Melt-processable impact-resistant fiber-reinforced composites

Abstract

This disclosure provides a fiber-reinforced composite material comprising a matrix of thermoplastic polyamide resin, at least 3% by weight of at least one impact modifier, and 7% to 60% by weight of discontinuous meta-aramid fibers as fiber reinforcement. The composite material is melt-processable and impact-resistant, exhibiting a value of at least 12 ft-lbs / in (640 J / m) as measured by the unnotched Izod test method according to ASTM D4812. This composite material can be used to manufacture articles, such as safety products.

Description

Technical Field

[0001] This disclosure relates to fiber-reinforced composite materials that are melt-processable and exhibit excellent impact properties, as well as articles made from such composite materials. Background Technology

[0002] A wide variety of composite materials have been used to prepare a wide variety of articles. A composite material (often simply called a "composite") is a material made of two or more constituent materials that have significantly different physical or chemical properties. When combined, they produce a material with properties different from the individual components. The individual components remain separate and distinct within the finished structure, distinguishing composite materials from mixtures and solid solutions. New materials may be preferred for many reasons. Common examples include materials that are stronger, lighter, or stiffer than conventional materials.

[0003] Examples of composite materials include reinforced concrete and masonry, composite wood such as plywood and fiberboard, reinforced plastics such as glass fiber reinforced nylon, ceramic matrix composites, and metal matrix composites. Summary of the Invention

[0004] This disclosure relates to fiber-reinforced composite materials that are melt-processable and exhibit excellent impact properties, as well as articles made from such composite materials.

[0005] In some embodiments, the composite material comprises a matrix comprising at least one thermoplastic polyamide resin; at least one impact modifier comprising at least 3% by weight based on the total weight of the composite material; and 7% to 60% by weight of fiber reinforcement based on the total weight of the composite material. The fiber reinforcement comprises discontinuous meta-aramid fibers. The composite material is melt-processable and impact-resistant, having a value of at least 12 ft-lbs / in (640 J / m) as measured by the unnotched Izod test method according to ASTM D4812.

[0006] Articles of manufacture are also disclosed. In some embodiments, the article comprises a fiber-reinforced composite material comprising a matrix comprising at least one thermoplastic polyamide resin; at least one impact modifier comprising at least 3% by weight based on the total weight of the composite material; and 7% to 60% by weight of fiber reinforcement based on the total weight of the composite material. The fiber reinforcement comprises discontinuous meta-aramid fibers. The composite material is melt-processable and impact-resistant, having a value of at least 12 ft-lbs / in (640 J / m) as measured by the unnotched Izod test method according to ASTM D4812. In some embodiments, the article comprises personal safety articles. These personal safety articles include helmets, protective face shields, face masks, safety glasses, electrically powered breathing apparatus or components thereof, self-contained breathing apparatus, air filters, filter housings, noise-canceling earmuffs, protective hoods, or protective hood inserts. Detailed Implementation

[0007] A wide variety of composite materials have been used to prepare a wide variety of articles. A composite material (often simply called a "composite") is a material made of two or more constituent materials that have significantly different physical or chemical properties. When combined, they produce a material with properties different from the individual components. The individual components remain separate and distinct within the finished structure, distinguishing composite materials from mixtures and solid solutions. New materials may be preferred for many reasons. Common examples include materials that are stronger, lighter, or stiffer than conventional materials.

[0008] Many composite materials are formed by creating a mesh of reinforcing material, surrounding the mesh with a curable matrix material, and curing the matrix to form the composite. Examples include reinforced concrete, where a mesh of metal bars (reinforcing bars) is formed, and then concrete is poured around the mesh and allowed to harden. Another example is FRP (fiber-reinforced polymer or fiber-reinforced plastic), where a fabric or web of reinforcing fibers (called a preform) is surrounded by a curable resin (such as a thermosetting epoxy), and the curable resin is then cured to form the composite. Fiber-reinforced composites are widely known and have been used industrially for a wide range of applications for over 40 years. Composites using continuous fibers in the form of tows or woven fabrics exhibit excellent mechanical properties and are often collectively referred to as continuous fiber composites.

[0009] While these types of composites are very useful, there is still a need for composites that do not use continuous fibers and in which the entire composite is melt-processable. Such composites are called discontinuous fiber composites and typically use synthetic fibers with a length of less than 25 mm. Discontinuous fiber composites can be formed into a wide variety of shapes, including highly flexible shapes, using common plastics processing techniques such as thermosetting injection molding or thermoplastic injection molding. Discontinuous fiber composites are known in the art and are widely used in a variety of applications. These include polyamide (nylon) thermoplastic resins reinforced with synthetic glass, ceramics, carbon, graphite, or aramid fibers. While discontinuous glass-reinforced and carbon fiber-reinforced nylons are known to have very good mechanical properties, discontinuous aramid-reinforced thermoplastic nylons have relatively poor mechanical properties such as tensile strength and impact strength. This contrasts directly with continuous aramid fiber composites and aramid woven fabrics, which exhibit excellent impact performance. In fact, continuous aramid composites made with thermosetting epoxy resins are known to even have ballistic protection against small-caliber firearms. Because these composites are lightweight and impact-resistant, they are used in a variety of aircraft and marine applications and typically contain glass or carbon fibers to form continuous blends. On the other hand, discontinuous aramid-reinforced thermoplastics are known to have properties opposite to those of continuous aramid fiber composites, exhibiting poor impact resistance and being particularly sensitive to notches.

[0010] Impact resistance is often a critical engineering design requirement and a product characteristic used in material selection during the engineering design phase. Depending on the end application, impact resistance can be measured using a variety of techniques. One test method frequently used by material manufacturers for plastics and composites is called the unnotched Izod impact test (according to ASTM D4812). In this test, a bar is struck under controlled conditions by an impact device, with one end held vertically in a vise. The energy required for the test bar to break is recorded. This test method is often used to compare two or more different materials under specific environmental conditions.

