % or less, and a Handle-O-Meter stiffness, normalized to basis weight, of about 30 mN / (g / m2) to about 70 mN / (g / m2).

[0428] 33. The sheet of any of embodiments 1 to 19 wherein the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 63 g / m2to about 120 g / m2, a Gurley Hill porosity of about 2 seconds or more, ahydrostatic head from about y cmH2O to about 3000 cmH2O, wherein y is (2 times the Gurley Hill porosity value) plus 195, and a particle penetration of about 7 % or less, or about 3 % or less, or about 1 % or less.

[0429] 34. The sheet of any of embodiments 1 to 19 wherein the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 63 g / m2to about 120 g / m2, a Gurley Hill porosity of about 2 seconds or more, a hydrostatic head from about y cmH2O to about 3000 cmH2O, wherein y is (2 times the Gurley Hill porosity value) plus 205, and a particle penetration of about 1 % or less.

[0430] 35. In some embodiments, the present application provides a thermally bonded sheet of nonwoven flash-spun plexifilamentary fibrils, the sheet having

[0431] (a) a basis weight from about 15 g / m2to about 120 g / m2,

[0432] (b) a Gurley Hill porosity of about 20 seconds or more,

[0433] (c) a hydrostatic head from about p cmH2O to about 3000 cmH2O, wherein p is (2 times the Gurley Hill porosity value) plus 140, and

[0434] (d) a particle penetration of about 7 % or less.

[0435] 36. The sheet of embodiment 35 having a hydrostatic head from about p cmH20 to about 3000 cmH2O, wherein p is (2 times the Gurley Hill porosity value) plus 155, plus 180, plus 195, or plus 205.

[0436] 37. The sheet of embodiment 35 or 36 having a basis weight from about 15 g / m2to about 85 g / m2, from about 15 g / m2to about 75 g / m2, from about 15 g / m2to about 63 g / m2, from about 15 g / m2to about 54 g / m2, or from about 15 g / m2to about 48 g / m2.

[0437] 38. The sheet of any of embodiments 35 to 37 having a basis weight from about 30 g / m2to about 85 g / m2, from about 48 g / m2to about 75 g / m2, from about 30 g / m2to about 63 g / m2, from about 30 g / m2to about 54 g / m2, or from about 30 g / m2to about 48 g / m2.

[0438] 39. The sheet of embodiment 35 or 36 having a basis weight from about 63 g / m2to about 120 g / m2, from about 63 g / m2to about 85 g / m2, or from about 63 g / m2to about 75 g / m2. 40. The sheet of any of embodiments 35 to 39 having a Gurley Hill porosity of about 80 seconds or less, or of about 40 seconds or less.

[0439] 41. The sheet of any of embodiments 35 to 40 having a Gurley Hill porosity from about 20 seconds to about 80 seconds, or from about 20 seconds to about 40 seconds.

[0440] 42. The sheet of any of embodiments 35 to 41 having a particle penetration of about 5 % or less, of about 3 % or less, of about 1 % or less, or of about 0.1 % or less.

[0441] 43. The sheet of any of embodiments 35 to 42 having a particle penetration from about 0.01 % to about 7 %, from about 0.01 % to about 5 %, from about 0.01 % to about 3 %, or from about 0.01 % to about 1 %.44. The sheet of any of embodiments 35 to 43 having a hydrostatic head of about 3000 cmH2O or less, of about 1000 cmH20 or less, of about 800 cmH20 or less, of about 600 cmH20 or less, or of about 500 cmH20 or less.

[0442] 45. The sheet of any of embodiments 35 to 44 having a hydrostatic head from about p cmH2O to about 1000 cmH20, wherein p is (2 times the Gurley Hill porosity value) plus 140, plus 155, plus 180, plus 195, or plus 205.

[0443] 46. The sheet of any of embodiments 35 to 45 having a hydrostatic head from about p cmH2O to about 600 cmH2O, wherein p is (2 times the Gurley Hill porosity value) plus 140, plus 155, plus 180, plus 195, or plus 205.

[0444] 47. The sheet of any of embodiments 35 to 46 having a WVTR from about 10,000 g / m2 / day to about 100,000 g / m2 / day, from about 10,000 g / m2 / day to about 80,000 g / m2 / day, from about 10,000 g / m2 / day to about 60,000 g / m2 / day, or from about 10,000 g / m2 / day to about 40,000 g / m2 / day.

[0445] 48. The sheet of any of embodiments 35 to 47 having a WVTR from about 20,000 g / m2 / day to about 100,000 g / m2 / day, from about 20,000 g / m2 / day to about 80,000 g / m2 / day, from about 20,000 g / m2 / day to about 60,000 g / m2 / day, from about 40,000 g / m2 / day to about 100,000 g / m2 / day, from about 40,000 g / m2 / day to about 80,000 g / m2 / day, or from about 40,000 g / m2 / day to about 60,000 g / m2 / day.

[0446] 49. The sheet of any of embodiments 35 to 48 having a Handle-O-Meter stiffness from about 300 mN to about 2000 mN, from about 300 mN to about 1300 mN, from about 300 mN to about 1000 mN, or from about 300 mN to about 800 mN.

[0447] 50. The sheet of any of embodiments 35 to 48 having a Handle-O-Meter stiffness from about 2000 mN to about 8000 mN, from about 2000 mN to about 4000 mN, or from about 4000 mN to about 8000 mN.

[0448] 51. The sheet of any of embodiments 35 to 50 having a Handle-O-Meter stiffness, normalized to basis weight, from about 4 mN / (g / m2) to about 30 mN / (g / m2), from about 4 mN / (g / m2) to about 25 mN / (g / m2), or from about 4 mN / (g / m2) to about 20 mN / (g / m2).

[0449] 52. The sheet of any of embodiments 35 to 50 having a Handle-O-Meter stiffness, normalized to basis weight, from about 30 mN / (g / m2) to about 70 mN / (g / m2), from about 30 mN / (g / m2) to about 60 mN / (g / m2), or from about 30 mN / (g / m2) to about 50 mN / (g / m2).

[0450] 53. The sheet of any of embodiments 35 to 52, wherein the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene.

[0451] 54. The sheet of embodiment 53, wherein the polyethylene is high-density polyethylene (HDPE), or blends / mixtures of high-density polyethylene (HDPE) with low-density polyethylene (LDPE), or blends / mixtures of high-density polyethylene (HDPE) with linear low-density polyethylene (LLDPE).55. The sheet of any of embodiments 35 to 54, wherein the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 15 g / m2to about 120 g / m2, a Gurley Hill porosity of about 20 seconds or more, a hydrostatic head from about p cmH2O to about 3000 cmH2O, wherein p is (2 times the Gurley Hill porosity value) plus 140, and a particle penetration of about 7 % or less, of about 3 % or less, or of about 1 % or less.

[0452] 56. The sheet of any of embodiments 35 to 54, wherein the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 15 g / m2to about 120 g / m2, a Gurley Hill porosity of about 20 seconds or more, a hydrostatic head from about p cmH2O to about 3000 cmH2O, wherein p is (2 times the Gurley Hill porosity value) plus 140, and a particle penetration of about 7 % or less, of about 3 % or less, or of about 1 % or less.

[0453] 57. The sheet of any of embodiments 35 to 54, wherein the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 15 g / m2to about 120 g / m2, a Gurley Hill porosity of about 20 seconds or more, a hydrostatic head from about p cmH2O to about 3000 cmH2O, wherein p is (2 times the Gurley Hill porosity value) plus 155, plus 175, or plus 195, and a particle penetration of about 1 % or less.

[0454] 58. The sheet of any of embodiments 35 to 54, wherein the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 30 g / m2to about 120 g / m2, a Gurley Hill porosity of about 20 seconds or more, a hydrostatic head from about p cmH2O to about 3000 cmH2O, wherein p is (2 times the Gurley Hill porosity value) plus 140, and a particle penetration of about 7 % or less, of about 3 % or less, or of about 1 % or less.

[0455] 59. The sheet of any of embodiments 35 to 54, wherein the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 30 g / m2to about 63 g / m2, a Gurley Hill porosity of about 20 seconds or more, a hydrostatic head from about p cmH2O to about 3000 cmH2O, wherein p is (2 times the Gurley Hill porosity value) plus 140, and a particle penetration of about 7 % or less, of about 3 % or less, or of about 1 % or less.

[0456] 60. The sheet of any of embodiments 35 to 54, wherein the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 30 g / m2to about 63 g / m2, a Gurley Hill porosity of about 20 seconds or more, a hydrostatic head from about p cmH2O to about 3000 cmH2O, wherein p is (2 times the Gurley Hill porosity value) plus 140, a particle penetration of about 7 % or less, of about 3 % or less, or of about 1 % or less, and a Handle-O-Meter stiffness, normalized to basis weight, of about 4 mN / (g / m2) to about 30 mN / (g / m2).61. The sheet of any of embodiments 35 to 54, wherein the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 30 g / m2to about 63 g / m2, a Gurley Hill porosity of about 20 seconds or more, a hydrostatic head from about p cmH2O to about 3000 cmH2O, wherein p is (2 times the Gurley Hill porosity value) plus 140, a particle penetration of about 7 % or less, of about 3 % or less, or of about 1 % or less, and a water vapor transmission rate (WVTR) from about 10,000 g / m2 / day to about 100,000 g / m2 / day.

[0457] 62. The sheet of any of embodiments 35 to 54, wherein the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 30 g / m2to about 63 g / m2, a Gurley Hill porosity of about 20 seconds or more, a hydrostatic head from about p cmH2O to about 3000 cmH2O, wherein p is (2 times the Gurley Hill porosity value) plus 140, a particle penetration of about 7 % or less, of about 3 % or less, or of about 1 % or less, a Handle-O-Meter stiffness, normalized to basis weight, of about 4 mN / (g / m2) to about 30 mN / (g / m2), and a water vapor transmission rate (WVTR) from about 10,000 g / m2 / day to about 100,000 g / m2 / day.

[0458] 63. The sheet of any of embodiments 35 to 54, wherein the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 63 g / m2to about 120 g / m2, a Gurley Hill porosity of about 20 seconds or more, a hydrostatic head from about p cmH2O to about 3000 cmH2O, wherein p is (2 times the Gurley Hill porosity value) plus 155, and a particle penetration of about 7 % or less, of about 3 % or less, or of about 1 % or less.

[0459] 64. The sheet of any of embodiments 35 to 54, wherein the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 63 g / m2to about 120 g / m2, a Gurley Hill porosity of about 20 seconds or more, a hydrostatic head from about p cmH2O to about 3000 cmH2O, wherein p is (2 times the Gurley Hill porosity value) plus 155, a particle penetration of about 7 % or less, of about 3 % or less, or of about 1 % or less, and, a Handle-O-Meter stiffness, normalized to basis weight, of about 30 mN / (g / m2) to about 70 mN / (g / m2).

[0460] 65. In some embodiments, the present application provides a thermally bonded sheet of nonwoven flash-spun plexifilamentary fibrils, the sheet having

[0461] (a) a basis weight from about 15 g / m2to about 48 g / m2,

[0462] (b) a Gurley Hill porosity of about 2 seconds to about 20 seconds,

[0463] (c) a hydrostatic head from about m cmH2O to about 3000 cmH2O, wherein m is (2 times the Gurley Hill porosity value) plus 140, and

[0464] (d) a particle penetration of about 7 % or less.66. The sheet of embodiment 66 having a hydrostatic head from about m cmH20 to about 3000 cmH2O, wherein m is (2 times the Gurley Hill porosity value) plus 155, plus 180, plus 195, or plus 205.

