A lightweight, lead-free, breathable nuclear protective garment and method of making the same

Abstract

The present application relates to the technical field of nuclear protective clothing, and particularly relates to a lightweight, lead-free and breathable nuclear protective clothing and a preparation method thereof. The preparation method comprises the following steps: blending BWWT composite shielding particles and polypropylene to prepare a master batch, melt spinning the master batch to form nascent fibers after modification, and performing ultrasonic cavitation and electrostatic field synergistic treatment on the nascent fibers, and then performing heat stretching and setting to obtain composite fibers; subsequently, the composite fibers are carded and laid, and are subjected to needle punching treatment and supercritical carbon dioxide treatment to obtain a 3D composite fiber needle punched fabric; meanwhile, bismuth solution is coated on a modified polyimide film twice and is hot pressed to obtain a lightweight lead-free protective material; finally, the two are connected by a sewing process to obtain the nuclear protective clothing.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of nuclear protective clothing, and particularly relates to a lightweight, lead-free and breathable nuclear protective clothing and a preparation method thereof. BACKGROUND

[0002] In the field of nuclear radiation protection, traditional nuclear protective clothing generally uses lead-containing materials as shielding layers, but it has significant defects: on the one hand, the high density of lead leads to heavy protective clothing, poor wearing comfort and affects the flexibility of operation; on the other hand, lead is a toxic heavy metal, and there is environmental pollution and human health risk in the production and use process. With the development of radiation protection technology, lead-free, lightweight and breathable comfort have become an urgent need in the industry.

[0003] Although existing lead-free nuclear protective materials attempt to use bismuth-based and tungsten-based shielding particles as alternative materials, the shielding particles (such as bismuth oxide and tungsten oxide) are prone to agglomeration in the polymer matrix, leading to uneven dispersion and forming weak shielding areas, especially under high-energy radiation, the attenuation efficiency decreases significantly. In addition, the traditional fabric structure cannot balance the shielding performance and the breathable performance, and the dense shielding layer will hinder the flow of air and water vapor, causing heat and moisture to accumulate in the parts prone to sweating (such as underarms, neck, back, etc.) of the wearer, which seriously affects the comfort and safety of long-time operation.

[0004] Therefore, developing a preparation method of nuclear protective clothing with high-efficiency shielding, lightweight lead-free and breathable performance has become the key to solving the existing problems. SUMMARY

[0005] The present application overcomes the shortcomings of the prior art and provides a lightweight, lead-free and breathable nuclear protective clothing and a preparation method thereof.

[0006] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows: a preparation method of a lightweight, lead-free and breathable nuclear protective clothing, comprising the following steps:

[0007] Step one: blending BWWT composite shielding particles and polypropylene to obtain a master batch, modifying the master batch and then melt spinning to form a composite fiber; after the composite fiber is carded and directionally laid into a composite fiber web, needle punching and supercritical carbon dioxide treatment are performed to obtain a 3D composite fiber needle-punched fabric; wherein the modified master batch is melt spun to obtain a nascent fiber, and the nascent fiber is subjected to ultrasonic cavitation and electrostatic field synergistic treatment;

[0008] Step two: twice coating bismuth solution on the modified polyimide film and hot pressing to obtain a lightweight lead-free protective material;

[0009] Step three: connecting the 3D composite fiber needle-punched fabric and the lightweight lead-free protective material through a sewing process to obtain a nuclear protective clothing;

[0010] The ultrasonic cavitation and electrostatic field synergistic treatment is a treatment in an inert environment at an ultrasonic frequency of 38 to 42 kHz and an electrostatic field intensity of -30 to -20 kV for 3 to 7 min, and the needle punching treatment adopts a needle density of 120 needles / cm 2 to 150 needles / cm 2 and a penetration depth of 1.6 to 2.0 mm.

[0011] Further, the preparation method of the 3D composite fiber needle-punched fabric comprises:

[0012] S1: melt blending and extruding the BWWT composite shielding particles and polypropylene to obtain a master batch;

[0013] S2: melt spinning the master batch after surface modification to form nascent fibers, and performing ultrasonic cavitation and electrostatic field synergistic treatment on the nascent fibers to obtain composite fibers after heat stretching and setting;

[0014] S3: carding the composite fibers after fixed-length cutting to form a single-layer fiber web, and directionally laying up the single-layer fiber web to obtain a composite fiber web;

[0015] S4: performing air curtain guidance and needle punching treatment on the composite fiber web to obtain a needle-punched fabric intermediate;

[0016] S5: performing gradient heat pressing and pressure maintaining and cooling on the preheated needle-punched fabric intermediate to obtain a compression-set fabric;

[0017] S6: performing supercritical carbon dioxide treatment and rapid pressure relief on the compression-set fabric, and performing hot roller rolling and cooling setting to obtain a 3D composite fiber needle-punched fabric;

[0018] The gradient heat pressing comprises the following three continuous pressure stages:

[0019] the first stage applies a pressure of 0.4-0.6 MPa for 8-12 s;

[0020] the second stage applies a pressure of 2.5-3.0 MPa for 17-23 s;

[0021] and the third stage applies a pressure of 5.0-6.0 MPa for 25-35 s.

[0022] Further, the preparation method of the master batch comprises:

[0023] dry mixing 55-65 wt% bismuth oxide, 10-20 wt% tungsten oxide, 10-20 wt% tungsten carbide, and 5-15 wt% tantalum oxide at 750-850 rpm for 10-15 min to form BWWT composite shielding particles;

[0024] The 30-40 wt% polypropylene and 60-70 wt% BWWT composite shielding particles are melt blended at a temperature field of 165-190 ℃ and a rotation speed of 110-130 rpm for 3-5 min; after removing impurities with a diameter greater than 50 μm by filtration, the strip-shaped melt is extruded through a 1-3 mm die, cooled in a 22-28 ℃ circulating water tank, and finally cut into a cylindrical master batch with a length of 1-6 mm, a diameter of 1-3 mm.

[0025] Further, the master batch modification method comprises: putting the master batch into a KH560 silane coupling agent ethanol solution with a pH of 4.0-5.0 and a concentration of 1-3 wt%, refluxing at 65-75 ℃ with a stirring speed of 180-220 rpm for 80-100 min; after reaction, filtering, washing with anhydrous ethanol for 3-5 times, and vacuum drying at 75-85 ℃ for 3-5 h to obtain the modified master batch.

[0026] Further, the method for heat stretching and setting comprises: introducing the primary fibers treated by ultrasonic cavitation and electrostatic field into an environment at 130-140 ℃, and performing orientation and crystallization regulation at a stretching ratio of 1.9-2.3, and setting by a cooling roller at 22-28 ℃ to obtain the composite fibers.