[0011] Despite their poor impact resistance, discontinuous aramid composites have been the subject of considerable effort due to their other desirable properties. Discontinuous aramid composites known in the art, such as short aramid fiber-reinforced nylon, offer an advantage over their glass-reinforced counterparts in excellent abrasion resistance. Consequently, they are commercially used for specialized applications such as sliding parts, gears, sprockets, pinions, etc. These composites are known to exhibit excellent abrasion resistance despite their poor impact performance, with impact strengths typically ranging from 9 ft-lbs / in to 10 ft-lbs / in as measured by unnotched Izod (ASTM D4812). Such discontinuous aramid fiber composites are available from various plastics compounding companies, including RTP Company, Celanese Inc., and DuPont Inc. Long fiber aramid nylon composites are also known in the art and are commercially available from Celanese Inc. Despite their relatively long fiber length (12 mm), these materials containing 35% wt% aramid fibers still exhibit low impact strength (10 ft-lbs / in). In contrast, commercially available long glass fiber composites containing 35% wt% fiber demonstrate excellent impact strength (16 ft-lbs / in to 20 ft-lbs / in). Due to their superior combination of impact resistance, stiffness, strength, and chemical resistance, glass-reinforced nylon has been one of the most widely used engineering materials over the past 45 years.

[0012] This paper presents a novel class of discontinuous aramid fiber composites exhibiting a variety of desirable and unexpected properties, including excellent impact resistance and hot melt processability. These composites possess unnotched Izod impact values ​​exceeding 33 ft-lbs / in., making them particularly suitable as engineering thermoplastics for a wide range of industrial, medical, and safety applications. Due to their superior impact resistance, the composites disclosed herein are particularly suitable as alternatives to conventional engineering thermoplastics such as nylon, glass-reinforced nylon, polycarbonate, acetal, and polyester. This paper discloses such composites comprising a nylon matrix, an impact modifier, and discontinuous meta-aramid fibers. The discontinuity of the fibers means that the fibers are dispersed within the matrix and have discrete lengths. Discontinuous fiber composites can be further classified as short fiber composites (fiber lengths of 1 mm or less) or long fiber composites (where the average fiber length is from 1 mm to 50 mm, typically about 12 mm before molding). It should be understood that discontinuous fiber composites typically have a fiber length distribution that depends on the initial starting fiber length during manufacturing and the molding conditions.

[0013] Meta-aromatic polyamide fibers are less well-known than para-aromatic polyamide fibers such as KEVLAR or poly(p-phenylene terephthalamide), and exhibit properties different from para-aromatic polyamides. Commercial meta-aromatic polyamide fibers are based on the polymer poly(p-phenylene isophthalamide). The difference in properties between meta-aromatic and para-aromatic polyamide fibers is a direct result of the different substitution sites on the phenylene ring of the polymer backbone. Meta-aromatic polyamide polymers have an inherent kink in their polymer backbone due to the fact that the sites substituted by meta-aromatic polyamide groups are at positions 1 and 3 on the phenylene ring, unlike the more linear para-aromatic polyamide polymers where the substituted sites are at positions 1 and 4. Meta-aromatic polyamide fibers are known to be significantly weaker than their para-aromatic polyamide counterparts, exhibiting lower crystallinity, lower glass transition temperature, and lower thermal stability. Furthermore, they have lower molecular orientation and tensile modulus. However, although meta-aramid fibers are at least four times weaker than para-aramid fibers, they remain relatively strong, exhibiting tensile strength similar to that of ordinary steel alloys (600 MPa to 800 MPa). Furthermore, unlike para-aramid fibers, meta-aramid fibers are considerably more ductile, possessing an elongation at break value exceeding 20% ​​compared to the 3% to 4% elongation of para-aramid fibers. While not wishing to be bound by theory, one of the benefits of using discontinuous meta-aramid fibers is believed to be their relative flexibility during melt processing and their ability to better maintain their fiber length (i.e., without breakage during processing) due to their lower stiffness and higher ductility. It is also believed that the composites disclosed herein are exceptionally tough due to the combination of better fiber adhesion of meta-aramid fibers to the specified nylon matrix polymer, the higher ductility of meta-aramid fibers, and the lower stiffness of the fibers. All these properties improve flexibility and impact resistance, allowing for a more uniform and widespread distribution of impact loads throughout the composite. The composite material disclosed herein also acts as a ductile material and can resist the application of large strains (>15%) without failing in a brittle manner. This provides another mechanism for increased energy absorption compared to conventional composite materials, such as glass fiber composites and para-aramid fiber composites, which fail at lower strains.

[0014] In some embodiments, the composite materials of this disclosure further comprise an interface modifier. It is believed that the interfacial adhesion between the meta-aramid fibers and the matrix nylon can be improved or optimized by adding an interface modifier to the composite material. In some embodiments, the composite materials of this disclosure exhibit exceptionally high impact strength by using an interface modifier in conjunction with discontinuous aramid fibers. Without being bound by theory, it is believed that certain interface modifiers can covalently bond to both the fiber surface and the nylon resin. The modifiers can also alter the surface energy of the reinforcing fibers and / or enhance hydrogen bonding forces. These modifiers may enhance similar or polar interactions at the fiber surface or even generate chain entanglement at the fiber surface.

[0015] The composites disclosed herein exhibit superior impact properties, significantly better than those of discontinuous aramid fiber thermoplastic composites known in the art. In some embodiments, the composites possess such high impact strength (e.g., unnotched Izod values ​​>34 ft-lbs / in) that they even outperform most commercially available short glass fiber reinforced nylon and short carbon fiber reinforced nylon. Therefore, the composites disclosed herein are particularly suitable as alternatives to these conventional short fiber composites comprising glass-reinforced nylon and glass-reinforced polyester. The substitution of glass-reinforced fibers is desirable because glass fibers can be abrasive and have a higher density. In contrast, the composites of this disclosure with discontinuous meta-aramid fibers are non-abrasive and have a lower density. Consequently, during manufacturing operations such as injection molding, the tool life of molds and screws containing the composites of this disclosure can be 10 to 20 times longer than that of glass-filled materials. This can have a significant impact on the cost per part over several years.

[0016] Furthermore, the composite material disclosed herein has a very low density. This is because it uses meta-aramid fibers (1.37 g / cc vs. 2.70 g / cc), which have a lower density compared to glass fibers. Due to its low density and high impact strength, the composite material disclosed herein is particularly suitable for lightweight applications, including automotive parts, aircraft parts, and components of safety products, including but not limited to respirators, helmets, fire safety products, goggles, and welding shields.

[0017] As previously mentioned, continuous fiber reinforced composites have long, typically continuous fibers that extend along the length of the manufactured part, thus providing strength and impact resistance. The use of discontinuous fibers is not expected to yield the superior strength properties, such as tensile or flexural strength, obtained with continuous fibers. However, it has been found that current composites using discontinuous meta-aramid fibers exhibit unexpectedly large improvements in impact resistance and ductility, and they also have lower densities.