[0465] 67. The sheet of any of embodiments 65 to 66 having a basis weight from about 30 g / m2to about 48 g / m2.

[0466] 68. The sheet of any of embodiments 65 to 67 having a Gurley Hill porosity from about 2 seconds to about 15 seconds, from about 2 seconds to about 10 seconds, from about 2 seconds to about 6 seconds, from about 6 seconds to about 20 seconds, or from about 10 seconds to about 20 seconds.

[0467] 69. The sheet of any of embodiments 65 to 68 having a particle penetration of about 5 % or less, of about 3 % or less, of about 1 % or less, or of about 0.1 % or less.

[0468] 70. The sheet of any of embodiments 65 to 69 having a particle penetration from about 0.01 % to about 7 %, from about 0.01 % to about 5 %, from about 0.01 % to about 3 %, or from about 0.01 % to about 1 %.

[0469] 71. The sheet of any of embodiments 65 to 70 having a hydrostatic head of about 3000 cmH2O or less, of about 1000 cmH2O or less, of about 800 cmH2O or less, of about 600 cmH2O or less, or of about 500 cmH2O or less.

[0470] 12.. The sheet of any of embodiments 65 to 71 having a hydrostatic head from about m cmH2O to about 1000 cmH2O, wherein m is (2 times the Gurley Hill porosity value) plus 140, plus 155, plus 180, plus 195, or plus 205.

[0471] 73. The sheet of any of embodiments 65 to 72 having a hydrostatic head from about m cmH2O to about 600 cmH2O, wherein m is (2 times the Gurley Hill porosity value) plus 140, plus 155, plus 180, plus 195 or plus 205.

[0472] 74. The sheet of any of embodiments 65 to 73 having a WVTR from about 10,000 g / m2 / day to about 100,000 g / m2 / day, from about 10,000 g / m2 / day to about 80,000 g / m2 / day, from about 10,000 g / m2 / day to about 60,000 g / m2 / day, or from about 10,000 g / m2 / day to about 40,000 g / m2 / day.

[0473] 75. The sheet of any of embodiments 65 to 74 having a WVTR from about 20,000 g / m2 / day to about 100,000 g / m2 / day, from about 20,000 g / m2 / day to about 80,000 g / m2 / day, from about 20,000 g / m2 / day to about 60,000 g / m2 / day, from about 40,000 g / m2 / day to about 100,000 g / m2 / day, from about 40,000 g / m2 / day to about 80,000 g / m2 / day, or from about 40,000 g / m2 / day to about 60,000 g / m2 / day.

[0474] 76. The sheet of any of embodiments 65 to 75 having a Handle-O-Meter stiffness from about 300 mN to about 2000 mN, from about 300 mN to about 1300 mN, from about 300 mN to about 1000 mN, or from about 300 mN to about 800 mN.77. The sheet of any of embodiments 65 to 75 having a Handle-O-Meter stiffness from about 2000 mN to about 8000 mN, from about 2000 mN to about 4000 mN, or from about 4000 mN to about 8000 mN.

[0475] 78. The sheet of any of embodiments 65 to 77 having a Handle-O-Meter stiffness, normalized to basis weight, from about 4 mN / (g / m2) to about 30 mN / (g / m2), from about 4 mN / (g / m2) to about 25 mN / (g / m2), or from about 4 mN / (g / m2) to about 20 mN / (g / m2).

[0476] 79. The sheet of any of embodiments 65 to 77 having a Handle-O-Meter stiffness, normalized to basis weight, from about 30 mN / (g / m2) to about 70 mN / (g / m2), from about 30 mN / (g / m2) to about 60 mN / (g / m2), or from about 30 mN / (g / m2) to about 50 mN / (g / m2).

[0477] 80. The sheet of any of embodiments 65 to 79, wherein the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene.

[0478] 81. The sheet of embodiment 80, wherein the polyethylene is high-density polyethylene (HDPE), or blends / mixtures of high-density polyethylene (HDPE) with low-density polyethylene (LDPE), or blends / mixtures of high-density polyethylene (HDPE) with linear low-density polyethylene (LLDPE).

[0479] 82. The sheet of any of embodiments 65 to 81, wherein the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 15 g / m2to about 48 g / m2, a Gurley Hill porosity from about 2 to about 20 seconds, a hydrostatic head from about m cmH2O to about 3000 cmH20, wherein m is (2 times the Gurley Hill porosity value) plus 140, and a particle penetration of about 7 % or less, of about 3 % or less, or of about 1 % or less.

[0480] 83. The sheet of any of embodiments 65 to 81, wherein the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 30 g / m2to about 48 g / m2, a Gurley Hill porosity from about 2 to about 20 seconds, a hydrostatic head from about m cmH2O to about 3000 cmH20, wherein m is (2 times the Gurley Hill porosity value) plus 140, and a particle penetration of about 7 % or less, of about 3 % or less, or of about 1 % or less.

[0481] 84. The sheet of any of embodiments 65 to 81, wherein the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 15 g / m2to about 48 g / m2, a Gurley Hill porosity from about 2 to about 10 seconds, a hydrostatic head from about m cmH2O to about 3000 cmH20, wherein m is (2 times the Gurley Hill porosity value) plus 140, and a particle penetration of about 7 % or less, of about 3 % or less, or of about 1 % or less.

[0482] 85. The sheet of any of embodiments 65 to 81, wherein the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 30 g / m2to about 48 g / m2, a Gurley Hill porosity from about 2 to about 10 seconds, a hydrostatic head from about m cmH2O to about 3000 cmH20, wherein m is (2 times theGurley Hill porosity value) plus 140, and a particle penetration of about 7 % or less, of about 3 % or less, or of about 1 % or less.

[0483] 86. The sheet of any of embodiments 65 to 81, wherein the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 30 g / m2to about 48 g / m2, a Gurley Hill porosity from about 2 to about 20 seconds, a hydrostatic head from about m cmH2O to about 3000 cmH20, wherein m is (2 times the Gurley Hill porosity value) plus 155, and a particle penetration of about 7 % or less, of 3 % or less, or of about 1 % or less.

[0484] 87. The sheet of any of embodiments 65 to 81, wherein the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 30 g / m2to about 48 g / m2, a Gurley Hill porosity from about 2 to about 10 seconds, a hydrostatic head from about m cmH2O to about 3000 cmH2O, wherein m is (2 times the Gurley Hill porosity value) plus 155, and a particle penetration about 7 % or less of 3 % or less, or of about 1 % or less.

[0485] 88. The sheet of any of embodiments 65 to 81, wherein the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 15 g / m2to about 48 g / m2, a Gurley Hill porosity from about 2 to about 6 seconds, a hydrostatic head from about m cmH2O to about 3000 cmH20, wherein m is (2 times the Gurley Hill porosity value) plus 140, and a particle penetration of about 5 % or less, of about 3 % or less, or of about 1 % or less.

[0486] 89. The sheet of any of embodiments 65 to 81, wherein the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 30 g / m2to about 48 g / m2, a Gurley Hill porosity from about 2 to about 6 seconds, a hydrostatic head from about m cmH2O to about 3000 cmH20, wherein m is (2 times the Gurley Hill porosity value) plus 140, and a particle penetration of about 5 % or less, of about 3 % or less, or of about 1 % or less.

[0487] 90. The sheet of any of embodiments 65 to 81, wherein the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 15 g / m2to about 48 g / m2, a Gurley Hill porosity from about 2 to about 6 seconds, a hydrostatic head from about m cmH2O to about 3000 cmH20, wherein m is (2 times the Gurley Hill porosity value) plus 140, a particle penetration of about 5 % or less, of about 3 % or less, or of about 1 % or less, and a Handle-O-Meter stiffness, normalized to basis weight, of about 4 mN / (g / m2) to about 20 mN / (g / m2).

[0488] 91. The sheet of any of embodiments 65 to 81, wherein the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 30 g / m2to about 48 g / m2, a Gurley Hill porosity from about 2 to about 6 seconds, a hydrostatic head from about m cmH2O to about 3000 cmH20, wherein m is (2 times theGurley Hill porosity value) plus 140, a particle penetration of about 5 % or less, of about 3 % or less, or of about 1 % or less, and a Handle-O-Meter stiffness, normalized to basis weight, of about 4 mN / (g / m2) to about 20 mN / fg / m2).

[0489] 92. The sheet of any of embodiments 65 to 81, wherein the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 15 g / m2to about 48 g / m2, a Gurley Hill porosity from about 2 to about 6 seconds, a hydrostatic head from about m CIT1H2O to about 3000 CIT1H2O, wherein m is (2 times the Gurley Hill porosity value) plus 140, a particle penetration of about 5 % or less, and a water vapor transmission rate (WVTR) from about 30,000 g / m2 / day to about 100,000 g / m2 / day, or from about 40,000 g / m2 / day to about 100,000 g / m2 / day.

[0490] 93. The sheet of any of embodiments 65 to 81, wherein the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 30 g / m2to about 48 g / m2, a Gurley Hill porosity from about 2 to about 6 seconds, a hydrostatic head from about m cmH2O to about 3000 cmH20, wherein m is (2 times the Gurley Hill porosity value) plus 140, a particle penetration of about 5 % or less, and a water vapor transmission rate (WVTR) from about 30,000 g / m2 / day to about 100,000 g / m2 / day, or from about 40,000 g / m2 / day to about 100,000 g / m2 / day.

[0491] 94. The sheet of any of embodiments 65 to 81, wherein the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 15 g / m2to about 48 g / m2, a Gurley Hill porosity from about 2 to about 6 seconds, a hydrostatic head from about m cmH2O to about 3000 cmH20, wherein m is (2 times the Gurley Hill porosity value) plus 140, a particle penetration of about 5 % or less, a Handle-O-Meter stiffness, normalized to basis weight, of about 4 mN / (g / m2) to about 20 mN / (g / m2), and a water vapor transmission rate (WVTR) from about 30,000 g / m2 / day to about 100,000 g / m2 / day, or from about 40,000 g / m2 / day to about 100,000 g / m2 / day.

[0492] 95. The sheet of any of embodiments 65 to 81, wherein the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 30 g / m2to about 48 g / m2, a Gurley Hill porosity from about 2 to about 6 seconds, a hydrostatic head from about m cmH2O to about 3000 cmH20, wherein m is (2 times the Gurley Hill porosity value) plus 140, a particle penetration of about 5 % or less, a Handle-O-Meter stiffness, normalized to basis weight, of about 4 mN / (g / m2) to about 20 mN / (g / m2), and a water vapor transmission rate (WVTR) from about 30,000 g / m2 / day to about 100,000 g / m2 / day, or from about 40,000 g / m2 / day to about 100,000 g / m2 / day.

[0493] 96. In some embodiments, the present application provides thermally bonded sheet of nonwoven flash-spun plexifilamentary fibrils, the sheet having

[0494] (a) a basis weight from about 15 g / m2to about 48 g / m2,

[0495] (b) a hydrostatic head of 160 cmH2O or more,(c) a particle penetration of about 5 % or less, and

[0496] (d) a water vapor transmission rate (WVTR) from about 20,000 g / m2 / day to about 100,000 g / m2 / day.

[0497] 97. The sheet embodiment 96 having a hydrostatic head of about 180 cmH2O or more, of about 200 cmH2O or more, or of about 220 cmH2O or more.

[0498] 98. The sheet of any of embodiments 96 to 97 having a basis weight from about 30 g / m2to about 48 g / m2.

[0499] 99. The sheet of any of embodiments 96 to 98 having a Gurley Hill porosity of about 80 seconds or less, or of about 40 seconds or less.