[0027] Further, the method for fixed-length cutting comprises: cutting the composite fibers into fixed-length fiber bundles with a length of 5.0-8.0 cm.

[0028] Further, the mass per unit area of the single-layer fiber web is 0.045-0.055 g / cm 2 .

[0029] Further, the method for preparing the lightweight lead-free protective material comprises the following steps:

[0030] M1: modifying the polyimide film to obtain a modified polyimide film;

[0031] M2: coating a bismuth solution on the modified polyimide film to form a wet film, and after heat pressing treatment, a composite film intermediate with a bismuth coating layer is obtained;

[0032] M3: coating a bismuth solution on the surface of the composite film intermediate to form a wet film, and after heat pressing treatment, a composite film with a thickened bismuth coating layer is obtained;

[0033] M4: calendering the composite film, and after cooling and setting, a lightweight lead-free protective material is obtained;

[0034] The heat pressing treatment comprises preheating at 265-275 ℃ and 0.05-0.2 MPa for 19-21 min, and then pressing at 290-300 ℃ and 24-26 MPa for 14-16 min.

[0035] Further, the sewing process comprises the following steps:

[0036] T1: cutting the 3D composite fiber needle-punched fabric and the lightweight lead-free protective material into pieces respectively, cutting the pieces and spraying a functional glue layer;

[0037] T2: sewing the processed pieces together;

[0038] T3: attaching a hot melt adhesive tape at the joint and pulse hot pressing and bonding;

[0039] T4: melt sealing the joint.

[0040] The present application provides still another technical solution: a lightweight, lead-free, breathable nuclear protective clothing prepared by the above preparation method, comprising an easy-to-sweat part and other parts, wherein the easy-to-sweat part is a 3D composite fiber needle-punched fabric, and the other parts are lightweight lead-free protective materials.

[0041] The present application solves the defects in the background art, and has the following beneficial effects:

[0042] The present application adopts the synergistic treatment of specific ultrasonic frequency and electrostatic field intensity in an inert environment on the primary fiber, the strong impact force is released when the transient cavitation bubbles generated by ultrasonic cavitation collapse, and the agglomerates in the BWWT composite shielding particles are broken; at the same time, the surface of the bismuth oxide particles modified by KH560 is positively charged by the electrostatic field, and the directional electrostatic repulsion force between adjacent particles resists the re-agglomeration caused by van der Waals force, realizes the uniform dispersion of BWWT composite shielding particles in the polypropylene matrix, reduces the local shielding blind area, and the interfacial bonding force between the particles and the matrix is enhanced. Compared with the easy agglomeration of high-filled particles in the prior art, which leads to local shielding blind area and weak interfacial bonding between particles and matrix, the preparation method provided by the present application improves the uniformity of the radiation shielding of the nuclear protective clothing, and at the same time, the elongation at break is also improved, avoiding the problem of easy breakage caused by local stress concentration.

[0043] The present application adopts 120-150 needles / cm 2 of needle density and 1.6-2.0 mm of penetration depth to needle-punch the composite fiber web, so that the needles form moderate entanglement in the fiber web, which can not only ensure sufficient cohesion between the fibers to maintain the stability of the structure, but also will not excessively compress the pores between the fibers, preserving the uniformity and connectivity of the pores, maintaining the good pore structure of the composite fiber web, ensuring that air and water vapor can pass smoothly, and at the same time ensuring the stability of the intermediate structure of the needle-punched fabric. Compared with the problems of air permeability and structural stability caused by pore collapse or loose structure in the prior art, the present application improves the air permeability and moisture permeability under the premise of ensuring the stability of the 3D composite fiber needle-punched fabric structure, and enhances the wear comfort of the nuclear protective clothing.

[0044] The present application is based on ultrasonic cavitation and electrostatic field synergistic treatment to realize uniform dispersion of particles, and based on needle punching treatment to optimize fiber entanglement and pore structure; wherein, uniform dispersion of particles reduces local stress concentration, enhances fiber and particle interface bonding, is conducive to uniform entanglement of fibers and stable formation of pore structure in the needle punching process, so that the protective clothing shows more stable and efficient shielding performance in a wide energy spectrum range, while having excellent air permeability, moisture permeability and mechanical toughness, realizing unified improvement of protection efficiency and wearing comfort, and overcoming the performance limitations caused by particle agglomeration and uneven structure in the prior art. BRIEF DESCRIPTION OF DRAWINGS

[0045] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments described in the present application, and other drawings can also be obtained by those skilled in the art without creative labor on the basis of these drawings;

[0046] Figure 1 A flow chart of a preparation method of a lightweight, lead-free, air-permeable nuclear protective clothing;

[0047] Figure 2 A flow chart of a preparation method of a 3D composite fiber needle punched fabric;

[0048] Figure 3 A flow chart of a preparation method of a lightweight lead-free protective material;

[0049] Figure 4 A flow chart of a sewing process. DETAILED DESCRIPTION

[0050] In the following description, many specific details are set forth in order to provide a thorough understanding of the present application, but the present application can also be implemented in other ways different from those described herein, therefore, the scope of protection of the present application is not limited by the specific embodiments disclosed below. In the following examples, all raw materials are obtained from commercial or prepared by conventional methods in the art. Among them, the following materials are purchased from Sinopharm: bismuth oxide, tungsten oxide, tungsten carbide and tantalum oxide (purity greater than 99%), KH560 silane coupling agent, KH550 silane coupling agent; polyimide film is purchased from Alfa (ThermoFisher); tungsten powder (99.9%, 200 nm), bismuth powder (99.99%, 200 mesh) are purchased from Macklin Reagent.

[0051] As shown in Figure 1 A preparation method of a lightweight, lead-free, air-permeable nuclear protective clothing, comprising the following steps:

[0052] Step one: blend BWWT composite shielding particles with polypropylene to obtain master batch, melt spinning after modification of the master batch to form composite fibers; after carding and directional laying of the composite fiber web, needle punching treatment and supercritical carbon dioxide treatment, 3D composite fiber needle-punched fabric is prepared; wherein, the master batch is melt spun after modification to obtain as-spun fibers, and the as-spun fibers are treated by ultrasonic cavitation and electrostatic field synergy;

[0053] Step two: twice coating bismuth solution on the modified polyimide film and hot pressing to obtain lightweight lead-free protective material;

[0054] Step three: connecting 3D composite fiber needle-punched fabric and lightweight lead-free protective material through sewing process to obtain nuclear protective clothing.