[0018] Composite materials with discontinuous fibers can be prepared by mixing the discontinuous fibers with a thermoplastic matrix material. The composite materials can be prepared by compounding using various methods involving high or low shear mixing, such as twin-screw extruders or single-screw extruders. Additional discontinuous fibers, such as glass fibers, metal fibers, carbon fibers, and para-aramid fibers, may be included in the composite materials. Some fibers, especially relatively stiff glass fibers, can be abrasive to processing equipment and molds, and as mentioned earlier, this may be undesirable.

[0019] The use of personal safety products requires robust yet flexible composite materials. Examples include helmets, face shields, goggles, reusable respirators, etc. These products come in a wide range of shapes and are ideally lightweight. Impact resistance is particularly important for such products. Impact resistance is a measure of a material's resistance to mechanical impact without undergoing any physical change. Impact resistance can be measured in several ways. As previously mentioned, one test that has been found particularly useful in measuring impact resistance is the unnotched Izod test method according to ASTM D4812, as described in the Examples section. This test is widely used in the plastics industry and allows for direct comparison of two or more materials.

[0020] Unless otherwise specified, all figures used in the specification and claims to express structural dimensions, quantities, and physical properties should in all cases be understood to be modified by the term "about". Therefore, unless stated to the contrary, the numerical parameters listed in the foregoing specification and appended claims are approximations, which may vary according to the desired properties sought by a person skilled in the art using the teachings disclosed herein. Numerical ranges expressed in terms of endpoints include all numbers contained within that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5) and any range within that range.

[0021] Unless otherwise expressly stated, as used in this specification and the appended claims, the singular forms “a,” “an,” and “described” cover embodiments having multiple referents. For example, the reference to “a layer” covers embodiments having one layer, two layers, or more layers. Unless otherwise expressly stated, as used in this specification and the appended claims, the term “or” is generally used in a meaning that includes “and / or.”

[0022] The term "thermoplastic" is used in accordance with the definition commonly understood in the field of polymers, and refers to a plastic polymer material that becomes flexible or moldable at a certain elevated temperature and solidifies upon cooling. Unlike thermosetting materials, in which solidification is permanent, in thermoplastic materials, the cycle of heating to become flexible and solidifying upon cooling can be repeated multiple times.

[0023] As used herein, the term "polyamide" refers to polymers containing polyamide bonds. Polyamide is often used interchangeably with the term "nylon." The amide bond is of the following type: -(-R b -(CO)-NR a -R c -)-, where R b R is an alkylene or arylene group. a R is a hydrogen or alkyl group. c The alkylene or arylene groups are present, and (CO) is a carbonyl group -C=O. Polyamides (often also called nylon) are prepared by the condensation of a diamine and a diacid, or by the condensation of an amino acid containing both an amine and an acid functional group in a single molecule. The term "aromatic polyamide" as used herein refers to a polyamide containing at least 85% aryl groups linked by amide bonds.

[0024] The terms "room temperature" and "ambient temperature" are used interchangeably, referring to temperatures in the range of 20°C to 25°C.

[0025] The terms "Tg" and "glass transition temperature" are used interchangeably. If measured, unless otherwise specified, the Tg value is determined by differential scanning calorimetry (DSC) at a scan rate of 10 °C / min. Typically, the Tg value of the copolymer is not measured; instead, it is calculated using the well-known Fox formula, using the homopolymer Tg value provided by the monomer supplier, as understood by those skilled in the art.

[0026] As used herein, the term "adjacent" in the context of two floors means that the two floors are adjacent to each other and there is no intervening opening space between them. They may be in direct contact with each other (e.g., stacked together) or there may be an intervening floor.

[0027] As used herein, the terms “polymer” and “macromolecule” are consistent with their common usage in chemistry. Polymers and macromolecules are composed of many repeating subunits. As used herein, the term “macromolecule” is used to describe a group attached to a monomer having multiple repeating units. The term “polymer” is used to describe the material obtained by a polymerization reaction.

[0028] The term "alkyl" refers to a monovalent group that is an alkane group, where the alkane is a saturated hydrocarbon. Alkyl groups can be straight-chain, branched, cyclic, or combinations thereof, and typically have 1 to 20 carbon atoms. In some embodiments, the alkyl group contains 1 to 18, 1 to 12, 1 to 10, 1 to 8, 1 to 6, or 1 to 4 carbon atoms. Examples of alkyl groups include, but are not limited to, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, n-hexyl, cyclohexyl, n-heptyl, n-octyl, and ethylhexyl ester.

[0029] The term "aryl" refers to a monovalent group consisting of an aromatic ring and a carbocyclic ring. An aryl group can have one to five rings attached to or fused with an aromatic ring. Other ring structures can be aromatic, non-aromatic, or combinations thereof. Examples of aryl groups include, but are not limited to, phenyl, biphenyl, terphenyl, anthryl, naphthyl, acenaphthenic, anthraquinone, phenanthryl, anthracenyl, pyrene, peryl, and fluorenyl.

[0030] The term "alkanediol" refers to a divalent group that is a group of an alkane. Alkanediols can be straight-chain, branched, cyclic, or a combination thereof. Alkanediols typically have 1 to 20 carbon atoms. In some embodiments, alkanediols contain 1 to 18, 1 to 12, 1 to 10, 1 to 8, 1 to 6, or 1 to 4 carbon atoms. The group center of the alkanediol can be on the same carbon atom (i.e., an alkylidene group) or on different carbon atoms.

[0031] The term "arylene" refers to a divalent group that is both a carbocyclic and aromatic. This group has one to five rings, either linked, fused, or a combination thereof. Other rings may be aromatic, non-aromatic, or a combination thereof. In some embodiments, the arylene group has up to five rings, up to four rings, up to three rings, up to two rings, or one aromatic ring. For example, the arylene group may be phenylene.

[0032] The term "heteroalkylene" refers to a divalent group comprising at least two alkylene groups linked by a thio, oxygen, or -NR- group, wherein R is an alkyl group. Heteroalkylene groups can be straight-chain, branched, cyclic, substituted with alkyl groups, or combinations thereof. Some heteroalkylene compounds are polyoxyalkylenes, wherein the heteroatom is an oxygen atom, such as, for example...

[0033] -CH2CH2(OCH2CH2) n OCH2CH2-.

[0034] This document discloses composite materials. In some embodiments, the composite material comprises a matrix comprising at least one thermoplastic polyamide resin; at least one impact modifier, said impact modifier comprising at least 3% by weight, such as 3% to 35% by weight, based on the total weight of the composite material; and a discontinuous fiber reinforcement. The fiber reinforcement comprises discontinuous meta-aramid fibers, wherein the composite material is melt-processable and impact-resistant, having a value of at least 12 ft-lbs / in (640 J / m) as measured by the unnotched Izod test method according to ASTM D4812.