[0500] 100. The sheet of any of embodiments 96 to 99 having a Gurley Hill porosity from about 20 seconds to about 80 seconds, or from about 20 seconds to about 40 seconds.

[0501] 101. The sheet of any of embodiments 96 to 98 having a Gurley Hill porosity from about 2 seconds to about 15 seconds, from about 2 seconds to about 10 seconds, from about 2 seconds to about 6 seconds, from about 6 seconds to about 20 seconds, or from about 10 seconds to about 20 seconds.

[0502] 102. The sheet of any of embodiments 96 to 99 having a particle penetration of about 3 % or less, of about 1 % or less, or of about 0.1 % or less.

[0503] 103. The sheet of any of embodiments 96 to 102 having a particle penetration from about 0.01 % to about 5 %, from about 0.01 % to about 3 %, or from about 0.01 % to about 1 %.

[0504] 104. The sheet of any of embodiments 96 to 103 having a hydrostatic head of about 3000 cmH2O or less, of about 1000 cmH2O or less, of about 800 cmH2O or less, of about 600 cmH2O or less, or of about 500 cmH2O or less.

[0505] 105. The sheet of any of embodiments 96 to 104 having a WVTR of about 30,000 g / m2 / day or more, or of about 40,000 g / m2 / day or more.

[0506] 106. The sheet of any of embodiments 96 to 105 having a WVTR from about 20,000 g / m2 / day to about 100,000 g / m2 / day, from about 20,000 g / m2 / day to about 80,000 g / m2 / day, from about 20,000 g / m2 / day to about 60,000 g / m2 / day, from about 30,000 g / m2 / day to about 100,000 g / m2 / day, from about 30,000 g / m2 / day to about 80,000 g / m2 / day, from about 30,000 g / m2 / day to about 60,000 g / m2 / day, from about 40,000 g / m2 / day to about 100,000 g / m2 / day, from about 40,000 g / m2 / day to about 80,000 g / m2 / day, or from about 40,000 g / m2 / day to about 60,000 g / m2 / day.

[0507] 107. The sheet of any of embodiments 96 to 106 having a Handle-O-Meter stiffness from about 300 mN to about 2000 mN, from about 300 mN to about 1300 mN, from about 300 mN to about 1000 mN, or from about 300 mN to about 800 mN.

[0508] 108. The sheet of any of embodiments 96 to 106 having a Handle-O-Meter stiffness from about 2000 mN to about 8000 mN, from about 2000 mN to about 4000 mN, or from about 4000 mN to about 8000 mN.109. The sheet of any of embodiments 96 to 108 having a Handle-O-Meter stiffness, normalized to basis weight, from about 4 mN / (g / m2) to about 30 mN / (g / m2), from about 4 mN / (g / m2) to about 25 mN / (g / m2), or from about 4 mN / (g / m2) to about 20 mN / (g / m2).

[0509] 110. The sheet of any of embodiments 96 to 108 having a Handle-O-Meter stiffness, normalized to basis weight, from about 30 mN / (g / m2) to about 70 mN / (g / m2), from about 30 mN / (g / m2) to about 60 mN / (g / m2), or from about 30 mN / (g / m2) to about 50 mN / (g / m2).

[0510] 111. The sheet of any of embodiments 96 to 110, wherein the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene.

[0511] 112. The sheet of embodiment 111, wherein the polyethylene is high-density polyethylene (HDPE), or blends / mixtures of high-density polyethylene (HDPE) with low-density polyethylene (LDPE), or blends / mixtures of high-density polyethylene (HDPE) with linear low-density polyethylene (LLDPE).

[0512] 113. The sheet of any of embodiments 96 to 112, wherein the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 15 g / m2to about 48 g / m2, a hydrostatic head of about 160 cmH2O or more, a particle penetration of about 5 % or less, of about 3 % or less, or of about 1 % or less, and a water vapor transmission rate (WVTR) from about 20,000 g / m2 / day to about 100,000 g / m2 / day.

[0513] 114. The sheet of any of embodiments 96 to 112, wherein the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 15 g / m2to about 48 g / m2, a hydrostatic head of about 180 cmH2O or more, a particle penetration of about 5 % or less, of about 3 % or less, or of about 1 % or less, and a water vapor transmission rate (WVTR) from about 20,000 g / m2 / day to about 100,000 g / m2 / day.

[0514] 115. The sheet of any of embodiments 96 to 112, wherein the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 15 g / m2to about 48 g / m2, a hydrostatic head of about 160 cmH2O or more, a particle penetration of about 5 % or less, and a water vapor transmission rate (WVTR) from about 20,000 g / m2 / day to about 100,000 g / m2 / day, and a Handle-O-Meter stiffness, normalized to basis weight, of about 4 mN / (g / m2) to about 30 mN / (g / m2).

[0515] 116. The sheet of any of embodiments 96 to 112, wherein the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 30 g / m2to about 48 g / m2, a hydrostatic head of about 160 cmH2O or more, a particle penetration of about 5 % or less, of about 3 % or less, or of about 1 % or less, and a water vapor transmission rate (WVTR) from about 20,000 g / m2 / day to about 100,000 g / m2 / day.

[0516] 117. The sheet of any of embodiments 96 to 112, wherein the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 30 g / m2to about 48 g / m2, a hydrostatic head of about 160 cmH2O or more, aparticle penetration of about 5 % or less, of about 3 % or less, or of about 1 % or less, and a water vapor transmission rate (WVTR) from about 40,000 g / m2 / day to about 100,000 g / m2 / day.

[0517] 118. The sheet of any of embodiments 96 to 112, wherein the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 30 g / m2to about 48 g / m2, a hydrostatic head of about 200 cmH2O or more, a particle penetration of about 1 % or less, a water vapor transmission rate (WVTR) from about 20,000 g / m2 / day to about 100,000 g / m2 / day, or from about 40,000 g / m2 / day to about 100,000 g / m2 / day.

[0518] 119. In some embodiments, the present application provides thermally bonded sheet of nonwoven flash-spun plexifilamentary fibrils, the sheet having

[0519] (a) a basis weight from about 15 g / m2to about 120 g / m2,

[0520] (b) a hydrostatic head of 220 cmH2O or more,

[0521] (c) a particle penetration of about 1 % or less, and

[0522] (d) a water vapor transmission rate (WVTR) from about 10,000 g / m2 / day to about 100,000 g / m2 / day.

[0523] 120. The sheet of embodiment 119 having a basis weight from about 48 g / m2to about 120 g / m2, from about 63 g / m2to about 120 g / m2, from about 63 g / m2to about 85 g / m2, or from about 63 g / m2to about 75 g / m2.

[0524] 121. The sheet of any of embodiments 119 to 120 having a Gurley Hill porosity of about 80 seconds or less, or of about 40 seconds or less.

[0525] 122. The sheet of any of embodiments 119 to 121 having a Gurley Hill porosity from about 20 seconds to about 80 seconds, or from about 20 seconds to about 40 seconds.

[0526] 123. The sheet of any of embodiments 119 to 122 having a Gurley Hill porosity from about 2 seconds to about 15 seconds, from about 2 seconds to about 10 seconds, from about 2 seconds to about 6 seconds, from about 6 seconds to about 20 seconds, or from about 10 seconds to about 20 seconds.

[0527] 124. The sheet of any of embodiments 119 to 123 having a particle penetration of about 0.1 % or less.

[0528] 125. The sheet of any of embodiments 119 to 124 having a particle penetration from about 0.001 % to about 1 %, or from about 0.01 % to about 1 %.

[0529] 126. The sheet of any of embodiments 119 to 125 having a hydrostatic head of about 3000 CIT1H2O or less, of about 1000 cmH2O or less, of about 800 cmH2O or less, of about 600 cmH2O or less, or of about 500 cmH2O or less.

[0530] 127. The sheet of any of embodiments 119 to 126 having a WVTR of about 20,000 g / m2 / day or more, or of about 30,000 g / m2 / day or more, or of about 40,000 g / m2 / day or more.

[0531] 128. The sheet of any of embodiments 119 to 127 having a WVTR from about 20,000 g / m2 / day to about 100,000 g / m2 / day, from about 20,000 g / m2 / day to about 80,000g / m2 / day, from about 20,000 g / m2 / day to about 60,000 g / m2 / day, from about 30,000 g / m2 / day to about 100,000 g / m2 / day, from about 30,000 g / m2 / day to about 80,000 g / m2 / day, from about 30,000 g / m2 / day to about 60,000 g / m2 / day, from about 40,000 g / m2 / day to about 100,000 g / m2 / day, from about 40,000 g / m2 / day to about 80,000 g / m2 / day, or from about 40,000 g / m2 / day to about 60,000 g / m2 / day.

[0532] 129. The sheet of any of embodiments 119 to 128 having a Handle-O-Meter stiffness from about 300 mN to about 2000 mN, from about 300 mN to about 1300 mN, from about 300 mN to about 1000 mN, or from about 300 mN to about 800 mN.

[0533] 130. The sheet of any of embodiments 119 to 128 having a Handle-O-Meter stiffness from about 2000 mN to about 8000 mN, from about 2000 mN to about 4000 mN, or from about 4000 mN to about 8000 mN.

[0534] 131. The sheet of any of embodiments 119 to 130 having a Handle-O-Meter stiffness, normalized to basis weight, from about 4 mN / (g / m2) to about 30 mN / (g / m2), from about 4 mN / (g / m2) to about 25 mN / (g / m2), or from about 4 mN / (g / m2) to about 20 mN / (g / m2).

[0535] 132. The sheet of any of embodiments 119 to 130 having a Handle-O-Meter stiffness, normalized to basis weight, from about 30 mN / (g / m2) to about 70 mN / (g / m2), from about 30 mN / (g / m2) to about 60 mN / (g / m2), or from about 30 mN / (g / m2) to about 50 mN / (g / m2).

[0536] 133. The sheet of any of embodiments 119 to 132, wherein the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene.

[0537] 134. The sheet of embodiment 133, wherein the polyethylene is high-density polyethylene (HDPE), or blends / mixtures of high-density polyethylene (HDPE) with low-density polyethylene (LDPE), or blends / mixtures of high-density polyethylene (HDPE) with linear low-density polyethylene (LLDPE).

[0538] 135. The sheet of any of embodiments 119 to 134, wherein the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 15 g / m2to about 120 g / m2, a hydrostatic head of about 220 cmH2O or more, a particle penetration of about 1 % or less, and a water vapor transmission rate (WVTR) from about 10,000 g / m2 / day to about 100,000 g / m2 / day, or from about 40,000 g / m2 / day to about 100,000 g / m2 / day.

[0539] 136. The sheet of any of embodiments 119 to 134, wherein the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 15 g / m2to about 120 g / m2, a hydrostatic head of about 220 cmH2O or more, a particle penetration of about 0.1 % or less, and a water vapor transmission rate (WVTR) from about 10,000 g / m2 / day to about 100,000 g / m2 / day.

[0540] 137. The sheet of any of embodiments 119 to 134, wherein the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 15 g / m2to about 120 g / m2, a hydrostatic head of about 220 cmH2O or more, aparticle penetration of about 1 % or less, or of about 0.1 % or less, and a water vapor transmission rate (WVTR) from about 20,000 g / m2 / day to about 100,000 g / m2 / day.

[0541] 138. The sheet of any of embodiments 119 to 134, wherein the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 48 g / m2to about 120 g / m2, a hydrostatic head of about 220 cmH2O or more, a particle penetration of about 1 % or less, a water vapor transmission rate (WVTR) from about 10,000 g / m2 / day to about 100,000 g / m2 / day, and a Handle-O-Meter stiffness, normalized to basis weight, of about 30 mN / (g / m2) to about 70 mN / (g / m2).