[0055] As shown in Figure 2 A method for preparing 3D composite fiber needle-punched fabric, comprising the following steps:

[0056] S1: melt blending and extruding BWWT composite shielding particles and polypropylene to obtain master batch;

[0057] S2: melt spinning as-spun fibers after surface modification of the master batch, treating the as-spun fibers by ultrasonic cavitation and electrostatic field synergy, and obtaining composite fibers after heat stretching and setting;

[0058] S3: carding single-layer fiber web after cutting the composite fibers to a fixed length, and directional laying the single-layer fiber web to obtain composite fiber web;

[0059] S4: air curtain guiding and needle punching treatment of the composite fiber web to obtain needle-punched fabric intermediate;

[0060] S5: gradient hot pressing and pressure maintaining cooling of the preheated needle-punched fabric intermediate to obtain compression set fabric;

[0061] S6: supercritical carbon dioxide treatment and rapid pressure relief of the compression set fabric, and 3D composite fiber needle-punched fabric is obtained after hot roller rolling and cooling setting.

[0062] Next, each step will be described in detail.

[0063] In step S1, first mix BWWT composite shielding particles, then melt blend and extrude BWWT composite shielding particles and polypropylene according to the proportion, and finally cool and cut to obtain master batch.

[0064] Specifically, the pre-dried bismuth oxide, tungsten oxide, tungsten carbide, and tantalum oxide are dry-mixed at 750-850 rpm for 10-15 min in a mass ratio of bismuth oxide 55-65 wt%, tungsten oxide 10-20 wt%, tungsten carbide 10-20 wt%, and tantalum oxide 5-15 wt% to form BWWT composite shielding particles. Simultaneously, the polypropylene is subjected to drying treatment.

[0065] Then, the pre-dried polypropylene and the BWWT composite shielding particles are melt-blended at a temperature of 165-190 °C and a rotational speed of 110-130 rpm for 3-5 min in a mass ratio of polypropylene 30-40 wt% and BWWT composite shielding particles 60-70 wt%. After removing impurities with a diameter greater than 50 μm by filtration, the melt is extruded into a strip through a 1-3 mm die, solidified in a 22-28 °C circulating water cooling tank, and finally cut into a master batch with a length of 1-6 mm, a diameter of 1-3 mm, and a cylindrical shape.

[0066] During the melt-blending process, the polypropylene molecular chains are oriented under the action of shear, and the agglomerates of the BWWT composite shielding particles are mechanically broken; among them, the bismuth oxide undergoes plastic deformation and fills the gaps between the hard particles such as tungsten oxide and tungsten carbide, and the tungsten carbide penetrates into the gaps between the polypropylene molecular chains to form mechanical anchoring points.

[0067] In step S2, the master batch is first surface-modified to obtain a modified master batch, the modified master batch is melt-spun to form a nascent fiber, the nascent fiber is then subjected to ultrasonic cavitation and electrostatic field synergistic treatment, and finally heat stretching and setting are performed to obtain a composite fiber.

[0068] Specifically, the surface modification method includes placing the dried master batch into a KH560 silane coupling agent anhydrous ethanol solution with a pH of 4.0-5.0 and a concentration of 1-3 wt% (liquid-solid mass ratio 4-6:1), and refluxing at 65-75 °C under stirring at a rotational speed of 180-220 rpm for 80-100 min. After the reaction, the master batch is filtered, washed with anhydrous ethanol for 3-5 times, and vacuum dried at 75-85 °C for 3-5 h to obtain a modified master batch.

[0069] During the surface modification process, only the bismuth oxide is significantly modified by reacting with KH560 due to the presence of hydroxyl groups on its surface, and the tungsten oxide reacts in small amounts, while the tungsten carbide, tantalum oxide, and polypropylene matrix do not participate in the reaction.

[0070] The method of melt spinning includes putting the KH560 covalently grafted bismuth oxide surface modified BWWT / PP master batch into a spinning machine, melt extruding at a cylinder temperature of 170-190°C and a screw rotation speed of 45-55 rpm. The melt is extruded through a spinneret with a diameter of 0.18-0.22 mm, an extrusion speed of 0.7-0.9 m / s, and is introduced into a water cooling tank at 22-28°C for solidification to obtain nascent fibers with a diameter of 0.25-0.35 mm.

[0071] The method of ultrasonic cavitation and electrostatic field synergistic treatment includes continuously introducing the nascent fibers into an ultrasonic cavitation and electrostatic field synergistic treatment tank at a speed of 7.0-8.0 m / min, and the tank contains deoxygenated anhydrous ethanol (liquid level height of 14-16 cm). An ultrasonic transducer is installed at the bottom and both side walls of the tank, and parallel plate electrodes are arranged on the upper and lower parts of the tank body (the upper electrode is negative and the lower electrode is positive) to form an electrostatic field, and the direction of the electric field is perpendicular to the direction of the nascent fibers. High-purity nitrogen is continuously introduced into the tank at a flow rate of 1.5-2.5 L / min to maintain an inert environment with an oxygen concentration of not more than 500 ppm, and the treatment is carried out at an ultrasonic frequency of 38-42 kHz and an electrostatic field strength of -20 to -30 kV for 3-7 min.

[0072] The high-frequency sound waves generated by the ultrasonic transducer form periodic pressure fluctuations in the anhydrous ethanol, causing a large number of transient cavitation bubbles to be generated inside the liquid. When the bubbles collapse, the strong impact force released directly acts on the BWWT composite shielding particle agglomerates inside the nascent fibers, and the brittle tungsten oxide is preferentially broken and depolymerized. At the same time, the electrostatic field formed by the upper and lower electrode plates makes the KH560 modified bismuth oxide particles on the surface positively charged, and directional electrostatic repulsion forces are generated between adjacent particles, effectively resisting re-agglomeration caused by van der Waals forces, and achieving uniform dispersion of the particles in the fiber matrix.

[0073] The method of heat stretching and setting includes introducing the fibers treated by ultrasonic cavitation and electrostatic field synergistic treatment into an environment at 130-140°C, orienting and crystallizing at a draw ratio of 1.9-2.3, and setting on a cooling roller at 22-28°C to obtain composite fibers.

[0074] In step S3, the composite fibers are cut to a fixed length and carded into a single-layer fiber web, and then oriented and stacked to form a composite fiber web.

[0075] Specifically, the method of cutting to a fixed length includes cutting the composite fibers into fixed-length fiber bundles of 5-8 cm.