[0035] The composite material comprises a matrix containing at least one thermoplastic polyamide resin. A wide range of polyamide resins are suitable. It is believed that the matrix, as a polyamide resin, promotes compatibility with meta-aramid fiber reinforcing agents. Without being bound by theory, it is believed that the polyamide resin can hydrogen-bond with the surface of the aromatic polyamide fibers, thereby promoting adhesion. Additionally, it is believed that the high concentration of aromatic groups in the matrix nylon improves the miscibility of the fiber surface. In some embodiments, the thermoplastic polyamide resin is an aliphatic polyamide or a semi-aromatic polyamide. The thermoplastic polyamide can be a homopolymer or a copolymer. Mixtures and blends of thermoplastic polyamides can also be used.

[0036] Suitable polyamide materials can be described by repeating units of general formula 1:

[0037] -(-(CO)-A-(CO)-NR 1 -B-NR 1 -)-

[0038] Formula 1

[0039] Where A and B are independently alkylene, heteroalkylene, arylene, or arylene groups; (CO) is a carbonyl group C=O; and R 1 The carbon atoms are hydrogen atoms or alkyl groups. If at least one of A or B is an arylene alkyl or aryl group, the polyamide is described as semi-aromatic. Typically, groups A and B contain 1 to 20 carbon atoms and may contain one or more heteroatoms, typically oxygen, nitrogen, or sulfur. In some embodiments, groups A and B contain 1 to 15 carbon atoms or even 1 to 10 carbon atoms. In some embodiments, the polyamide is an AB-type copolymer, such as poly(hexyl adipate), also known as nylon 6,6.

[0040] Typically, polyamide polymers are prepared by the condensation reaction of a diacid (or its equivalent, such as an acyl halide) with a diamine, as shown in reaction scheme 1:

[0041] HO2C-A-CO2H+HR 1 NB-NR 1 H→-(-(CO)-A-(CO)-NR 1 -B-NR 1 -)-+H2O

[0042] Reaction Scheme 1

[0043] Among them, A, B, and R 1 As stated above.

[0044] A wide range of thermoplastic polyamide resins are suitable. These include commercially available nylons such as nylon 6, nylon 6,6, nylon 6,12, nylon 6,10, nylon 9T, nylon 6I (also known as poly(hexamethylene isophthalamide)), PPA, and high-temperature nylon (HTN) resins utilizing terephthalic acid or other aromatic acids as structural units. Furthermore, nylon blends constituting polyamides or copolyamides as the main polymeric component can be used. These blends may use polyesters, polypropylenes, or siloxane copolymers as minor components.

[0045] This composite material contains an impact modifier, which is an additive that improves the impact resistance of the base nylon polymer. It is worth noting that nylon itself is known as a tough material. The amount of impact modifier used in a particular composition typically depends on the intended end-use application of the composition. The impact modifier can be a soft or rigid material, but is generally a compromise with a material that is elastic and forms discrete, phase-separated regions in the nylon matrix, typically with diameters of about 0.2 to 3.0 micrometers. This morphology significantly enhances the energy absorption capacity of the host polymer using known mechanisms of increased shear yielding, cracking, and possible cavitation in the host polymer. This can be achieved by using a variety of polymeric additive materials as impact modifiers, including but not limited to maleated olefin elastomers, core-shell particles, grafted block copolymers, epoxy-modified polymers, elastomer copolymers, ethylene terpolymers, ionomers, and modified butadiene copolymers including core-shell particles. The use of impact modifiers for nylon resins is known in the art. Particularly suitable impact modifiers are core-shell particles and maleated elastomers. Commercially available examples of impact modifiers include PARALOID EXL 2335 and EXL 2314 (MBS core-shell modifiers) from Dow Chemical and ROYALTUF 485 and ROYALTUF 527 from Addivant. In the composite compositions disclosed herein, one or more impact modifiers can be used to enhance the impact resistance of the composite. It is believed that in some compositions containing aliphatic nylon, the impact modifier plays a secondary role by improving adhesion to the fibers. Core-shell particles are particularly useful impact modifiers because they do not require high-shear mixing to achieve the desired morphology and particle size. Typically, impact modifiers are used at levels of at least 3% to up to 35% by weight, and more typically 8% to 25% by weight, based on the total weight of the composite. In addition to improving impact properties, impact modifiers can also improve the ductility of the composite at lower temperatures by altering the ductile / brittle transition. The overall role of the impact modifiers in the composites disclosed herein is to alter the nylon matrix and promote yielding. This is particularly evident in the composites described below, as they are exceptionally ductile even under complex stress conditions at strains exceeding 20%. Consequently, when formulated to optimal levels, the compositions described herein are exceptionally tough and virtually unbreakable, especially after allowing molded parts to reach near-equilibrium moisture content.

[0046] The composite material also contains a fiber reinforcement, which is a discontinuous meta-aromatic polyamide fiber. Meta-aromatic polyamide fibers are aromatic polyamides having amide bonds at the 1,3 positions of the aromatic ring. The general structure of well-known meta-aromatic polyamides (also known as poly(m-phenylene isophthalamide)) is shown in general formula 2. Meta-aromatic polyamide fibers having this polymer structure are available, for example, from DuPont (NOMEX) and Teijin Corporation (TEIJINCONEX). In this document, meta-aromatic polyamide fibers are defined as polyamide fibers in which at least 85% of the amides are linked to aromatic groups in the polymer backbone, and at least 25% of the amide groups contain meta-aromatic bonds. As mentioned above, poly(m-phenylene isophthalamide) is a well-known meta-aromatic polyamide fiber containing all meta-bonds. According to this disclosure, fibers prepared from aromatic copolyamides containing both meta-aramid and para-aramid bonds can be useful, provided they contain sufficient meta bonds to satisfy the above definition of a meta-aramid fiber. Commercially available meta-aramid fibers suitable for the composites of this disclosure include NOMEX fibers from DuPont, TEIJINCONEX fibers from Teijin Aramid (part of Teijin Ltd.), and ARAWIN fibers from Toray Advanced Materials Korea Inc. Fibers suitable for use in this disclosure typically have a diameter of 10 to 25 micrometers and their cross-sectional shape can be non-circular or elliptical. It is desirable that the fibers be completely intact and free from fibrillation. While fibrillation can increase surface area, this morphological characteristic is undesirable and can increase the viscosity of the thermoplastic composite in the melt during processing. The use of fibrillated aromatic polyamide fibers is taught, for example, in European Patent Publication 3,401,355.