[0542] 139. In some embodiments, the present application provides a thermally bonded sheet of nonwoven flash-spun plexifilamentary fibrils, the sheet having

[0543] (a) a basis weight from about 15 g / m2to about 54 g / m2,

[0544] (b) a Frazier porosity from about 0.3 m3 / m2 / min to about 3 m3 / m2 / min,

[0545] (c) a hydrostatic head from about 144 cmH2O to about 1000 cmH2O, and

[0546] (d) a particle penetration of about 1 % or less.

[0547] 140. The sheet embodiment 139 having a hydrostatic head of about 159 cmH2O or more, of about 179 cmH2O or more, or of about 199 cmH2O or more.

[0548] 141. The sheet of any of embodiments 139 to 140 having a basis weight from about 15 g / m2to about 48 g / m2or from about 30 g / m2to about 48 g / m2.

[0549] 142. The sheet of any of embodiments 139 to 141 having a Frazier porosity from about 0.3 m3 / m2 / min to about 1.5 m3 / m2 / min (about 1 ft3 / ft2 / min to about 5 ft3 / ft2 / min).

[0550] 143. The sheet of any of embodiments 139 to 142 having a particle penetration of about 0.1 % or less.

[0551] 144. The sheet of any of embodiments 139 to 143 having a particle penetration from about 0.001 % to about 1 %, or from about 0.01 % to about 1 %.

[0552] 145. The sheet of any of embodiments 139 to 144 having a hydrostatic head of about 800 cmH2O or less, of about 600 cmH2O or less, or of about 500 cmH2O or less.

[0553] 146. The sheet of any of embodiments 139 to 145 having a WVTR of about 20,000 g / m2 / day or more, of about 30,000 g / m2 / day or more, or of about 40,000 g / m2 / day or more.

[0554] 147. The sheet of any of embodiments 139 to 146 having a WVTR from about 20,000 g / m2 / day to about 100,000 g / m2 / day, from about 20,000 g / m2 / day to about 80,000 g / m2 / day, from about 20,000 g / m2 / day to about 60,000 g / m2 / day, from about 30,000 g / m2 / day to about 100,000 g / m2 / day, from about 30,000 g / m2 / day to about 80,000 g / m2 / day, from about 30,000 g / m2 / day to about 60,000 g / m2 / day, from about 40,000 g / m2 / day to about 100,000 g / m2 / day, from about 40,000 g / m2 / day to about 80,000 g / m2 / day, or from about 40,000 g / m2 / day to about 60,000 g / m2 / day.148. The sheet of any of embodiments 139 to 147 having a Handle-O-Meter stiffness from about 300 mN to about 2000 mN, from about 300 mN to about 1300 mN, from about 300 mN to about 1000 mN, or from about 300 mN to about 800 mN.

[0555] 149. The sheet of any of embodiments 139 to 147 having a Handle-O-Meter stiffness from about 2000 mN to about 8000 mN, from about 2000 mN to about 4000 mN, or from about 4000 mN to about 8000 mN.

[0556] 150. The sheet of any of embodiments 139 to 149 having a Handle-O-Meter stiffness, normalized to basis weight, from about 4 mN / (g / m2) to about 30 mN / (g / m2), from about 4 mN / (g / m2) to about 25 mN / (g / m2), or from about 4 mN / (g / m2) to about 20 mN / (g / m2).

[0557] 151. The sheet of any of embodiments 139 to 149 having a Handle-O-Meter stiffness, normalized to basis weight, from about 30 mN / (g / m2) to about 70 mN / (g / m2), from about 30 mN / (g / m2) to about 60 mN / (g / m2), or from about 30 mN / (g / m2) to about 50 mN / (g / m2).

[0558] 152. The sheet of any of embodiments 139 to 151, wherein the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene.

[0559] 153. The sheet of embodiment 152, wherein the polyethylene is high-density polyethylene (HDPE), or blends / mixtures of high-density polyethylene (HDPE) with low-density polyethylene (LDPE), or blends / mixtures of high-density polyethylene (HDPE) with linear low-density polyethylene (LLDPE).

[0560] 154. The sheet of any of embodiments 139 to 153, wherein the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 15 g / m2to about 54 g / m2, a Frazier porosity from about 0.3 m3 / m2 / min to about 3 m3 / m2 / min, a hydrostatic head from about 144 cmH2O to about 1000 cmH2O or from about 159 cmH2O to about 1000 cmH2O, and a particle penetration of about 1 % or less.

[0561] 154. The sheet of any of embodiments 139 to 153, wherein the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 30 g / m2to about 54 g / m2, a Frazier porosity from about 0.3 m3 / m2 / min to about 3 m3 / m2 / min, a hydrostatic head from about 179 cmH2O to about 1000 cmH2O, and a particle penetration of about 1 % or less.

[0562] 156. The sheet of any of embodiments 139 to 153, wherein the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 15 g / m2to about 54 g / m2, a Frazier porosity from about 0.3 m3 / m2 / min to about 3 m3 / m2 / min, a hydrostatic head from about 144 cmH2O to about 1000 cmH2O, a particle penetration of about 1 % or less, and a Handle-O-Meter stiffness, normalized to basis weight, of about 4 mN / (g / m2) to about 30 mN / (g / m2).

[0563] 157. The sheet of any of embodiments 139 to 153, wherein the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 15 g / m2to about 54 g / m2, a Frazier porosity from about 0.3 m3 / m2 / min to about 3m3 / m2 / min, a hydrostatic head from about 159 cmH2O to about 1000 cmH20, and a particle penetration of about 1 % or less.

[0564] 158. The sheet of any of embodiments 139 to 153, wherein the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 15 g / m2to about 54 g / m2, a Frazier porosity from about 0.3 m3 / m2 / min to about 3 m3 / m2 / min, a hydrostatic head from about 159 cmH20 to about 1000 cmH2O, a particle penetration of about 1 % or less, and a Handle-O-Meter stiffness, normalized to basis weight, of about 4 mN / (g / m2) to about 30 mN / (g / m2).

[0565] 159. The sheet of any of embodiments 139 to 153, wherein the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a basis weight from about 15 g / m2to about 54 g / m2, a Frazier porosity from about 0.3 m3 / m2 / min to about 3 m3 / m2 / min, a hydrostatic head from about 144 cmH2O to about 1000 cmH2O, a particle penetration of about 1 % or less, and a water vapor transmission rate (WVTR) from about 20,000 g / m2 / day to about 100,000 g / m2 / day.

[0566] 160. The sheet of any of the preceding embodiments 1 to 159, wherein the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a Ret from about 2 m2Pa / W to about 10 m2Pa / W, from about 2 m2Pa / W to about 8 m2Pa / W, from about 2 m2Pa / W to about 6 m2Pa / W, from about 2 m2Pa / W to about 4 m2Pa / W, from about 4 m2Pa / W to about 6 m2Pa / W, or from about 3 m2Pa / W to about 5 m2Pa / W.

[0567] 161. The sheet of any of the preceding embodiments 1 to 160, wherein the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a blood barrier measured according to ISO 16603 of at least 1.75 kPa, of at least 3.5 kPa, of at least 7 kPa, of at least 14 kPa, or of at least 20 kPa.

[0568] 162. The sheet of any of the preceding embodiments 1 to 161 , wherein the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a viral barrier measured according to ISO 16604 of at least 0 kPa, of at least 1.75 kPa, of at least 3.5 kPa, of at least 7 kPa, of at least 14 kPa, or of at least 20 kPa.

[0569] 163. The sheet of any of the preceding embodiments 1 to 162, wherein the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a blood barrier measured according to ISO 16603 of at least 1.75 kPa and a viral barrier measured according to ISO 16604 of at least 0 kPa, a blood barrier measured according to ISO 16603 of at least 3.5 kPa and a viral barrier measured according to ISO 16604 of at least 1.75 kPa or at least 3.5 kPa, a blood barrier measured according to ISO 16603 of at least 7 kPa and a viral barrier measured according to ISO 16604 of at least 1.75 kPa, at least 3.5 kPa, or at least 7 kPa, a blood barrier measured according to ISO 16603 of at least 14 kPa and a viral barrier measured according to ISO 16604 of at least 3.5 kPa, at least 7 kPa, or at least 14 kPa, or a blood barrier measured according to ISO 16603 of at least 20 kPa and aviral barrier measured according to ISO 16604 of at least 7 kPa, at least 14 kPa, or at least 14 kPa.

[0570] 164. The sheet of any of the preceding embodiments 1 to 163, wherein the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a resistance to chemical permeation, BT-i.o, measured according to ISO 6529 against 10 wt% NaOH or 40 wt% NaOH of 60 min or above, of 120 min or above, of 240 min or above, or of 480 min or above, or a resistance to chemical permeation, BTi.o, measured according to ISO 6529 against 18 wt% H2SO4or 30 wt% H2SO4of 60 min or above, of 120 min or above, of 240 min or above, or of 480 min or above, or both.

[0571] 165. The sheet of any of the preceding embodiments 1 to 164, wherein the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a polyethylene, and the sheet has a crock surface abrasion resistance from 10 to 50 cycles, or from 20 to 50 cycles, or from 30 to 50 cycles, or from 40 to 50 cycles.

[0572] 166. The sheet of any of the preceding embodiments 1 to 165, wherein the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a high-density polyethylene, and the sheet has a Ret from about 2 m2Pa / W to about 8 m2Pa / W, and a blood barrier measured according to ISO 16603 of at least 1.75 kPa, or a viral barrier measured according to ISO 16604 of at least 0 kPa, or both.

[0573] 167. The sheet of any of the preceding embodiments 1 to 166, wherein the flash-spun plexifilamentary fibrils of the bonded sheet are comprised of a high-density polyethylene, and the sheet has a Ret from about 2 m2Pa / W to about 8 m2Pa / W, and a blood barrier measured according to ISO 16603 of at least 1.75 kPa, or a viral barrier measured according to ISO 16604 of at least 0 kPa, or both, and a crock surface abrasion resistance from 20 to 50 cycles.

[0574] 168. In some embodiments, the present application provides a process for the preparation of a sheet of nonwoven flash-spun plexifilamentary fibrils comprises the steps of:

[0575] (i) generating a spin fluid comprising

[0576] (a) from about 8 to about 20 weight percent of a polymer, based on the total amount of the spin fluid, and

[0577] (b) a spin agent comprising one or more hydrocarbons,

[0578] (ii) flash spinning the spin fluid at a temperature at or above about 190 °C and at a pressure that is above the vapor pressure of the spin fluid into a region of essentially atmospheric pressure to form plexifilamentary fibrils of the polymer, (Hi) collecting the plexifilamentary fibrils of the polymer on a collecting means as a sheet of nonwoven flash-spun plexifilamentary fibrils and applying pressure to the sheet to obtain a consolidated sheet,

[0579] (iv) pre-bonding the sheet by warm compression pre-bonding, and

[0580] (v) thermal bonding by whole surface contact bonding of the pre-bonded sheet.169. The process of embodiment 168, wherein the spin fluid comprises the polymer in an amount from about 10 to about 18 weight percent, based on the total amount of the spin fluid, or in an amount from about 12 to about 15 weight percent, based on the total amount of the spin fluid.

[0581] 170. The process of any of embodiments 168 to 169, wherein the flash-spinning is performed at a temperature of 190 °C or above, of 200 °C or above, of 205 °C or above, or of 210 °C or above.

[0582] 171. The process of any of embodiments 168 to 170, wherein the flash-spinning is performed at a temperature from about 190 °C to about 220 °C.