[0076] The method of carding into a single-layer fiber web includes conveying the fixed-length fiber bundles to a carding device, and carding at a cylinder rotation speed of 750-850 rpm and a doffer rotation speed of 22-28 rpm to form a single-layer fiber web with a mass per unit area of 0.04-0.06 g / cm 2The single-layer fiber web is obtained by carding the mixture of the tungsten oxide particles and the bismuth oxide particles. In the carding process, the static electricity generated by the friction of the fibers causes the negatively charged tungsten oxide particles and the positively charged bismuth oxide particles to spontaneously gradiently distribute.

[0077] The method of directional laying includes sequentially laying the single-layer fiber web with 5-10 layers, and keeping the fiber web in a fluffy state to obtain a composite fiber web.

[0078] In step S4, the composite fiber web is subjected to air curtain guiding and needle punching to form a needle-punched fabric intermediate.

[0079] Specifically, the method of air curtain guiding includes guiding the composite fiber web into an air curtain guiding area at a speed of 0.7-0.9 m / min, and treating the fiber web with a laminar flow air curtain (temperature 22-28 ℃) flowing vertically downward at a speed of 0.8-1.2 m / s for 0.4-0.6 min, so that the fibers are kept in a fluffy and uniform distribution.

[0080] The method of needle punching includes guiding the fiber web after the air curtain guiding into a needle punching device, and performing needle punching operation on the fiber web according to a preset path by using pressure feedback needles, the needle punching density being 120-150 needles / cm 2 , the penetration depth being 1.6-2.0 mm, and the frequency being 550-650 needles / min. After completing a stroke of 8-12 cm, the surface temperature of the fabric is monitored in real time, and when the local temperature exceeds 50 ℃, an air cooling spraying system is triggered (spraying time 2.5-3.5 s), and finally a needle-punched fabric intermediate with a thickness of 3-5 mm is formed.

[0081] In the needle punching process, the pressure feedback needles maintain the penetration depth stable by adjusting the driving parameters, and ensure uniform fiber entanglement; the high-hardness tantalum oxide is easy to generate local heat by friction with the needles, and the tungsten carbide enhances the fiber hooking through the angular structure and promotes the formation of a three-dimensional structure.

[0082] In step S5, the needle-punched fabric intermediate is preheated and then subjected to gradient heat pressing, and then is cooled under pressure to obtain a compression-shaped fabric.

[0083] Specifically, the method of preheating includes feeding the needle-punched fabric intermediate into a preheating channel (temperature 75-85 ℃) at a speed of 0.45-0.55 m / min, and treating the fabric for 2-5 min.

[0084] The preheated needle-punched fabric intermediate is transferred to a hot press (upper and lower press plate temperature 95-105 ℃) for three-stage gradient heat pressing from low to high.

[0085] In the first stage, a pressure of 0.4-0.6 MPa is applied for 8-12 s; the pressure in this stage is relatively low, and is used to compact the surface fibers of the needle-punched fabric intermediate;

[0086] The second stage applies a pressure of 2.5-3.0 MPa for 17-23 s; the pressure is significantly increased in this stage, which can effectively pass through the middle layer of the fabric and promote the further slippage, entanglement and densification of the main fiber network of the needle-punched fabric intermediate body;

[0087] The third stage applies a pressure of 5.0-6.0 MPa for 25-35 s; the high pressure in this stage finally ensures that the core layer of the needle-punched fabric intermediate body is fully compacted, and the fiber stress is relaxed under a hot environment.

[0088] By controlling the rate and duration of the step-by-step increase in pressure, the fibers in the entire needle-punched fabric intermediate body are guided to be orderly and gradually compressed and shaped from the surface to the inside, avoiding problems such as over-compaction of the surface layer, insufficient compaction of the inside, or fiber damage caused by single high pressure, thereby achieving uniform compression.

[0089] The method of pressure holding and cooling includes maintaining the pressure until the fabric temperature drops to 37-43℃, opening the pressure plate, and outputting the compression-shaped fabric at a speed of 0.9-1.1 m / min through the roller, and fixing the compression deformation.

[0090] In step S5, the compression-shaped fabric is treated with supercritical carbon dioxide, then quickly depressurized and hot-rolled, and finally cooled and shaped to obtain a 3D composite fiber needle-punched fabric.

[0091] Specifically, the method of supercritical carbon dioxide treatment includes placing the compression-shaped fabric in a supercritical carbon dioxide treatment kettle, sealing it, heating it to above 31℃, and pressurizing it to above 7.4 MPa, and maintaining it for 25-40 min.

[0092] The method of rapid depressurization includes reducing the pressure to normal pressure within 0.5-1 s at a rate of 8-10 MPa / s.

[0093] The method of hot roller compaction includes guiding the treated compression-shaped fabric into a double-roller hot compactor, and rolling it three times at a speed of 0.75-0.85 m / min under the conditions of a roller surface temperature of 95-105℃ and a linear pressure of 0.4-0.6 MPa.

[0094] The method of cooling and shaping includes shaping the rolled fabric through a 23-27℃ cooling air duct to obtain a 3D composite fiber needle-punched fabric.

[0095] Supercritical carbon dioxide forms a fluid state with both gas diffusivity and liquid solubility above the critical temperature and above the critical pressure. Its molecules can penetrate into the free volume of the polypropylene amorphous region and form an enrichment layer at the interface of the BWWT composite shielding particles and polypropylene due to the difference in interfacial energy. When the pressure drops suddenly, the dissolved carbon dioxide is quickly precipitated from the polypropylene matrix due to supersaturation, and micropore nucleation is initiated in the amorphous region, where the corners of tungsten carbide become preferential nucleation points.

[0096] As shown in Figure 3 A method for preparing a lightweight lead-free protective material, comprising the following steps:

[0097] M1: modifying the polyimide film to obtain a modified polyimide film;

[0098] M2: coating a bismuth solution on the modified polyimide film to form a wet film, and after heat pressing treatment, obtaining a composite film intermediate with a bismuth coating layer;

[0099] M3: coating a bismuth solution on the surface of the composite film intermediate to form a wet film, and after heat pressing treatment, obtaining a composite film with a thickened bismuth coating layer;

[0100] M4: calendering the composite film, and after cooling and setting, obtaining a lightweight lead-free protective material.

[0101] Specifically, the method of modification in step M2 includes immersing the polyimide film in a 0.9-1.1 wt% KH550 silane coupling agent ethanol solution, treating at 45-55℃ for 4.5-5.5 min, and then drying with hot air at 75-85℃ for 9-11 min to form a modified layer to enhance the bonding force of the surface and the subsequent coating layer, obtaining a modified polyimide film.

[0102] In step M2, the preparation method of the bismuth solution includes mixing bismuth oxide (65-75 wt%), tantalum oxide (20-30 wt%), and tungsten carbide (0-10 wt%), and ultrasonic dispersion mixing with anhydrous ethanol in a mass ratio of 1:2.5-3.5 to obtain a bismuth solution.