[0047]

[0048] The fibers in the composite materials of this disclosure are discontinuous, meaning they are discrete fibers with defined lengths. The fiber length is typically 50 mm or less. However, for certain processes such as compression molding, longer fibers with lengths from 50 mm to 62 mm can be used. Two general categories of fibers exist suitable for the melt-processable composite materials of this disclosure. The first general category is typically “long” fibers with a length greater than 1 mm, generally from 1 mm to 50 mm, or even from 1 mm to 20 mm. The second general category is “short” fibers with a length less than 1 mm.

[0049] The fiber reinforcement comprises at least meta-aramid fibers and may also include other fibers. In some embodiments, the fiber reinforcement further includes carbon fibers. Carbon fibers are typically present as a minor component of the fiber reinforcement, meaning that they are present at less than 50% by weight of the total weight of the fiber reinforcement. However, for structural parts, it may be useful for carbon fibers to be at higher levels, such as 60% to 75% by weight of the total weight of the fiber reinforcement. In some embodiments, the composite material disclosed herein is a hybrid composite of meta-aramid fibers and carbon fibers with excellent impact properties and low density. Compared to meta-aramid fiber reinforcement alone, these hybrid materials using both meta-aramid and carbon fibers offer increased beneficial properties, including: higher thermal flexural temperature (HDT); higher stiffness; and higher flexural and compressive strength. Such composite materials have an overall excellent balance of mechanical properties while still maintaining excellent impact resistance, with unnotched Izod impact values ​​exceeding 25 ft-lbs / in. Furthermore, for a given application, the mechanical properties and density can be “tuned” by adjusting the percentage of meta-aramid fibers and carbon fibers in the composition. Because hybrid composites incorporating carbon fibers exhibit a good overall balance of desired properties such as solvent resistance, low density, high impact resistance, high strength, high stiffness, excellent abrasion resistance, and high temperature resistance (>100°C), they are commercially viable for a wide range of applications, including moving and stationary parts. Examples include machine parts, levers, tools, screws, gears, conveyor parts, textile machinery parts, agricultural and processing equipment, chemical and fluid pumps, automotive parts, aerospace parts, engine parts, cooling system parts, off-road vehicles, sporting goods applications, bolts, threaded assemblies, household and commercial appliances, precision machinery parts, and marine applications. These materials are also particularly suitable for a wide range of safety and engineering applications. A non-limiting example is engineering materials that use aluminum and cast magnesium alloys to replace lightweight parts. These hybrid fiber-reinforced nylon composites are also particularly useful as alternatives to traditional glass-reinforced nylon, which is widely used in many industries for the production of molded parts. In some embodiments, the hybrid composites may utilize fibers of different lengths. For example, a combination of short carbon fibers with long meta-aramid fibers may be used, or different combinations may be used, such as short carbon fibers with short aramid fibers. The latter can be used to injection mold very thin wall portions or very delicate features in molded parts. In another embodiment, the composite material may also contain flame retardants as described below. Such composite materials can be used in electrical, electronic, and fire-resistant applications.

[0050] In some embodiments, in addition to meta-aramid fibers, the fiber reinforcing agent may also include synthetic fibers other than carbon fibers. These fibers include e-glass fibers, s-glass fibers, α-glass fibers, graphite fibers, boron fibers, metal fibers, other aramid fibers, stainless steel fibers, and ceramic fibers. The combination of meta-aramid fibers and glass fibers is particularly suitable because they are low in cost, easy to process, and offer a balance of properties.

[0051] A wide range of fiber loadings are applicable to the composite materials of this disclosure. In some embodiments, the fiber reinforcement is present at a loading of 7% to 60% by weight, and in some embodiments, 10% to 50% by weight, based on the total weight of the composite composition.

[0052] In addition to the thermoplastic polyamide resin, impact modifier, and fiber reinforcement described above, the composite material may contain other optional additives. Optional additives may enhance the desired properties or provide additional desired properties. Examples of suitable optional additives include flame retardants, interface modifiers, or combinations thereof.

[0053] In some embodiments, at least one flame retardant is added to the composite material. A wide range of flame retardants are suitable, including halogenated and non-halogenated flame retardants. One particularly suitable class of flame retardant additives is phosphorus-containing flame retardants, including metal phosphines and red phosphorus. Another useful class is brominated polymer flame retardants. Red phosphorus is a particularly desirable flame retardant because it is effective in nylon composite compositions at relatively low levels. In particular, red phosphorus can be an effective flame retardant in nylon composites at levels of about 7% by weight. Because less than 10% by weight of red phosphorus can be used, it is expected that red phosphorus will not significantly adversely affect impact performance. Other flame retardants require higher levels to be effective, typically 20% to 25% by weight, and these higher levels are expected to adversely affect the impact performance or other desired properties of the composite material.

[0054] A wide range of interface modifiers are suitable for use in the composites included in this disclosure. Interface modifiers can play a variety of roles in these composites. These roles include increasing and / or optimizing fiber-matrix adhesion, reducing melt viscosity, reducing molding stress, reducing interfacial tension and melt viscosity, and improving stress transfer to the fibers and / or impact-modifying phases. Many of these roles are used to improve impact properties. Some interface modifiers can also be used as fiber reinforcing agents and compatibilizers for thermoplastic polyamide matrices. A wide range of interface modifiers can be suitable, including low molecular weight functional organic compounds, copolymers, and polymers containing reactive groups. Examples of suitable interface modifiers include maleated polyolefin copolymers, long-chain alcohols, long-chain fatty acids, epoxy polymers and oligomer resins, semi-aromatic nylon copolymers, block copolymers, zirconates, titanates, organosiloxane agents, and combinations thereof. The latter three are particularly useful for modifying the surface of synthetic reinforcing fibers. Semi-aromatic nylon copolymers and polymers can be useful because they can contain segments with solubility parameters similar to meta-aromatic polyamide fibers and improve adhesion through hydrogen bonding and polar interactions. Furthermore, at high temperatures, they can entangle with the bulk nylon matrix and undergo amide exchange reactions. Therefore, they interact and improve adhesion between the fiber and the matrix. Maleated polymers such as maleated polyolefins, maleated olefin copolymers, and epoxy-functionalized polymers are particularly useful because they can chemically react with the nylon matrix and / or fiber reinforcing agents. This serves both to covalently graft polymer chains onto a specified material phase and to provide a means of generating or improving chemical compatibility. Such surface modification at the fiber interface involves generating polar functional groups (including amide bonds) that can enhance interfacial adhesion through hydrogen bonding and / or other polar forces (i.e., dipole interactions) and improve adhesion through polymer grafting. Polymer chains covalently attached to a material phase such as the fiber surface are freely entangled, interact, and / or crystallized with polymer chains in the nylon matrix phase or impact modifier phase.