[0583] 172. The process of any of embodiments 168 to 171, wherein the one or more hydrocarbons of the spin agent are selected from n-pentane, cyclopentane, hexane, cyclohexane, 2-methylbutane, 2-methylpentane, 3-methylpentane, 2,2-dimethylbutane, or mixtures thereof.

[0584] 173. The process of any of embodiments 168 to 172, wherein the spin agent comprises n-pentane, cyclopentane, or a mixture thereof.

[0585] 174. The process of any of embodiments 168 to 173, wherein the spin agent comprises, consists essentially of or consists of n-pentane.

[0586] 175. The process of any of embodiments 168 to 173, wherein the spin agent comprises, consists essentially of or consists of a mixture of n-pentane and cyclopentane.

[0587] 176. The process of embodiment 175, wherein the spin agent comprises, consists essentially of, or consists of from about 60 to about 90 weight percent n-pentane and from about 40 to about 10 weight percent cyclopentane, or from about 60 to about 80 weight percent n-pentane and from about 40 to about 20 weight percent cyclopentane.

[0588] 177. The process of embodiments 168 to 173, wherein the spin agent comprises or consists essentially of a mixture of n-pentane, cyclopentane, and a branched hydrocarbon with 5 or 6 carbon atoms.

[0589] 178. The process of embodiment 177, wherein the spin agent comprises, consists essentially of, or consist of a mixture of (1) n-pentane, (2) cyclopentane, and (3) 2-methylbutane, 2-methylpentane, 3-methylpentane, or 2,2-dimethylbutane.

[0590] 179. The process of any of embodiments 177 to 178, wherein the spin agent comprises, consists essentially of, or consist of a mixture of (1) from about 60 to about 85 weight percent n-pentane, (2) from about 13 to about 33 weight percent cyclopentane, and (3) from about 2 to about 7 weight percent 2,2-dimethylbutane, 2-methylpentane, 3-methylpentane, or 2,2-dimethylbutane.

[0591] 180. In some embodiments, the present application provides a process for the preparation of a sheet of nonwoven flash-spun plexifilamentary fibrils comprises the steps of:

[0592] (a) from about 8 to about 11 weight percent of a polymer, and(b) a spin agent comprising a chlorine-containing solvent, selected from dichloromethane, cis-1,2-dichloroethylene, trans- 1 ,2-dichloroethylene, ora mixture of cis-1 ,2-dichloroethylene and trans-1 ,2-dichloroethylene, in combination with a fluorine-containing solvent,

[0593] (ii) flash spinning the spin fluid at a temperature at or above about 190 °C and at a pressure that is above the vapor pressure of the spin fluid into a region of essentially atmospheric pressure to form plexifilamentary fibrils of the polymer, (Hi) collecting the plexifilamentary fibrils of the polymer on a collecting means as a sheet of nonwoven flash-spun plexifilamentary fibrils and applying pressure to the sheet to obtain a consolidated sheet,

[0594] (iv) pre-bonding the sheet by warm compression pre-bonding, and

[0595] (v) thermal bonding by whole surface contact bonding of the pre-bonded sheet. 181. The process of embodiment 180, wherein the spin fluid comprises the polymer in an amount from about 8.0 to about 11.0 weight percent, based on the total amount of the spin fluid, in an amount from about 8.0 to about 10.5 weight percent, based on the total amount of the spin fluid, in an amount from about 8.0 to about 10.0 weight percent, based on the total amount of the spin fluid, or in an amount from about 9.0 to about 11.0 weight percent, based on the total amount of the spin fluid.

[0596] 182. The process of any of embodiments 180 to 181, wherein the flash-spinning is performed at a temperature from about 195 °C to about 230 °C, from about 200 °C to about 220 °C, from about 205 °C to about 220 °C, or from about 210 °C to about 220 °C.

[0597] 183. The process of any of embodiments 180 to 182, wherein the spin agent comprises a chlorine-containing solvent, selected from dichloromethane, cis-1, 2-dichloroethylene, trans-1 ,2-dichloroethylene, ora mixture of cis-1, 2-dichloroethylene and trans-1 ,2-dichloroethylene, in combination with a fluorine-containing solvent which is a linear hydrofluorocarbon having three to six carbon atoms, a cyclic hydrofluorocarbon having four to five carbon atoms, a perfluorocarbon having five to six carbon atoms, or a hydrofluoroether.

[0598] 184. The process of embodiment 183, wherein the linear hydrofluorocarbons having three to six carbon atoms of the spin agent is elected from 1,1,1,3,3-pentafluorobutane, 1H,4H-octafluorobutane, 2H,3H-decafluoropentane, 1H-tridecafluorohexane, or 1H,6H-dodecafluorohexane.

[0599] 185. The process of embodiment 183 or 184, wherein the spin agent comprises, consists essentially, or consists of a mixture of (1) dichloromethane and (2) 1,1,1,3,3-pentafluorobutane, 1H,4H-octafluorobutane, 2H,3H-decafluoropentane, 1H-tridecafluorohexane, or 1H,6H-dodecafluorohexane, or wherein the spin agent comprises, consists essentially, or consists of (1) from about 70 to about 85 weight percent dichloromethane and (2) from about 15 to about 30 weight percent 1,1, 1,3, 3-pentafluorobutane, 1H,4H-octafluorobutane, 2H,3H-decafluoropentane, 1H-tridecafluorohexane, or 1H,6H-dodecafluorohexane, or wherein the spin agent comprises, consists essentially, or consists of (1) from about 75 to about 85 weight percent dichloromethane and (2) from about 15 to about 25 weight percent 1, 1,1, 3,3-pentafluorobutane, 1H,4H-octafluorobutane, 2H,3H-decafluoropentane, 1H-tridecafluorohexane, or 1H,6H-dodecafluorohexane.

[0600] 186. The process of embodiment 183, wherein the cyclic hydrofluorocarbons having four to five carbon atoms of the spin agent is selected from cis-1H,2H-octafluorocyclopentane, trans-1H,2H-octafluorocyclopentane, a mixture of cis-1H,2H-octafluorocyclopentane and trans-1H,2H-octafluorocyclopentane, 1H,1H,2H-heptafluorocyclopentane, or 1, 1,2, 2,3,3-hexafluorocyclopentane.

[0601] 187. The process of embodiment 183 or 186, wherein the spin agent comprises, consists essentially, or consists of a mixture of (1) dichloromethane and (2) cis-1H,2H-octafluorocyclopentane, trans-1H,2H-octafluorocyclopentane, a mixture of cis-1H,2H-octafluorocyclopentane and trans-1H,2H-octafluorocyclopentane, 1H,1H,2H-heptafluorocyclopentane, or 1,1,2,2,3,3-hexafluorocyclopentane

[0602] 188. The process of embodiment 187, wherein the spin agent comprises, consists essentially, or consists of (1) from about 65 to about 80 weight percent dichloromethane and (2) from about 20 to about 35 weight percent cis-1H,2H-octafluorocyclopentane, trans-1H,2H-octafluorocyclopentane, a mixture of cis-1H,2H-octafluorocyclopentane and trans-1H,2H-octafluorocyclopentane, 1H,1H,2H-heptafluorocyclopentane, or 1, 1,2, 2,3,3-hexafluorocyclopentane,

[0603] 189. The process of embodiment 187 or 188, wherein the spin agent comprises, consists essentially, or consists of (1) from about 65 to about 75 weight percent dichloromethane and (2) from about 25 to about 35 weight percent cis-1H,2H-octafluorocyclopentane, trans-1H,2H-octafluorocyclopentane, a mixture of cis-1H,2H-octafluorocyclopentane and trans-1H,2H-octafluorocyclopentane, 1H,1H,2H-heptafluorocyclopentane, or 1, 1,2, 2,3,3-hexafluorocyclopentane.

[0604] 190. The process of embodiment 187, wherein the spin agent comprises, consists essentially, or consists of a mixture of (1) 1 ,2-dichloroethylene and (2) 1, 1,1, 3,3-pentafluorobutane, 1H,4H-octafluorobutane, 2H,3H-decafluoropentane, 1H-tridecafluorohexane, or 1H,6H-dodecafluorohexane.

[0605] 191. The process of embodiment 190, wherein the spin agent comprises, consists essentially, or consists of (1) from about 70 to about 85 weight percent 1 ,2-dichloroethylene and (2) from about 15 to about 30 weight percent 1,1,1,3,3-pentafluorobutane, 1H,4H-octafluorobutane, 2H,3H-decafluoropentane, 1H-tridecafluorohexane, or 1H,6H-dodecafluorohexane.192. The process of embodiment 191, wherein the spin agent comprises, consists essentially, or consists of (1) from about 70 to about 80 weight percent 1 ,2-dichloroethylene and (2) from about 20 to about 30 weight percent 1,1,1,3,3-pentafluorobutane, 1H,4H-octafluorobutane, 2H,3H-decafluoropentane, 1H-tridecafluorohexane, or 1H,6H-dodecafluorohexane.

[0606] 193. The process of embodiment 187, the spin agent comprises, consists essentially, or consists of a mixture of (1) 1,2-dichloroethylene and (2) cis-1H,2H-octafluorocyclopentane, trans-1H,2H-octafluorocyclopentane, a mixture of cis-1H,2H-octafluorocyclopentane and trans- 1H,2H-octafluorocyclopentane, 1H,1H,2H-heptafluorocyclopentane, or 1, 1,2, 2,3,3-hexafluorocyclopentane.

[0607] 194. The process of embodiment 193, wherein the spin agent comprises, consists essentially, or consists of (1) from about 65 to about 80 weight percent 1,2-dichloroethylene and (2) from about 20 to about 35 weight percent cis-1H,2H-octafluorocyclopentane, trans-1H,2H-octafluorocyclopentane, a mixture of cis-1H,2H-octafluorocyclopentane and trans-1H,2H-octafluorocyclopentane, 1H,1H,2H-heptafluorocyclopentane or 1, 1,2, 2,3,3-hexafluorocyclopentane.

[0608] 195. The process of embodiment 194, wherein the spin agent comprises, consists essentially, or consists of (1) from about 65 to about 75 weight percent 1,2-dichloroethylene and (2) from about 20 to about 30 weight percent cis-1H,2H-octafluorocyclopentane, trans-1H,2H-octafluorocyclopentane, a mixture of cis-1H,2H-octafluorocyclopentane and trans-1H,2H-octafluorocyclopentane, 1H,1H,2H-heptafluorocyclopentane, or 1, 1,2, 2,3,3-hexafluorocyclopentane.

[0609] 196. The process of embodiment 187, wherein the spin agent comprises, consists essentially, or consists of a mixture of (1) trans-1 ,2-dichloroethylene and (2) 1,1,1,3,3-pentafluorobutane, 1H,4H-octafluorobutane, 2H,3H-decafluoropentane, 1H-tridecafluorohexane, or 1H,6H-dodecafluorohexane.

[0610] 197. The process of embodiment 196, wherein the spin agent comprises, consists essentially, or consists of (1) from about 70 to about 85 weight percent trans-1, 2-dichloroethylene and (2) from about 15 to about 30 weight percent 1,1,1,3,3-pentafluorobutane, 1H,4H-octafluorobutane, 2H,3H-decafluoropentane, 1H-tridecafluorohexane, or 1H,6H-dodecafluorohexane.