[0103] The coating method includes coating the bismuth solution on the surface of the modified polyimide film at a rate of 230-270 mm / min to form a wet film of 180-220 μm.

[0104] The method of hot pressing treatment includes sending the modified polyimide film after coating into a hot press, preheating at 265-275℃, 0.05-0.2 MPa for 19-21 min, then increasing the temperature to 290-300℃, 24-26 MPa for 14-16 min to make the bismuth-based shielding particles tightly stacked and firmly combined with the modified polyimide film base; finally, pressure holding and cooling to a temperature lower than 80℃ to obtain a composite film intermediate with a bismuth coating.

[0105] In step M3, the method of secondary coating includes re-coating the bismuth coating surface of the composite film intermediate with the same specification bismuth solution at a rate of 230-270 mm / min to form a wet film of 180-220 μm; the method of hot pressing treatment is the same as step M2 to obtain a composite film with a thickened bismuth coating.

[0106] In step M4, the method of calendering treatment includes feeding the composite film into a calender at a rate of 32-38 m / min, setting the upper roller temperature to 95-105℃, the middle roller to 80-90℃, the lower roller to 70-80℃, the roller gap to 0.9-1.1 mm, and the linear pressure to 450-550 N / cm.

[0107] The method of cooling and setting includes guiding the calendered composite film into a cooling roller set at 22-28℃ for setting to obtain a lightweight lead-free protective material.

[0108] As shown in Figure 4 , a sewing process includes the following steps.

[0109] T1: cutting the 3D composite fiber needle-punched fabric and the lightweight lead-free protective material into pieces, cutting and spraying a functional adhesive layer on the cut pieces;

[0110] T2: sewing and connecting the treated cut pieces;

[0111] T3: attaching a hot melt adhesive tape at the seam and pulse hot pressing and bonding;

[0112] T4: melt sealing the seam.

[0113] Specifically, the method of stepwise cutting in step T1 includes cutting the seam edges (width 5-10 mm) of the 3D composite fiber needle-punched fabric and the lightweight lead-free protective material pieces, and adjusting the cutting angle to form mutually matching inclined contact surfaces in the seam contact area. The cutting slope of the seam edge of the 3D composite fiber needle-punched fabric is 10-20°, and the cutting slope of the seam edge of the lightweight lead-free protective material is 20-30° (the slopes of the two are different to adapt to the thickness characteristics of the materials), to ensure that the edges are tightly fitted during sewing and avoid steps or gaps.

[0114] The method for spraying the functional adhesive layer includes spraying an epoxy resin adhesive solution of 60-70 wt% tungsten powder on the surface of the sutured contact area after cutting, curing at 75-85 ℃ for 3-10 min, and forming a 0.1-0.5 mm thick functional adhesive layer to enhance the sealing and bonding of the joint.

[0115] In step T2, the method for suture connection includes using a nitinol suture to perform double-line lock suture along the sutured contact area at a speed of 800 stitches / min, with a stitch length of 1.9-2.1 mm, to ensure firm connection of the two layers of materials.

[0116] In step T3, the method for pulse hot pressing includes preattaching a hot melt adhesive tape of 78-82 wt% bismuth powder to the joint, and pulse hot pressing at 118-122 ℃ and 0.45-0.55 MPa for 4.5-5.5 s, so that the edges of the adhesive tape cover both sides of the suture by 2.8-3.2 mm, to strengthen the joint bonding strength.

[0117] In step T4, a hot melt of 185-195 ℃ thermoplastic polyurethane (die gap 0.33-0.37 mm) is extruded along the joint, and a hot air (air speed 2.8-3.2 m / s) at 98-102 ℃ is used to assist the spread of the melt, so that the sealing layer covers both sides of the hot melt adhesive tape by 0.9-1.1 mm; finally, the suture process is completed by using a 14-16 ℃ cooling roller to shape.

[0118] A lightweight, lead-free, and breathable nuclear protective clothing is prepared by the above preparation method, and includes easy-to-sweat parts and other parts. The easy-to-sweat parts are 3D composite fiber needle-punched fabrics, and the other parts are lightweight lead-free protective materials. It should be noted that the easy-to-sweat parts refer to areas with high metabolism and dense sweat gland distribution, such as underarms, neck, back, palm, and groin. These areas tend to accumulate heat and sweat during activities, and the use of 3D composite fiber needle-punched fabrics with better breathability ensures comfort.

[0119] Example 1:

[0120] Step 1, preparation of 3D composite fiber needle-punched fabric:

[0121] S1: Dry mix bismuth oxide 60 wt%, tungsten oxide 15 wt%, tungsten carbide 15 wt%, and tantalum oxide 10 wt% at 800 rpm for 15 min to form BWWT composite shielding particles. Blend 35 wt% polypropylene with 65 wt% BWWT composite shielding particles at a temperature of 180 ℃ and a rotation speed of 120 rpm for 5 min. After removing impurities with a diameter greater than 50 μm by filtration, extrude the strip-shaped melt through a 2 mm die, pass it through a 25 ℃ circulating water cooling tank for solidification, and cut it into cylindrical pellets with a length of 3 mm and a diameter of 2 mm.

[0122] S2: The master batch was put into a solution of KH560 silane coupling agent in anhydrous ethanol with a pH of 4.5 and a concentration of 2 wt% (liquid-solid mass ratio of 5:1), and refluxed at 70 °C and 200 rpm for 90 min. After filtration, the master batch was washed with anhydrous ethanol three times and vacuum dried at 80 °C for 4 h to obtain a modified master batch. The modified master batch was put into a spinning machine and melt-extruded at a barrel temperature of 180 °C and a screw rotation speed of 50 rpm. The melt was extruded through a 0.2 mm spinneret at a linear speed of 0.8 m / s and then solidified in a water cooling tank at 25 °C to obtain nascent fibers with a diameter of 0.3 mm.

[0123] The nascent fibers were introduced into a treatment tank containing deoxygenated anhydrous ethanol (liquid level of 15 cm) at a speed of 7.5 m / min. An ultrasonic transducer was installed at the bottom and side wall of the tank, and an electrostatic field was formed between the upper and lower electrodes (direction perpendicular to the fiber running direction). High-purity nitrogen gas (oxygen concentration < 500 ppm) was introduced at a flow rate of 2 L / min. The fibers were treated under an ultrasonic frequency of 40 kHz and an electrostatic field strength of -20 kV for 3 min. Subsequently, the fibers were introduced into an environment at 135 °C and heat-drawn at a draw ratio of 2.1, and then shaped by a cooling roller at 25 °C to obtain composite fibers.