[0055] Other suitable additives and modifiers that can be used in the composite materials of this disclosure include fillers, lubricants, processing aids, moisture scavengers, chain extenders, heat stabilizers, UV absorbers and stabilizers, corrosion inhibitors, antioxidants, metal salts, colorants, nucleating agents, carbon black, glass bulbs, ceramic powders, fluoropolymers, and plasticizers. It is important to note that some materials can be multifunctional, i.e., providing more than one function. For example, long-chain alcohols and long-chain acids can be used as both lubricants and interface modifiers.

[0056] The composite material disclosed herein can be prepared by a variety of techniques. Typically, the material is prepared in a two-step process. In the first step, thermoplastic granules are prepared. In the second step, the thermoplastic granules are dried and then used to produce articles by methods known in the art, such as injection molding, rotational molding, or compression molding.

[0057] Thermoplastic granules can be prepared using a variety of techniques with low or high shear methods. A particularly suitable method for preparing short-fiber meta-aramid composites uses conventional plastic compounding with a twin-screw extruder. In this method, the thermoplastic polyamide resin and impact modifier, and optionally an interface modifier, are first mixed at the beginning of the barrel, and in a later part of the process, fiber reinforcement is introduced at the end of the barrel to minimize fiber breakage and prevent fibrillation. The molten material is then cooled and granulated to form granules of discrete length. These granules can then be stored, transported, or set aside for later use. The granules can be used to form various articles through a second step as described below.

[0058] This composite material can also be prepared in a one-step process: thermoplastic polyamide resin, impact modifier, fiber reinforcement, and optional additives are hot-melt mixed, and then the melt is directly injected into a hot mold. Various hot-melt mixing techniques using a variety of hot-melt mixing equipment are suitable. Both batch and continuous mixing equipment can be used. Examples of batch methods include methods using BRABENDER (e.g., the BRABENDERPREP CENTER, commercially available from CW Brabender Instruments, Inc., South Hackensack, NJ) or BANBURY internal mixing and roll forming equipment (e.g., equipment available from Farrel Co., Ansonia, CT). Examples of continuous methods include single-screw extrusion, twin-screw extrusion, disc extrusion, reciprocating single-screw extrusion, and pin-barrel single-screw extrusion. Continuous methods may employ dispensing elements, pin mixing elements, static mixing elements, and dispersing elements such as MADDOCK mixing elements and SAXTON mixing elements.

[0059] In some embodiments, the compositions of this disclosure are prepared in granular form using a two-step method. The granules can be prepared using known techniques of the plastics compounding industry, including formulation using a twin-screw extruder with chopped fibers and other components to produce the short-fiber composites described above. Alternatively, in other embodiments, long-fiber granules can be manufactured using a fiber pultrusion method, commercially used to manufacture long carbon fiber and long glass fiber granules. In this method, fiber bundles are drawn under pressure through a heated polymer melt using specialized equipment, and the resulting fully impregnated fiber bundles are cut to specific lengths to form cylindrical granules. Thus, the fiber length is the same as the length of the granules. Using this method, long-fiber granules comprising meta-aramid fibers with customized fiber lengths from 3 mm to 60 mm can be manufactured. Pultrusion is a highly desirable process for manufacturing the granules of this disclosure because the fibers themselves are not damaged and only low shear forces are used during the process for a short time (typically less than 25 seconds). The granules can then be processed in a second step using various known techniques to manufacture articles and molded articles. Suitable melt processing techniques for processing long fiber pellets include injection molding and compression molding.

[0060] Injection molding is a very useful technique for producing molded articles from the composite material granules of this disclosure. Injection molding is perhaps the most widely used technique in the world for producing molded plastic articles and parts. The composite materials of this disclosure can be processed in a manner similar to that of commercially available glass-reinforced nylon. Prior to molding, the resin granules are typically dried to a moisture content of 0.14% by weight or less. Generally, molding is performed using medium to fast injection speeds and high injection rates and high molding temperatures (60°C to 150°C), as well as sufficient holding pressure and time, to minimize voids in the molded part. The compositions of this disclosure can also be used for overmolding or insert molding in combination with plastics, other polymer composites, foams, metals, and elastomers.

[0061] Other melt processing methods can be used to manufacture molded parts having the composite material granules of this disclosure, including compression molding, rotational molding, overmolding, extrusion, and 3D printing. The compositions of this disclosure can also be melt-processed into filaments.

[0062] Because the composite material of the present invention is malleable at room temperature, molding processes can also be used to produce articles. The term "molding" is used to refer to the re-forming of nylon composite preforms under pressure. For example, the nylon 6,6-based composite material of this disclosure can be re-formed using a simple molding process at temperatures of 180°C to 200°C and pressures of 16,000 psi to 20,000 psi. Molding can result in a degree of strength and toughness that cannot be achieved by melt processing.

[0063] Articles prepared from the above-described composite material are also disclosed. In some embodiments, the article comprises a fiber-reinforced composite material comprising a matrix comprising at least one thermoplastic polyamide resin; at least one impact modifier comprising at least 3% by weight based on the total weight of the composite material; and a fiber reinforcing agent comprising at least 7% by weight based on the total weight of the composite material. The fiber reinforcing agent comprises discontinuous meta-aramid fibers. The composite material is melt-processable and impact-resistant, having a value of at least 12 ft-lbs / in (640 J / m) as measured by the unnotched Izod test method according to ASTM D4812.