[0611] 198. The process of embodiment 197, wherein the spin agent comprises, consists essentially, or consists of (1) from about 70 to about 80 weight percent trans-1, 2-dichloroethylene and (2) from about 20 to about 30 weight percent 1,1,1,3,3-pentafluorobutane, 1H,4H-octafluorobutane, 2H,3H-decafluoropentane, 1H-tridecafluorohexane, or 1H,6H-dodecafluorohexane.199. The process of embodiment 187, wherein the spin agent comprises, consists essentially, or consists of a mixture of (1) trans-1 ,2-dichloroethylene and (2) 1H,2H-octafluorocyclopentane, cis-1 H,2H-octafluorocyclopentane, trans-1 H,2H-octafluorocyclopentane, 1H,1H,2H-heptafluorocyclopentane, or 1 , 1 ,2, 2,3,3-hexafluorocyclopentane.

[0612] 200. The process of embodiment 199, wherein the spin agent comprises, consists essentially, or consists of (1) from about 65 to about 80 weight percent trans-1 , 2-dichloroethylene and (2) from about 20 to about 35 weight percent cis-1 H,2H-octafluorocyclopentane, trans-1 H,2H-octafluorocyclopentane, a mixture of cis-1 H,2H-octafluorocyclopentane and trans-1 H,2H-octafluorocyclopentane, 1H,1H,2H-heptafluorocyclopentane, or 1 ,1 ,2,2,3,3-hexafluorocyclopentane.

[0613] 201. The process of embodiment 200, wherein the spin agent comprises, consists essentially, or consists of (1) from about 65 to about 75 weight percent trans-1 , 2-dichloroethylene and (2) from about 20 to about 30 weight percent 1H,2H-octafluorocyclopentane, cis-1 H,2H-octafluorocyclopentane, trans-1 H,2H-octafluorocyclopentane, 1H,1H,2H-heptafluorocyclopentane, or 1 , 1 ,2, 2,3,3-hexafluorocyclopentane.

[0614] 202. The process of embodiment 183, wherein the hydrofluoroether is selected from 1-methoxynonafluorobutane or 1 -ethoxynonafluorobutane.

[0615] 203. The process of embodiment 183 or 202, wherein the spin agent comprises, consists essentially, or consists of a mixture of (1) dichloromethane and (2) 1-methoxynonafluorobutane or 1 -ethoxynonafluorobutane.

[0616] 204. The process of embodiment 203, wherein the spin agent comprises, consists essentially, or consists of (1) from about 70 to about 85 weight percent dichloromethane and (2) from about 15 to about 30 weight percent 11 -methoxynonafluorobutane or 1-ethoxynonafluorobutane.

[0617] 205. The process of embodiment 204, wherein the spin agent comprises, consists essentially, or consists of (1) from about 70 to about 80 weight percent dichloromethane and (2) from about 20 to about 30 weight percent 1 -methoxynonafluorobutane or 1-ethoxynonafluorobutane.

[0618] 206. The process of any of embodiments 180 to 205, wherein the flash-spinning is performed at a temperature from about 195 °C to about 230 °C, from about 200 °C to about 220 °C, from about 205 °C to about 230 °C, from about 210 °C to about 220 °C, and wherein the spin fluid comprises about 8.0 to about 11.0 weight percent polymer based on the total amount of the spin fluid.

[0619] 207. The process of any of embodiments 180 to 206, wherein the flash-spinning is performed at a temperature from about 205 °C to about 230 °C, or from about 210 °C to about220 °C, and wherein the spin fluid comprises about 8.0 to about 10.5 weight percent polymer based on the total amount of the spin fluid.

[0620] 208. The process of any of embodiments 180 to 207, wherein the flash-spinning is performed at a temperature from about 205 °C to about 230 °C, or from about 210 °C to about 220 °C, and wherein the spin fluid comprises about 8.0 to about 10.0 weight percent polymer based on the total amount of the spin fluid.

[0621] 209. The process of any of embodiments 147 to 208, wherein the pre-bonding step is performed by heating the consolidated sheet to a temperature between the melting extrapolated onset temperature minus 85 °C (Teim - 85 °C) and the melting extrapolated onset temperature (Teim) in °C of the polymer comprised in the sheet and under a pressure of about 1 bar to about 50 bar.

[0622] 210. The process of embodiment 209, wherein the pre-bonding step is performed under a pressure from about 1 to 50 bar, from about 1 to 30 bar, from about 1 bar to about 15 bar, or from about 5 bar to about 15 bar.

[0623] 211. The process of embodiment 209 or 210, wherein the pre-bonding step is performed by heating the consolidated sheet to a temperature between the melting extrapolated onset temperature minus 65 °C (Teim- 65 °C) and the melting extrapolated onset temperature (Teim) in °C.

[0624] 212. The process of any of embodiments 209 to 211 , wherein the pre-bonding step is performed under a pressure of about 1 bar to about 15 bar.

[0625] 213. The process of any of embodiments 147 to 212, wherein polymer is a polyethylene.

[0626] 214. The process of embodiment 213, wherein the polyethylene is high-density polyethylene (HDPE), or blends / mixtures of high-density polyethylene (HDPE) with low-density polyethylene (LDPE), or blends / mixtures of high-density polyethylene (HDPE) with linear low-density polyethylene (LLDPE).

[0627] 215. The process of any of embodiments 147 to 214, wherein the obtained sheet has (a) a basis weight from about 15 g / m2to about 120 g / m2,

[0628] (b) a Gurley Hill porosity of about 2 seconds or more,

[0629] (c) a hydrostatic head from about y cmH2O to about 3000 cmH2O, wherein y is (2 times the Gurley Hill porosity value) plus 180, and

[0630] (d) a particle penetration of about 7 % or less.

[0631] 216. The process of any of embodiments 147 to 214, wherein the obtained sheet has (a) a basis weight from about 15 g / m2to about 120 g / m2,

[0632] (b) a Gurley Hill porosity of about 20 seconds or more,

[0633] (c) a hydrostatic head from about p cmH2O to about 3000 cmH2O, wherein p is (2 times the Gurley Hill porosity value) plus 140, and

[0634] (d) a particle penetration of about 7 % or less.217. The process of any of embodiments 147 to 214, wherein the obtained sheet has (a) a basis weight from about 15 g / m2to about 48 g / m2,

[0635] (b) a Gurley Hill porosity of about 2 seconds to about 20 seconds,

[0636] (c) a hydrostatic head from about m cmH2O to about 3000 cmH2O, wherein m is (2 times the Gurley Hill porosity value) plus 140, and

[0637] (d) a particle penetration of about 7 % or less.

[0638] 218. The process of any of embodiments 147 to 214, wherein the obtained sheet has (a) a basis weight from about 15 g / m2to about 48 g / m2,

[0639] (b) a hydrostatic head of 160 cmH2O or more,

[0640] (c) a particle penetration of about 5 % or less, and

[0641] (d) a water vapor transmission rate (WVTR) from about 20,000 g / m2 / day to about 100,000 g / m2 / day.

[0642] 219. The process of any of embodiments 147 to 214, wherein the obtained sheet has (a) a basis weight from about 15 g / m2to about 120 g / m2,

[0643] (b) a hydrostatic head of 220 cmH2O or more,

[0644] (c) a particle penetration of about 1 % or less, and

[0645] (d) a water vapor transmission rate (WVTR) from about 10,000 g / m2 / day to about 100,000 g / m2 / day.

[0646] 220. The process of any of embodiments 147 to 214, wherein the obtained sheet has (a) a basis weight from about 15 g / m2to about 54 g / m2,

[0647] (b) a Frazier porosity from about 0.3 m3 / m2 / min to about 3 m3 / m2 / min,

[0648] (c) a hydrostatic head from about 145 cmH2O to about 1000 cmH2O, and

[0649] (d) a particle penetration of about 1 % or less.

[0650] 221. A sheet of nonwoven flash-spun plexifilamentary fibrils obtainable by the process of any one of embodiments 147 to 214.

[0651] 222. A multilayer structure comprising at least one sheet according to any one of embodiments 1 to 146 and at least one further sheet or film.

[0652] 223. Use of a sheet of any of embodiments 1 to 146 for preparing a multilayer structure.

[0653] 224. Use of a sheet of any one of embodiments 1 to 146 or of the multilayer structure of embodiment 222 for the production of packaging.

[0654] 225. An article comprising a sheet of any one of claims 1 to 146 or a multilayer structure of embodiment 222.

[0655] 226. The article of claim 225, wherein the article is selected from protective clothing, outdoor and sports apparel, active packaging, covers for equipment including car covers, and cargo covers.

[0656] 227. The article of embodiment 225 or 226, comprising a bonded sheet of flash-spun plexifilamentary fibrils of polyethylene, wherein the article has a basis weight from about15 g / m2to about 54 g / m2, a Ret from about 2 m2Pa / Wto about 10 m2Pa / W, and a blood barrier measured according to ISO 16603 of at least 1.75 kPa, or a viral barrier measured according to ISO 16604 of at least 0 kPa, or both.

[0657] 228. An article comprising a bonded sheet of flash-spun plexifilamentary fibrils of polyethylene, wherein the article has a basis weight from about 15 g / m2to about 54 g / m2, a Ret from about 2 m2Pa / W to about 10 m2Pa / W, and a blood barrier measured according to ISO 16603 of at least 1.75 kPa, or a viral barrier measured according to ISO 16604 of at least 0 kPa, or both.

[0658] 229. The article of any of embodiments 227 to 228 having a basis weight from about 15 g / m2to about 54 g / m2, from about 30 g / m2to about 54 g / m2, from about 33 g / m2to about 48 g / m2, from about 39 g / m2to about 48 g / m2, from about 39 g / m2to about 43 g / m2, from about 33 g / m2to about 37 g / m2, from about 34 g / m2to about 40 g / m2, from about 43 g / m2to about 48 g / m2, or from about 48 g / m2to about 54 g / m2.

[0659] 230. The article of any of embodiments 227 to 229 having a Ret from about 2 m2Pa / W to about 10 m2Pa / W, from about 2 m2Pa / W to about 8 m2Pa / W, from about 2 m2Pa / W to about 6 m2Pa / W, from about 2 m2Pa / Wto about 4 m2Pa / W, from about 4 m2Pa / Wto about 6 m2Pa / W, or from about 3 m2Pa / W to about 5 m2Pa / W.

[0660] 231. The article of any of embodiments 227 to 230 having a blood barrier measured according to ISO 16603 of at least 1.75 kPa, of at least 3.5 kPa, of at least 7 kPa, of at least 14 kPa, or of at least 20 kPa.

[0661] 232. The article of any of embodiments 227 to 231 having a viral barrier measured according to ISO 16604 of at least 0 kPa, of at least 1.75 kPa, of at least 3.5 kPa, of at least 7 kPa, of at least 14 kPa, or of at least 20 kPa.

[0662] 233. The article of any of embodiments 227 to 232 having a blood barrier measured according to ISO 16603 of at least 1.75 kPa and a viral barrier measured according to ISO 16604 of at least 0 kPa, a blood barrier measured according to ISO 16603 of at least 3.5 kPa and a viral barrier measured according to ISO 16604 of at least 1.75 kPa or at least 3.5 kPa, a blood barrier measured according to ISO 16603 of at least 7 kPa and a viral barrier measured according to ISO 16604 of at least 1.75 kPa, at least 3.5 kPa, or at least 7 kPa, a blood barrier measured according to ISO 16603 of at least 14 kPa and a viral barrier measured according to ISO 16604 of at least 3.5 kPa, at least 7 kPa, or at least 14 kPa, or a blood barrier measured according to ISO 16603 of at least 20 kPa and a viral barrier measured according to ISO 16604 of at least 7 kPa, at least 14 kPa, or at least 14 kPa.

[0663] 234. The article of any of embodiments 227 to 233 having a crock surface abrasion resistance from 10 to 50 cycles, or from 20 to 150 cycles, or from 30 to 50 cycles, or from 40 to 50 cycles.235. The article of any of embodiments 227 to 234 having a resistance to chemical permeation, BTij0, measured according to ISO 6529 against 10 wt% NaOH of 60 min or above, of 120 min or above, of 240 min or above, or of 480 min or above.