[0124] S3: The composite fibers were cut into 6 cm length fiber bundles. The fiber bundles were sent to a carding device, and the fibers were separated into single-layer fiber webs with a mass per unit area of 0.05 g / cm 2 under the conditions of a cylinder rotation speed of 800 rpm and a doffer rotation speed of 25 rpm. Seven single-layer fiber webs were grabbed and directionally laid to form a composite fiber web in a fluffy state.

[0125] S4: The composite fiber web was introduced into a gas curtain control area at a speed of 0.8 m / min and treated by a vertical laminar air curtain at a temperature of 25 °C and a flow rate of 1.0 m / s for 0.5 min. Subsequently, the fiber web was introduced into a needle punching device, and needle punched at a density of 120 needles / cm 2 , a penetration depth of 1.6 mm, and a frequency of 600 strokes / min. If the local temperature exceeded 50 °C, compressed air cooling was triggered for 3 s after every 10 cm of travel. Finally, a needle-punched fabric intermediate with a thickness of 4 mm was formed.

[0126] S5: The needle-punched fabric intermediate was sent into a preheating channel at a speed of 0.5 m / min and treated at a temperature of 80 °C for 3 min. The fabric was then transferred to a hot press at a temperature of 100 °C and pressed in three stages: 10 s at a pressure of 0.5 MPa, 20 s at a pressure of 2.7 MPa, and the remaining time at a pressure of 5.5 MPa. The pressure was maintained until the fabric temperature dropped to 40 °C, and the fabric was then output at a speed of 1.0 m / min to obtain a compression-shaped fabric.

[0127] S6: The compressed shaped fabric was placed in a supercritical carbon dioxide treatment kettle, heated to 31.1 ℃, pressurized to 7.39 MPa, and maintained for 30 min; it was depressurized to normal pressure at a rate of 8 MPa / s within 1 s, introduced into a double-roller hot calender (100 ℃ roller surface temperature, 0.5 MPa linear pressure), and calendered 3 times at a rate of 0.8 m / min, shaped in a 25 ℃ cooling air duct, and a 3D composite fiber needle-punched fabric was obtained.

[0128] Step two, lightweight lead-free protective material:

[0129] M1: The polyimide film was immersed in a 1.0 wt% KH550 silane coupling agent ethanol solution, treated at 50 ℃ for 5 min, and then hot air dried at 80 ℃ for 10 min to obtain a modified polyimide film.

[0130] M2: Bismuth oxide 70 wt%, tantalum oxide 25 wt%, tungsten carbide 5 wt% were mixed, and dispersed with absolute ethanol at a mass ratio of 1:3 for 20 min under ultrasonic waves at 40 kHz to obtain a bismuth solution with a viscosity of 5000 mPa·s. The bismuth solution was coated on the surface of the modified polyimide film at a rate of 250 mm / min to form a 200 μm wet film; the film was sent into a hot press, preheated at 270 ℃ and 0.1 MPa for 20 min, and then pressed at 295 ℃ and 25 MPa for 15 min, and pressure-cooled to 70 ℃ to obtain a composite film intermediate with a bismuth coating;

[0131] M3: The bismuth coating surface of the composite film intermediate was coated with bismuth solution again at the same rate (200 μm wet film), and the above hot pressing treatment was repeated to obtain a composite film with a thickened bismuth coating.

[0132] M4: The composite film was fed into a calender at a rate of 35 m / min, with the upper roller at 100 ℃, the middle roller at 85 ℃, the lower roller at 75 ℃, a roller gap of 1.0 mm, and a linear pressure of 500 N / cm; after calendering, it was introduced into a 25 ℃ cooling roller group for shaping to obtain a lightweight lead-free protective material.

[0133] Step three, suturing process:

[0134] T1: The 3D composite fiber needle-punched fabric and the lightweight lead-free protective material were cut into pieces, and the edges of the two were sutured and cut: the 3D composite fiber needle-punched fabric edge was cut at an angle of 15°, the lightweight lead-free protective material edge was cut at an angle of 25°, a matching inclined contact surface was formed, and a 0.3 mm thick functional glue layer was formed by spraying a 65 wt% tungsten powder epoxy resin glue solution on the contact surface and curing at 80 ℃ for 5 min;

[0135] T2: Nitinol suture was used to perform double-line lock suture along the contact area at a rate of 800 stitches / min;

[0136] T3: 80 wt% bismuth powder hot melt tape is attached to the joint, and pulse hot pressing is carried out at 120°C and 0.5 MPa for 5s;

[0137] T4: 190°C thermoplastic polyurethane melt is extruded along the joint, and 100°C, 3.0 m / s hot air assisted spreading is simultaneously performed, and the joint is completed by 15°C cooling roller shaping, to obtain a lightweight, lead-free, breathable nuclear protective clothing.

[0138] Example 2:

[0139] In this embodiment, the difference from Example 1 is that the electrostatic field strength in S2 is-25 kV; the needle density in S4 is 135 needles / cm 2 , and the penetration depth is 1.8 mm.

[0140] Example 3:

[0141] In this embodiment, the difference from Example 1 is that the electrostatic field strength in S2 is-30 kV; the needle density in S4 is 150 needles / cm 2 , and the penetration depth is 2.0 mm.

[0142] Example 4:

[0143] In this embodiment, the difference from Example 1 is that the treatment time in S2 is 5 min, and the electrostatic field strength is-20 kV; the needle density in S4 is 150 needles / cm 2 , and the penetration depth is 1.6 mm.

[0144] Example 5:

[0145] In this embodiment, the difference from Example 1 is that the treatment time in S2 is 5 min, and the electrostatic field strength is-25 kV; the needle density in S4 is 135 needles / cm 2 , and the penetration depth is 1.8 mm.

[0146] Example 6:

[0147] In this embodiment, the difference from Example 1 is that the treatment time in S2 is 5 min, and the electrostatic field strength is-30 kV; the needle density in S4 is 120 needles / cm 2 , and the penetration depth is 2.0 mm.

[0148] Example 7:

[0149] In this embodiment, the difference from Example 1 is that the treatment time in S2 is 7 min, and the electrostatic field strength is-20 kV; the needle density in S4 is 135 needles / cm2 , the penetration depth is 2.0 mm.

[0150] Example 8:

[0151] In this example, the difference from Example 1 is that the treatment time in S2 is 7 min, the electrostatic field strength is -25 kV; the needle density in S4 is 150 needles / cm 2 , the penetration depth is 1.6 mm.