[0064] The matrix, impact modifier, and fiber reinforcement have been described in detail above. In some embodiments, the matrix comprises aliphatic polyamide or semi-aromatic polyamide. The impact modifier can be a soft or rigid material, but typically comprises a rubbery material and forms discrete, phase-separated regions with a diameter of about 0.2 micrometers to 3.0 micrometers. The size and shape of these regions in the composite sample can vary. The fiber reinforcement comprises meta-aramid fibers (long fibers) with a length of 1 mm to 50 mm, more typically 1 mm to 20 mm, meta-aramid fibers (short fibers) with a length of less than 1 mm, mixtures thereof, and may also include other fibers such as carbon fibers, glass fibers, or other synthetic fibers as described above. Furthermore, in some embodiments, the composite material also comprises at least one additive, said additive including a flame retardant, an interface modifier selected from maleated polyolefin copolymers, long-chain alcohols, long-chain fatty acids, epoxy polymers and oligomer resins, semi-aromatic nylon copolymers, block copolymers, zirconates, titanates, organosiloxane agents, or combinations thereof. In some embodiments, the fiber reinforcement is present at a loading of 7% to 60% by weight, or 10% to 50% by weight, based on the total weight of the composite composition.

[0065] Composite materials can be used to manufacture a wide range of articles. In some embodiments, the articles include personal safety articles selected from head protection articles, face protection articles, goggles, or combinations thereof. Examples of suitable personal safety articles include helmets, protective face shields or welding articles, face masks, safety glasses, electric self-contained breathing apparatus or components of electric self-contained breathing apparatus, self-contained breathing apparatus, air filters, filter housings, noise-canceling earmuffs, protective covers or protective cover inserts. Suitable components may include turbine housings, fan blades, battery housings, battery packs, buckles, clamps, valve bodies, air conditioner parts, pipes, threaded connections, valves, blower parts, housings, etc.

[0066] Example

[0067] These examples are for illustrative purposes only and are not intended to limit the scope of the appended claims. Unless otherwise specified, all parts, percentages, ratios, etc., in the examples and the remainder of the specification are by weight. Unless otherwise specified, all solvents and other reagents used were obtained from Sigma-Aldrich Chemical Company (Milwaukee, Wisconsin). The following abbreviations are used: mm = millimeter; m = meter; ft = foot; in = inch; RPM = revolutions per minute; psi = pound per square inch; lb = pound; J = joule; min = minute; hr = hour; RH = relative humidity. The terms "% by weight," "% by weight," and "wt%" are used interchangeably.

[0068] Abbreviation Table

[0069]

[0070] Test methods

[0071] Unobstructed Izod Impact Test

[0072] Prepare the test bars as described below and perform the unnotched Izod test according to ASTM D4812. Test values ​​are measured in J / m (joules per meter) and converted to the more commonly used ft-lbs / in (ft-lbs / in) value. Report the average of the two test bars using two sets of units.

[0073] Flammability test

[0074] The test rod was prepared as described below and its flammability was tested according to Underwriters Laboratories (UL).

[0075] Extensibility test

[0076] Test bars are prepared as described below, and ductility is tested by bending the test bars to an angle 20° above the yield point of the composite material. If the test bar can bend to an angle greater than 30° and has permanent deformation, indicating that the composite test bar is ductile (>10% strain), the result is listed as "yes".

[0077] Example

[0078] Preparation of molding materials .

[0079] All examples were prepared by mixing pre-cut fibers (7 mm to 10 mm in length) into the polymer melt at 100 rpm using a conical intermittent twin-screw mixing unit, with a total mixing time of 3 to 4 minutes. The composite resin was prepared by slowly adding the polymer and additives into the mixing chamber over a 2-minute mixing time to produce a homogeneous melt phase. After 2 minutes of mixing, discontinuous fibers were added over a short period and mixed with the polymer melt under high shear for 55 to 70 seconds. For samples containing carbon fibers, the carbon fibers were introduced into the melt first, followed by the meta-aramid fibers. The polymer melt temperature for all Nylon-2 (Nylon 9T) samples was 318 °C, and the polymer melt temperature for all impact-modified Nylon-1 (Nylon 6,6) samples was 300 °C. Following high-shear mixing, the polymer melt was injected into a heated mold at 280 psi for a 20-second residence time to produce composite test bars (127 mm × 12.5 mm × 3.2 mm). The mold temperature for Nylon-2 (Nylon 9T) samples was 130°C, and the mold temperature for all Nylon-1 (Nylon 6,6) samples was 102°C. Unless otherwise specified, the samples were then removed from the mold and conditioned at room temperature and 50% RH for 2 weeks prior to testing.

[0080] Example 1 and Comparative Examples C1-C3

[0081] Sample test bars were prepared using nylon-1 with 23 wt% MA fibers and 2 wt% interface-1, according to the method described above. Comparative sample results using the same test methods for commercially available fiber-reinforced materials are shown in Table 1. The unnotched Izod test was performed on the sample test bars and reported in Table 1. These data are from samples aged for 2 weeks at room temperature and 50% humidity.

[0082] Table 1

[0083] Example Material Specifications supplier Unobstructed Izod ft-lbs / in(J / m) E-1 23% MA fiber and 2% interface-1 ---- 24.9(1,330) C-1 Nylon 6,6 containing 20% ​​aramid Antep Company 10.0(534) C-2 IM Nylon 6,6 containing 20% ​​glass fiber Antep Company 19.0(1,010) C-3 IM Nylon 6,6 containing 30% glass fiber Antep Company 21.0(1,120)

[0084] Example 2

[0085] Two separate test bars were molded separately as described above, having the following composition: Nylon-2 (56 wt%); MA fiber (22 wt%);

[0086] FR-1 (22 wt%). The flammability of two rods was tested according to the flammability test given above. The results for both samples were V-0. Bending one test rod to an angle exceeding the yield point of the composite material by 30° indicates that the composite test rod is ductile (>10% strain) and has permanent deformation. Compared with the test rod without meta-aramid fibers, the test rod showed significantly greater stiffness.

[0087] Example 3

[0088] Test bars with two different levels of FR-2 were prepared as described above. Flammability and bending test data are shown in Table 2 below.

[0089] Table 2

[0090]

[0091] Example 4

[0092] Test bars were molded using the following composition: Nylon-1 (67 wt%); Impact Modifier-1 (3 wt%); and MA fibers (30 wt%). The MA fibers were dried in a vacuum oven at 75°C for 4 hours prior to compounding. Impact Modifier-1 was added as an impact modifier but could also be used as an interface modifier and impact modifier. The test bars were aged at room temperature and atmospheric conditions for 4 weeks. Bending the test bars to a 90° angle in a metal fixture demonstrated that the composite material was extremely ductile (>25% strain) and did not fail in a brittle manner.

[0093] Example 5 .

[0094] Two test bars were molded using the following composition: Nylon-1 (72 wt%); Interface-2 (1 wt%); and MA fiber (27 wt%). The interface modifier, docosyl alcohol, was also used as a lubricant. After 2 weeks of aging, the average unnotched Izod impact strength was 23.7 ft-lbs / in (1,265 J / m).