[0664] 236. The article of any of embodiments 227 to 235 having a resistance to chemical permeation, BT-i.o, measured according to ISO 6529 against 40 wt% NaOH of 60 min or above, of 120 min or above, of 240 min or above, or of 480 min or above.

[0665] 237. The article of any of embodiments 227 to 236 having a resistance to chemical permeation, BT1 0, measured according to ISO 6529 against 18wt% H2SO4of 60 min or above, of 120 min or above, of 240 min or above, or of 480 min or above.

[0666] 238. The article of any of embodiments 227 to 237 having a resistance to chemical permeation, BT1 0, measured according to ISO 6529 against 30 wt% H2SO4of 60 min or above, of 120 min or above, of 240 min or above, or of 480 min or above.

[0667] 239. The article of any of embodiments 227 to 238 having a resistance to chemical permeation, BT-i.o, measured according to ISO 6529 against 10 wt% NaOH of 60 min or above, of 120 min or above, of 240 min or above, or of 480 min or above and having a resistance to chemical permeation, BTi|0, measured according to ISO 6529 against 18 wt% H2SO4of 60 min or above, of 120 min or above, of 240 min or above, or of 480 min or above.

[0668] 240. The article of any of embodiments 227 to 239 having a resistance to chemical permeation, BT-i o, measured according to ISO 6529 against 40 wt% NaOH of 60 min or above, of 120 min or above, of 240 min or above, or of 480 min or above and having a resistance to chemical permeation, BT1 0, measured according to ISO 6529 against 30 wt% H2SO4of 60 min or above, of 120 min or above, of 240 min or above, or of 480 min or above.

[0669] 241. The article of any of embodiments 227 to 240 having a Handle-O-Meter stiffness, normalized to basis weight, of about 1 mN / (g / m2) to about 30 mN / (g / m2), of about 1 mN / (g / m2) to about 20 mN / (g / m2), of about 2 mN / (g / m2) to about 10 mN / (g / m2), of about 2 mN / (g / m2) to about 5 mN / (g / m2), or of about 10 mN / (g / m2) to about 30 mN / (g / m2).

[0670] 242. The article of any of embodiments 227 to 241 having a Ret from about 2 m2Pa / W to about 8 m2Pa / W, and a blood barrier measured according to ISO 16603 of at least 1.75 kPa, or a viral barrier measured according to ISO 16604 of at least 0 kPa, or both, ora blood barrier measured according to ISO 16603 of at least 3.5 kPa, or a viral barrier measured according to ISO 16604 of at least 1.75 kPa, or at least 3.5 kPa, or both.

[0671] 243. The article of any of embodiments 227 to 241 having a Ret from about 2 m2Pa / W to about 8 m2Pa / W, and a blood barrier measured according to ISO 16603 of at least 7 kPa, or a viral barrier measured according to ISO 16604 of at least 1.75 kPa, at least 3.5 kPa, or at least 7 kPa, or both, or a blood barrier measured according to ISO 16603 of at least 14 kPa, or a viral barrier measured according to ISO 16604 of at least 3.5 kPa, at least 7 kPa, or at least 14 kPa, or both.244. The article of any of embodiments 227 to 241 having a Ret from about 2 m2Pa / W to about 8 m2Pa / W, and a blood barrier measured according to ISO 16603 of at least 1.75 kPa, or a viral barrier measured according to ISO 16604 of at least 0 kPa, or both, ora blood barrier measured according to ISO 16603 of at least 3.5 kPa, or a viral barrier measured according to ISO 16604 of at least 1.75 kPa, or at least 3.5 kPa, or both, and a resistance to chemical permeation, BTi,0, measured according to ISO 6529 against 10 wt% NaOH or against 40 wt% NaOH of 60 min or above, of 120 min or above, of 240 min or above, or of 480 min or above, or a resistance to chemical permeation, BTi.o, measured according to ISO 6529 against 18 wt% H2SO4or 30 wt% H2SO4of 60 min or above, of 120 min or above, of 240 min or above, or of 480 min or above.

[0672] 245. The article of any of embodiments 227 to 241 having a Ret from about 2 m2Pa / W to about 8 m2Pa / W, and a blood barrier measured according to ISO 16603 of at least 7 kPa, or a viral barrier measured according to ISO 16604 of at least 1.75 kPa, at least 3.5 kPa, or at least 7 kPa, or both, or a blood barrier measured according to ISO 16603 of at least 14 kPa, or a viral barrier measured according to ISO 16604 of at least 3.5 kPa, at least 7 kPa, or at least 14 kPa, or both, and a resistance to chemical permeation, BTi.o, measured according to ISO 6529 against 10 wt% NaOH or against 40 wt% NaOH of 60 min or above, of 120 min or above, of 240 min or above, or of 480 min or above, or a resistance to chemical permeation, BT10, measured according to ISO 6529 against 18 wt% H2SO4or 30 wt% H2SO4of 60 min or above, of 120 min or above, of 240 min or above, or of 480 min or above.

[0673] 246. The article of any of embodiments 227 to 241 having a Ret from about 2 m2Pa / W to about 8 m2Pa / W, and a blood barrier measured according to ISO 16603 of at least 1.75 kPa, or a viral barrier measured according to ISO 16604 of at least 0 kPa, or both, ora blood barrier measured according to ISO 16603 of at least 3.5 kPa, or a viral barrier measured according to ISO 16604 of at least 1.75 kPa, or at least 3.5 kPa, or both, and a crock surface abrasion resistance from 10 to 100 cycles, or from 20 to 100 cycles, or from 30 to 100 cycles, or from 40 to 100 cycles, or from 50 to 100 cycles.

[0674] 247. The article of any of embodiments 227 to 241 having a Ret from about 2 m2Pa / W to about 8 m2Pa / W, and a blood barrier measured according to ISO 16603 of at least 7 kPa, or a viral barrier measured according to ISO 16604 of at least 1.75 kPa, at least 3.5 kPa, or at least 7 kPa, or both, or a blood barrier measured according to ISO 16603 of at least 14 kPa, or a viral barrier measured according to ISO 16604 of at least 3.5 kPa, at least 7 kPa, or at least 14 kPa, or both, and a crock surface abrasion resistance from 10 to 50 cycles, or from 20 to 50 cycles, or from 30 to 50 cycles, or from 40 to 50 cycles.

[0675] 248. The article of any of embodiments 227 to 241 having a Ret from about 2 m2Pa / W to about 8 m2Pa / W, and a blood barrier measured according to ISO 16603 of at least 1.75 kPa, or a viral barrier measured according to ISO 16604 of at least 0 kPa, or both, ora blood barriermeasured according to ISO 16603 of at least 3.5 kPa, or a viral barrier measured according to ISO 16604 of at least 1.75 kPa, or at least 3.5 kPa, or both, and a Handle-O-Meter stiffness, normalized to basis weight, of about 1 mN / (g / m2) to about 30 mN / (g / m2), of about 1 mN / (g / m2) to about 20 mN / (g / m2), of about 2 mN / (g / m2) to about 10 mN / (g / m2), of about 2 mN / (g / m2) to about 5 mN / (g / m2), or of about 10 mN / (g / m2) to about 30 mN / (g / m2).

[0676] 249. The article of any of embodiments 227 to 241 having a Ret from about 2 m2Pa / W to about 8 m2Pa / W, and a blood barrier measured according to ISO 16603 of at least 7 kPa, or a viral barrier measured according to ISO 16604 of at least 1.75 kPa, at least 3.5 kPa, or at least 7 kPa, or both, or a blood barrier measured according to ISO 16603 of at least 14 kPa, or a viral barrier measured according to ISO 16604 of at least 3.5 kPa, at least 7 kPa, or at least 14 kPa, or both, and a Handle-O-Meter stiffness, normalized to basis weight, of about 1 mN / (g / m2) to about 30 mN / (g / m2), of about 1 mN / (g / m2) to about 20 mN / (g / m2), of about 2 mN / (g / m2) to about 10 mN / (g / m2), of about 2 mN / (g / m2) to about 5 mN / (g / m2), or of about 10 mN / (g / m2) to about 30 mN / (g / m2).

[0677] 250. The article of any of embodiments 227 to 241 having a Ret from about 2 m2Pa / W to about 6 m2Pa / W, and a blood barrier measured according to ISO 16603 of at least 7 kPa, or a viral barrier measured according to ISO 16604 of at least 1.75 kPa, or at least 3.5 kPa, or at least 7 kPa, or both, or a blood barrier measured according to ISO 16603 of at least 14 kPa, or a viral barrier measured according to ISO 16604 of at least 3.5 kPa, at least 7 kPa, or at least 14 kPa, or both, or a blood barrier measured according to ISO 16603 of at least 20 kPa, or a viral barrier measured according to ISO 16604 of at least 7 kPa, at least 14 kPa, or at least 20 kPa, or both.

[0678] 251. The article of any of embodiments 227 to 241 having a Ret from about 2 m2Pa / W to about 6 m2Pa / W, and a blood barrier measured according to ISO 16603 of at least 7 kPa, or a viral barrier measured according to ISO 16604 of at least 1.75 kPa, or at least 3.5 kPa, or at least 7 kPa, or both, or a blood barrier measured according to ISO 16603 of at least 14 kPa, or a viral barrier measured according to ISO 16604 of at least 3.5 kPa, at least 7 kPa, or at least 14 kPa, or both, or a blood barrier measured according to ISO 16603 of at least 20 kPa, or a viral barrier measured according to ISO 16604 of at least 7 kPa, at least 14 kPa, or at least 20 kPa, or both, and a resistance to chemical permeation, BT-i.o, measured according to ISO 6529 against 10 wt% NaOH or against 40 wt% NaOH of 60 min or above, of 120 min or above, of 240 min or above, or of 480 min or above, or a resistance to chemical permeation, BTi.o, measured according to ISO 6529 against 18 wt% H2SO4or 30 wt% H2SO4of 60 min or above, of 120 min or above, of 240 min or above, or of 480 min or above.

[0679] 252. The article of any of embodiments 227 to 241 having a Ret from about 2 m2Pa / W to about 6 m2Pa / W, and a blood barrier measured according to ISO 16603 of at least 7 kPa, or a viral barrier measured according to ISO 16604 of at least 1.75 kPa, or at least 3.5 kPa, or atleast 7 kPa, or both, or a blood barrier measured according to ISO 16603 of at least 14 kPa, or a viral barrier measured according to ISO 16604 of at least 3.5 kPa, at least 7 kPa, or at least 14 kPa, or both, or a blood barrier measured according to ISO 16603 of at least 20 kPa, or a viral barrier measured according to ISO 16604 of at least 7 kPa, at least 14 kPa, or at least 20 kPa, or both, and a crock surface abrasion resistance from 10 to 50 cycles, or from 20 to 50 cycles, or from 30 to 50 cycles, or from 40 to 50 cycles.