[0152] Example 9:

[0153] In this example, the difference from Example 1 is that the treatment time in S2 is 7 min, the electrostatic field strength is -30 kV; the needle density in S4 is 120 needles / cm 2 , the penetration depth is 1.8 mm.

[0154] Comparative Example 1:

[0155] In this comparative example, the difference from Example 5 is that no ultrasonic cavitation and electrostatic field synergistic treatment is performed in S2.

[0156] Experimental Example 1:

[0157] The nuclear protective clothing prepared in Examples 1-9 and Comparative Example 1 is cut into 10 cm x 10 cm size samples, 5 parallel samples are taken from each group, and the following tests are performed.

[0158] 1. X-ray attenuation efficiency test: using an X-ray diffractometer, the sample is fixed on the test platform, the X-ray energy range is 30-100 keV, the transmission intensity of the sample at 30 keV, 40 keV, 50 keV, 60 keV, 70 keV, 80 keV, 90 keV and 100 keV is recorded, as well as the incident intensity without sample, the attenuation efficiency is calculated by formula (1-transmission intensity / incident intensity) x 100%; each sample is tested at each energy point for 3 times, the average value is taken, the minimum value and the maximum value of the attenuation efficiency of each sample (including the easy-to-sweat part and the other part, the area ratio of the easy-to-sweat part is 30%, and the area ratio of the other part is 70%) in the whole range of 30-100 keV are recorded as the attenuation efficiency range of the part; the minimum value and the maximum value of the attenuation efficiency of the easy-to-sweat part and the other part in the energy range of 30-100 keV are selected and multiplied by the area ratio to obtain the weighted average value, and the average attenuation efficiency of the whole protective clothing is obtained.

[0159] 2. Air permeability test: using digital air permeability tester, clamp the sample in the test cavity, set the test pressure difference to 200 Pa, the instrument automatically records the air volume through the sample within 1 min, calculates the air transmission per unit time, each sample is tested twice with a 10 s interval to balance the state.

[0160] 3. Water vapor transmission rate test: using constant temperature and humidity weighing method, take the moisture permeable cup (diameter 6 cm) and fill it with 20 g of anhydrous calcium chloride (particle size 2-5 mm), seal the sample to cover the cup opening (test area 28.26 cm²), place it in an environmental chamber with a temperature of 38 ℃ and a relative humidity of 90 %, weigh the moisture permeable cup after 24 h, calculate the water vapor transmission rate by the formula (total mass after moisture absorption-initial total mass) / test area. The air speed in the environmental chamber is kept at 0.5 m / s during the test.

[0161] 4. Elongation at break test: using a universal material testing machine, cut the sample into a 5 cm x 1 cm strip, clamp it in the upper and lower clamps (clamping distance 3 cm), set the tensile rate to 50 mm / min, record the elongation at break of the sample, calculate the elongation at break by the formula (elongation at break / initial clamping distance) x 100 %, test each sample 3 times, and take the average after removing outliers.

[0162] All test data is rounded to one decimal place, the mean and standard deviation of each group of samples are calculated to ensure data accuracy and repeatability, and the results are shown in the following table:

[0163] Table 1 Comparison of experimental results Table 1

[0164]

[0165] Table 2 Comparison of experimental results Table 2

[0166]

[0167] From the experimental results, it can be seen that Comparative Example 1, which was not treated by ultrasonic cavitation and electrostatic field, had an attenuation efficiency range of 73.0 % to 92.5 % in the perspiration-prone area, which was significantly lower than all the examples. This is because the untreated primary fibers have a tendency to agglomerate, resulting in uneven distribution of BWWT composite shielding particles (especially tungsten oxide and bismuth oxide) in the polypropylene matrix, forming local weak shielding areas. In the high-energy X-ray region (close to 100 keV), the penetration ability of the rays is enhanced, and the gaps between the agglomerates cannot provide effective shielding, resulting in a decrease in the lower limit of the attenuation efficiency to 73.0 %.

[0168] In contrast, the embodiments treated by the combination of ultrasonic cavitation and electrostatic field showed higher attenuation efficiency in the perspiration-prone areas. The attenuation efficiency of Example 1 treated by 40 kHz ultrasonic frequency and -20 kV electrostatic field intensity for 3 min increased to the range of 82.5% to 98.0%. This is because the impact force generated by the cavitation collapse of 40 kHz high-frequency ultrasound in deoxygenated anhydrous ethanol effectively breaks the higher-fragility tungsten oxide agglomerates, and the simultaneously applied electrostatic field makes the KH560-modified bismuth oxide particles surface positively charged, overcoming the agglomeration tendency through directional electrostatic repulsion, achieving uniform dispersion of particles in the matrix. This highly dispersed particle provides a continuous and weak area-free ray shielding path, thus showing stable and efficient attenuation ability in the full energy range of 30-100 keV.

[0169] Example 5 reached the peak of 86.5%-99.0% in the perspiration-prone areas by increasing the electrostatic field intensity to -25 kV and extending the treatment time to 5 min, while the air permeability (1350.6 mm / s) and water vapor permeability (2300.7 g / m 2 ·24 h) also achieved the best of the whole sample. This is because the highly dispersed particles achieve equivalent shielding at a lower areal density, and the micropores formed by the enrichment of carbon dioxide at the interface during supercritical carbon dioxide treatment are not easily blocked, thus forming more effective air permeation channels. In addition, the uniformly dispersed particles help to evenly transmit stress in the polypropylene matrix, combined with the enhanced interfacial bonding force of KH560 modification, the elongation at break is increased to 62.5%, the fiber toughness is good, and the internal structure is more uniform.

[0170] In addition, Comparative Example 1 was treated by needle punching, but due to the lack of ultrasonic cavitation and electrostatic field synergistic treatment of particle dispersion, the elongation at break was only 41.0%. While Example 4 used a combination of high density of 150 needles / cm 2 and a shallow depth of 1.6 mm, the fabric structure was tight, and both air permeability and elongation at break were low. While Example 5 used a combination of medium density of 135 needles / cm 2 and a relatively deep penetration depth of 1.8 mm, the fibers carrying tungsten carbide particles could more fully exert the mechanical anchoring effect of the angular structure, building a more stable and elastic network skeleton in three-dimensional space, achieving the highest elongation at break of 62.5%, and the stable support framework formed ensured that the integrity of the fabric after the subsequent supercritical carbon dioxide treatment to generate microporous structure would not be weakened, achieving high air permeability. Example 3 and Example 9 respectively used higher needle density (150 needles / cm 2) or a deeper penetration depth (2.0 mm), but the elongation at break was much lower than that of Example 5, because the pores in the fiber web were excessively squeezed, some of the connected pores became closed, and the flow path of gas and water vapor was blocked.