[0095] Example 6 .

[0096] This example demonstrates the excellent impact resistance of the hybrid composite material. Two test bars were molded using the following composition: Nylon-2 (72 wt%), carbon fiber (14 wt%), and MA fiber (14 wt%). The test bars were equilibrated at room temperature and approximately 50% humidity for 3 months. One test bar was manually bent by bending it at a 90° angle, resulting in permanent ductile deformation. This indicates that the material can reach strain levels >20% without failing in a brittle manner and exhibits ductile behavior. When these molded test bars were aged for 12 months and tested according to ASTM D4812, the average unnotched impact value was 36.2 ft-lbs / in (1,932 J / m).

[0097] Example 7 .

[0098] Test bars were prepared using the following composition: nylon-2 (45 wt%); FR-2 (15 wt%); and MA fibers (40 wt%). Compared to Example 1, this test bar exhibited significantly higher flexural stiffness and also demonstrated ductile behavior without failure when bent at a 60° angle. The average unnotched Izod value was 39.2 ft-lbs / in (2,092 J / m) during impact testing. This example demonstrates that composites with higher fiber loading exhibit excellent impact resistance.

[0099] Example 8 .

[0100] Four test bars (two for each composition) were prepared using the following two compositions. Composition 1 comprised: Nylon-1 (73 wt%); Interface-1 (2 wt%); and MA fibers (27 wt%). Composition 2 was identical to Composition 1 with 27 wt% MA fibers but without the interface modifier. The compositions were tested by manual bending at angles exceeding 90° after 6 months of conditioning at room temperature. Both compositions were exceptionally ductile and could bend at high strain (>20%) without failure, resulting in permanent deformation. Compared to Composition 1, Composition 2 exhibited visually greater stress whitening on the tensile side of the flexural portion. After 12 months of aging, both compositions were tested according to ASTM D4812 and showed unnotched Izod impact values ​​of >41.8 ft-lbs / in (2,231 J / m), with none of the test bars breaking during testing. This example demonstrates that the compositions according to this disclosure possess superior ductility and impact resistance, far exceeding any known discontinuous fiber thermoplastic composites, including long glass fiber nylon composites. This embodiment also demonstrates that these materials exhibit very high impact strength after aging under real-world conditions. It is well known that nylon 6,6 has a relatively high equilibrium moisture content, and its impact performance improves with increasing moisture content.

[0101] Example 9 .

[0102] A test rod was prepared using the following composition: nylon-2 (37 wt%); FR-1 (17 wt%), MA fiber (30 wt%), and carbon fiber (16 wt%). Due to the high fiber content, the test rod is exceptionally rigid.

Claims

1. A composite material, the composite material comprising: The matrix comprises at least one thermoplastic polyamide resin; At least one impact modifier, said impact modifier comprising at least 3% by weight based on the total weight of the composite material; and Based on the total weight of the composite material, 7% to 60% by weight of fiber reinforcement, wherein the fiber reinforcement comprises discontinuous meta-aramid fibers; and wherein the composite material is melt-processable and impact-resistant, having a value of at least 640 J / m as measured by the unnotched Izod test method according to ASTM D4812, and wherein the fiber reinforcement comprises a copolymer of poly(m-phenylene isophthalamide) or poly(m-phenylene isophthalamide).

2. The composite material according to claim 1, wherein the matrix comprises aliphatic polyamide or semi-aromatic polyamide.

3. The composite material according to claim 1, wherein the fiber reinforcing agent comprises meta-aramid fibers with a length of 1 mm to 50 mm.

4. The composite material according to claim 1, wherein the fiber reinforcing agent further comprises at least one other type of fiber, said other type of fiber being selected from carbon fiber, boron fiber, e-glass fiber, s-glass fiber, α-glass fiber, metal fiber, ceramic fiber, graphite fiber, and combinations thereof.

5. The composite material according to claim 1, wherein the composite material further comprises at least one additive, wherein the additive comprises a flame retardant or an interface modifier, the interface modifier being selected from maleated polyolefins, long-chain alcohols, epoxy polymers, zirconates, titanates, organosiloxane agents, and combinations thereof.

6. The composite material according to claim 5, wherein the composite material comprises a flame retardant additive, wherein the flame retardant additive contains phosphorus.

7. The composite material according to claim 1, wherein the meta-aramid fiber reinforcing agent is present at a loading of 10% to 50% by weight based on the total weight of the composite material.

8. The composite material according to claim 1, wherein the thermoplastic polyamide resin comprises nylon 6, nylon 6,6 or nylon 9T.

9. An article made of fiber-reinforced composite material, the article comprising: Fiber-reinforced composite material, the fiber-reinforced composite material comprising: The matrix comprises at least one thermoplastic polyamide resin; At least one impact modifier, wherein the at least one impact modifier accounts for at least 3% by weight based on the total weight of the composite material; as well as Based on the total weight of the composite material, 7% to 60% by weight of fiber reinforcing agent, wherein the fiber reinforcing agent comprises discontinuous meta-aramid fibers; Furthermore, the composite material is melt-processable and impact-resistant, having a value of at least 640 J / m as measured by the unnotched Izod test method according to ASTM D4812, and the fiber reinforcement comprises a copolymer of poly(m-phenylene isophthalamide) or poly(m-phenylene isophthalamide).

10. The article of claim 9, wherein the matrix comprises aliphatic polyamide or semi-aromatic polyamide.

11. The article of claim 9, wherein the fiber reinforcing agent comprises meta-aramid fibers with a length of 1 mm to 50 mm.

12. The article of claim 9, wherein the composite material further comprises at least one additive, wherein the additive comprises a flame retardant, an interface modifier, the interface modifier being selected from maleated polyolefin copolymers, long-chain alcohols, long-chain fatty acids, epoxy polymers, semi-aromatic nylon copolymers, block copolymers, zirconates, titanates, organosiloxane agents, and combinations thereof.

13. The article of claim 9, wherein the fiber reinforcing agent is present at a loading of 10% to 50% by weight based on the total weight of the composite material.

14. The article of claim 9, wherein the article comprises a personal safety article selected from head protection articles, face protection articles, goggles, or combinations thereof.

15. The article of claim 14, wherein the personal safety article comprises a helmet, a protective face mask or welded article, safety glasses, an electric air respirator or a component of an electric air respirator, a self-contained breathing apparatus, an air filter, a filter housing, noise-canceling earmuffs, a protective shield or a protective shield insert.

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