[0680] 253. The article of any of embodiments 227 to 241 having a Ret from about 2 m2Pa / W to about 6 m2Pa / W, and a blood barrier measured according to ISO 16603 of at least 7 kPa, or a viral barrier measured according to ISO 16604 of at least 1.75 kPa, at least 3.5 kPa, or at least 7 kPa, or both, or a blood barrier measured according to ISO 16603 of at least 14 kPa, or a viral barrier measured according to ISO 16604 of at least 3.5 kPa, at least 7 kPa, or at least 14 kPa, or both, or a blood barrier measured according to ISO 16603 of at least 20 kPa, or a viral barrier measured according to ISO 16604 of at least 7 kPa, at least 14 kPa, or at least 20 kPa, or both, and a crock surface abrasion resistance from 10 to 50 cycles, or from 20 to 50 cycles, or from 30 to 50 cycles, or from 40 to 50 cycles, and a Handle-O-Meter stiffness, normalized to basis weight, of about 1 mN / (g / m2) to about 30 mN / (g / m2), of about 1 mN / (g / m2) to about 20 mN / (g / m2), of about 2 mN / fg / m2) to about 10 mN / (g / m2), of about 2 mN / (g / m2) to about 5 mN / (g / m2), or of about 10 mN / (g / m2) to about 30 mN / (g / m2).

[0681] 254. The article of any of embodiments 227 to 241 having a basis weight from about 48 g / m2to about 54 g / m2, a Ret from about 2 m2Pa / W to about 6 m2Pa / W, and a blood barrier measured according to ISO 16603 of at least 20 kPa, or a viral barrier measured according to ISO 16604 of at least 7 kPa, at least 14 kPa, or at least 20 kPa, or both.

[0682] 255. The article of any of the preceding embodiments 227 to 254, wherein the outside of the clothing is embossed with a linen pattern, a rib pattern or a point pattern, or wherein the inside of the clothing is embossed with a linen pattern, a rib pattern or a point pattern, wherein the embossing pattern on the outside and the inside of the clothing can be the same or different.

[0683] 256. The article of any of the preceding embodiments 227 to 255, wherein the polyethylene is a high-density polyethylene (HDPE), a blend or mixture of a high-density polyethylene (HDPE) with low-density polyethylene (LDPE), or a blend or mixture of a high-density polyethylene (HDPE) with linear low-density polyethylene (LLDPE).

[0684] 257. The article of any of embodiments 227 to 256 selected from protective clothing, protective covers, gowns, drapes, shoe covers, operating back-table covers, equipment covers for operating and biological and drug manufacturing processes, portable biohazard tents and enclosures, isolation fabrics, emergency shelters, mobile operating containment enclosures, and sterilization wraps.258. The article of any of the preceding embodiments 227 to 257 which is a single-layer protective clothing.

[0685] 259. The article of any of the preceding embodiments 227 to 258 which is a protective clothing and which comprises, consists essentially of, or consists of pieces of one or more single-layer bonded sheets of flash-spun plexifilamentary fibers, at least one stitched seam comprising a yarn, optionally at least one zipper, and optionally one or more elastic bands.

[0686] While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example, and not limitation. It will be apparent to persons skilled in the relevant art(s) that various changes in form and detail can be made therein without departing from the spirit and scope of the present invention. Thus, it should be appreciated that, while the invention has been described with reference to the above exemplary embodiments, other embodiments are within the scope of the claims. Moreover, it should be understood that the exemplary embodiments described herein may be combined to form other embodiments. After reading the above description, it will be apparent to one skilled in the relevant art(s) how to implement the invention in alternative embodiments. Thus, the present invention should not be limited by any of the above-described exemplary embodiments.

Claims

CLAIMS1. A thermally bonded sheet of nonwoven flash-spun plexifilamentary fibrils, the sheet having(a) a basis weight from about 15 g / m2to about 120 g / m2,(b) a Gurley Hill porosity of about 2 seconds or more,(c) a hydrostatic head from about y cmH2O to about 3000 cmH2O, wherein y is (2 times the Gurley Hill porosity value) plus 180, and(d) a particle penetration of about 7 % or less.

2. The sheet of claim 1 having a hydrostatic head from about y cmH2O to about 3000 cmH2O, wherein y is (2 times the Gurley Hill porosity value) plus 195 or plus 205.

3. A thermally bonded sheet of nonwoven flash-spun plexifilamentary fibrils, the sheet having(a) a basis weight from about 15 g / m2to about 120 g / m2,(b) a Gurley Hill porosity of about 20 seconds or more,(c) a hydrostatic head from p cmH2O to about 3000 cmH2O, wherein p is (2 times the Gurley Hill porosity value) plus 140, and(d) a particle penetration of about 7 % or less.

4. The sheet of claim 3 having a hydrostatic head from about p cmH2O to about 3000 cmH2O, wherein p is (2 times the Gurley Hill porosity value) plus 155 or plus 180 or plus 195 or plus 205.

5. A thermally bonded sheet of nonwoven flash-spun plexifilamentary fibrils, the sheet having(a) a basis weight from about 15 g / m2to about 48 g / m2,(b) a Gurley Hill porosity of about 2 seconds to about 20 seconds,(c) a hydrostatic head from m cmH2O to about 3000 cmH2O, wherein m is (2 times the Gurley Hill porosity value) plus 140, and(d) a particle penetration of about 7 % or less.

6. The sheet of claim 5 having a hydrostatic head from about m cmH2O to about 3000 cmH2O, wherein m is (2 times the Gurley Hill porosity value) plus 155 or plus 180 or plus 195 or plus 205.

7. The sheet of any one of claims 1 to 6 having a particle penetration of about 5 % or less or about 3 % or less, or about 1 % or less.

8. The sheet of any one of claims 1 to 7 having a WVTR of from about 10,000 g / m2 / day to about 100,000 g / m2 / day.

9. A thermally bonded sheet of nonwoven flash-spun plexifilamentary fibrils, the sheet having(a) a basis weight from about 15 g / m2to about 48 g / m2,(b) a hydrostatic head of 160 cmH2O or more,(c) a particle penetration of about 5 % or less, and(d) a water vapor transmission rate (WVTR) from about 20,000 g / m2 / day to about 100,000 g / m2 / day.

10. The sheet of claim 9 having a hydrostatic head of 180 cmH2O or more, or of 200 cmH2O or more, or of 220 cmH2O or more.

11. The sheet of any one of claims 9 to 10 having a water vapor transmission rate (WVTR) of about 30,000 g / m2 / day or more, or of about 40,000 g / m2 / day or more.

12. A thermally bonded sheet of nonwoven flash-spun plexifilamentary fibrils, the sheet having(a) a basis weight from about 15 g / m2to about 120 g / m2,(b) a hydrostatic head of 220 cmH2O or more,(c) a particle penetration of about 1 % or less, and(d) a water vapor transmission rate (WVTR) from about 10,000 g / m2 / day to about 100,000 g / m2 / day.

13. The sheet of claim 12 having a water vapor transmission rate (WVTR) of about 20,000 g / m2 / day or more.

14. A thermally bonded sheet of nonwoven flash-spun plexifilamentary fibrils, the sheet having(a) a basis weight from about 15 g / m2to about 54 g / m2,(b) a Frazier porosity from about 0.3 m3 / m2 / min to about 3 m3 / m2 / min,(c) a hydrostatic head from about 144 cmH2O to about 1000 cmH2O, and(d) a particle penetration of about 1 % or less.

15. The sheet of claim 14 having a hydrostatic head of about 179 cmH2O or more, or of about 199 cmH20 or more.

16. The sheet of claims 14 or 15 having a WVTR of from about 20,000 g / m2 / day to about 100,000 g / m2 / day.

17. A process for the preparation of a sheet of nonwoven flash-spun plexifilamentary fibrils comprises the steps of:(i) generating a spin fluid comprising(a) from about 8 to about 20 weight percent of a polymer, based on the total amount of the spin fluid, and(b) a spin agent comprising one or more hydrocarbons,(ii) flash spinning the spin fluid at a temperature at or above about 190 °C and at a pressure that is above the vapor pressure of the spin fluid into a region of essentially atmospheric pressure to form plexifilamentary fibrils of the polymer, (iii) collecting the plexifilamentary fibrils of the polymer on a collecting means as a sheet of nonwoven flash-spun plexifilamentary fibrils and applying pressure to the sheet to obtain a consolidated sheet,(iv) pre-bonding the sheet by warm compression pre-bonding, and(v) thermal bonding by whole surface contact bonding of the pre-bonded sheet.

18. A process for the preparation of a sheet of nonwoven flash-spun plexifilamentary fibrils comprises the steps of:(a) from about 8 to about 11 weight percent of a polymer, and(b) a spin agent comprising a chlorine-containing solvent, selected from dichloromethane, cis-1,2-dichloroethylene, trans- 1 ,2-dichloroethylene, ora mixture of cis-1 ,2-dichloroethylene and trans-1 ,2-dichloroethylene, in combination with a fluorine-containing solvent,(ii) flash spinning the spin fluid at a temperature at or above about 190 °C and at a pressure that is above the vapor pressure of the spin fluid into a region of essentially atmospheric pressure to form plexifilamentary fibrils of the polymer, (iii) collecting the plexifilamentary fibrils of the polymer on a collecting means as a sheet of nonwoven flash-spun plexifilamentary fibrils and applying pressure to the sheet to obtain a consolidated sheet,(iv) pre-bonding the sheet by warm compression pre-bonding, and(v) thermal bonding by whole surface contact bonding of the pre-bonded sheet.

19. The process of any of claims 17 to 18, wherein the pre-bonding step is performed by heating the consolidated sheet to a temperature between the melting extrapolated onset temperature minus 85 °C (Teim- 85 °C) and the melting extrapolated onset temperature (Teim) in °C of the polymer comprised in the sheet and under a pressure of about 1 bar to about 50 bar.

20. A multilayer structure comprising at least one sheet according to any one of claims 1 to 16 and at least one further sheet or film.

21. Use of the sheet of any one of claims 1 to 16 for preparing a multilayer structure.

22. Use of a sheet of any one of claims 1 to 16 or of the multilayer structure of claim 20 for the production of packaging.

23. An article comprising a sheet of any one of claims 1 to 16 or a multilayer structure of claim 20.

24. The article of claim 23, wherein the article is selected from protective clothing, outdoor and sports apparel, active packaging, covers for equipment including car covers, and cargo covers.

25. The article of claim 23 or 24, said article comprising a bonded sheet of flash-spun plexifilamentary fibrils of polyethylene according to any of claims 1 to 16, wherein the article has a basis weight from about 15 g / m2to about 54 g / m2, a Ret from about 2 m2Pa / W to about 10 m2Pa / W, and a blood barrier measured according to ISO 16603 of at least 1.75 kPa, or a viral barrier measured according to ISO 16604 of at least 0 kPa, or both.

26. An article comprising a bonded sheet of flash-spun plexifilamentary fibrils of polyethylene, wherein the article has a basis weight from about 15 g / m2to about 54 g / m2, a Ret from about 2 m2Pa / W to about 10 m2Pa / W, and a blood barrier measured according to ISO 16603 of at least 1.75 kPa, or a viral barrier measured according to ISO 16604 of at least 0 kPa, or both.

27. The article according to claim 25 or 26, wherein the article has a basis weight from about 30 g / m2to about 48 g / m2, a Ret from about 2 m2Pa / W to about 8 m2Pa / W, a blood barrier measured according to ISO 16603 of at least 3.5 kPa, or a viral barrier measuredaccording to ISO 16604 of at least 1.75 kPa, or at least 3.5 kPa, or both, and a resistance to chemical permeation, BT-i.o, measured according to ISO 6529 against 10 wt% NaOH and against 18 wt% H2SO4of 60 min or above, of 120 min or above, of 240 min or above, or of 480 min or above.

28. The article according to any one of claims 23 to 27, wherein the article is selected from protective clothing, protective covers, gowns, drapes, shoe covers, operating back-table covers, equipment covers for operating processes, equipment covers for biological and drug manufacturing processes, portable biohazard tents and enclosures, isolation fabrics, emergency shelters, mobile operating containment enclosures, and sterilization wraps.

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