[0171] The above is based on the ideal embodiment of the present application, through the above description, the relevant personnel can make various changes and modifications without deviating from the scope of the technical idea of the present application. The technical scope of the present application is not limited to the content of the specification, and the technical scope must be determined according to the scope of claims.

Claims

1. A method for preparing a lightweight, lead-free, breathable nuclear protective suit, characterized in that, Includes the following steps: Step 1: BWWT composite shielding particles are blended with polypropylene to obtain masterbatch, and the masterbatch is modified and then melt-spun to form composite fibers. After combing and orientedly laying the composite fibers into a composite fiber web, needle punching and supercritical carbon dioxide treatment are performed to obtain 3D composite fiber needle-punched fabric; among them, the masterbatch is modified and melt-spun to obtain nascent fibers, and the nascent fibers are subjected to ultrasonic cavitation and electrostatic field synergistic treatment. The preparation method of the BWWT composite shielding particles includes dry mixing 55-65 wt% bismuth oxide, 10-20 wt% tungsten oxide, 10-20 wt% tungsten carbide and 5-15 wt% tantalum oxide at 750-850 rpm for 10-15 min to form BWWT composite shielding particles. The preparation method of the masterbatch includes melting and blending 30-40 wt% polypropylene and 60-70 wt% BWWT composite shielding particles in a temperature field of 165-190 ℃ and a rotation speed of 110-130 rpm for 3-5 min; after filtering to remove impurities with a diameter greater than 50 μm, extruding the melt into strips through a die with a diameter of 1-3 mm, passing it into a circulating water cooling tank at 22-28 ℃ for solidification, and finally cutting it into cylindrical masterbatch with a length of 1-6 mm and a diameter of 1-3 mm. The method for modifying the masterbatch includes adding the masterbatch to an anhydrous ethanol solution of KH560 silane coupling agent at pH 4.0-5.0 and a concentration of 1-3 wt%, and refluxing the reaction at 65-75℃ and a stirring speed of 180-220 rpm for 80-100 min; after the reaction, filtering, washing with anhydrous ethanol 3-5 times, and vacuum drying at 75-85℃ for 3-5 h to obtain the modified masterbatch; Step 2: Apply bismuth solution twice to the modified polyimide film and hot press to obtain a lightweight lead-free protective material; the preparation method of the modified polyimide film includes immersing the polyimide film in a 0.9-1.1 wt% KH550 silane coupling agent ethanol solution, treating it at 45-55℃ for 4.5-5.5 min, and then drying it with hot air at 75-85℃ for 9-11 min to obtain the modified polyimide film; Step 3: The 3D composite fiber needle-punched fabric and the lightweight lead-free protective material are connected by a sewing process to produce a nuclear protective suit; The ultrasonic cavitation and electrostatic field synergistic treatment involves treating the patient in an inert environment with an ultrasonic frequency of 38 to 42 kHz and an electrostatic field strength of -30 to -20 kV for 3 to 7 minutes, and the needle puncture treatment uses 120 needles / cm. 2 Up to 150 thorns / cm 2 The needle density and the insertion depth are 1.6 to 2.0 mm.

2. The preparation method according to claim 1, characterized in that, The preparation methods of 3D composite fiber needle-punched fabrics include: S1: BWWT composite shielding particles are melt-blended with polypropylene and extruded to obtain masterbatch; S2: After surface modification of the masterbatch, it is melt-spun to form nascent fibers. The nascent fibers are then subjected to ultrasonic cavitation and electrostatic field synergistic treatment, and after hot stretching and shaping, composite fibers are obtained. S3: After cutting the composite fibers to a fixed length, comb them into a single-layer fiber web, and then lay the single-layer fiber web in an oriented manner to obtain a composite fiber web; S4: The composite fiber web is subjected to air curtain guidance and needle punching to obtain a needle-punched fabric intermediate. S5: The preheated needle-punched fabric intermediate is subjected to gradient hot pressing and pressure holding cooling to obtain a compressed and shaped fabric. S6: The compressed and shaped fabric is treated with supercritical carbon dioxide and rapidly depressurized. After being rolled by hot rollers and cooled and shaped, a 3D composite fiber needle-punched fabric is obtained. The gradient hot pressing includes the following three consecutive pressure stages: The first stage applies a pressure of 0.4-0.6 MPa for 8-12 seconds; The second stage applies a pressure of 2.5-3.0 MPa for 17-23 seconds. The third stage applies a pressure of 5.0-6.0 MPa for 25-35 seconds.

3. The preparation method according to claim 2, characterized in that, The hot stretching and setting method involves introducing the nascent fibers, which have been treated by ultrasonic cavitation and electrostatic field, into an environment of 130-140℃, controlling the orientation and crystallization with a stretching ratio of 1.9-2.3, and setting them with a cooling roller at 22-28℃ to obtain composite fibers.

4. The preparation method according to claim 2, characterized in that, The method of fixed-length cutting involves cutting the composite fiber into fixed-length fiber bundles of 5.0 to 8.0 cm.

5. The preparation method according to claim 2, characterized in that, The single-layer fiber web has a unit area mass of 0.045 to 0.055 g / cm³. 2 .

6. The preparation method according to claim 1, characterized in that, The preparation method of lightweight lead-free protective material includes the following steps: M1: Modify the polyimide film to obtain a modified polyimide film; M2: A bismuth solution is coated onto a modified polyimide film to form a wet film, which is then subjected to hot pressing to obtain a composite film intermediate with a bismuth coating. M3: A bismuth solution is coated again on the surface of the composite film intermediate to form a wet film. After hot pressing, a composite film with a thickened bismuth coating is obtained. M4: The composite film is calendered and then cooled and shaped to obtain a lightweight lead-free protective material; The hot pressing process includes preheating at 265-275 ℃ and 0.05-0.2 MPa for 19-21 min, followed by pressing at 290-300 ℃ and 24-26 MPa for 14-16 min.

7. The preparation method according to claim 1, characterized in that, The suturing process includes the following steps: T1: Cut the 3D composite fiber needle-punched fabric and the lightweight lead-free protective material into pieces, then cut the pieces and spray them with a functional adhesive layer. T2: Sew the processed cut pieces together; T3: Apply hot melt adhesive tape to the seam and then pulse hot press to bond it; T4: Perform melt sealing at the joint.

8. A lightweight, lead-free, breathable nuclear protective suit, prepared by the method described in any one of claims 1-7, characterized in that, It includes areas prone to sweating and other areas, wherein the areas prone to sweating are made of 3D composite fiber needle-punched fabric, and the other areas are made of lightweight lead-free protective material.

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