WO2015130376A2

WO2015130376A2 - Ballistic composite article

Info

Publication number: WO2015130376A2
Application number: PCT/US2014/069220
Authority: WO
Inventors: Jeffrey Alan Hanks; William George Kampert; Bryan Benedict Sauer; Soonjoo Son
Original assignee: E. I. Du Pont De Nemours And Company
Priority date: 2013-12-16
Filing date: 2014-12-09
Publication date: 2015-09-03
Also published as: WO2015130376A3

Abstract

Rigid ballistic composite articles are disclosed, the articles comprising a consolidated fabric section comprising two or more fibrous fabric layers and a resin binder layer disposed between at least some of the fabric layers, the resin binder layer comprising a thermoplastic material and a particulate filler comprising nano-silica, nano-clay, micropulp, or mixtures thereof; wherein a) the particulate filler has an average particle size of less than 500 nm in at least one dimension; b) the resin binder layer as a resin binder film has an initial tensile modulus in the range of about 40 MPa to about 1000 MPa measured at 20 °C; and c) the resin binder layer is present in the consolidated fabric section in an amount from about 8 weight percent to about 15 weight percent, based on the total weight of the resin binder layer and the fibrous fabric layers.

Description

^"RILE

Bailistic Composite Article

This application claims priority under 35 U.S.C. §1 19(e) from, and claims the benefit of, U.S. Provisional Application No. 81/918303 filed December 16, 2013, which is by this reference incorporated in its entirety as a part hereof for all purposes.

Rigid ballistic composite articles comprising a consolidated fabric section comprising two or more fibrous fabric layers and a resin binder layer disposed between at least some of the fabric layers are provided. The resin binder layer comprises a thermoplastic material and a particulate filler comprising nano-silica, nano-clay, micropuip, or mixtures thereof.

BACKGROUND

Ballistic articles such as bulletproof vests, helmets, tactical plates, structural members of helicopters, vehicle armor, and other military equipment containing high strength fibers are known. Fibers

conventionally used include aramid fibers such as poly(phenyienediamine terephthaiamide), glass fibers, nylon fibers, and ceramic fibers. For many applications, such as vests or parts of vests, the fibers are used in a woven or knitted fabric. The fibers may be encapsulated or embedded in a matrix material.

Poorly bonding resins such as phenolic or modified polyester can be added to high strain ballistic fabrics in order to form composites in which the resin does little more than keep out water. Often a nonbonding rubber latex is added to enhance nonbonding to the high strain, high tenacity fiber (such as Keviar®), in order that the high strain fiber breaks free of the composite matrix under impact and goes into tension along its length immediately, thus carrying the impact load over as large an area as possible. The stopping power of the ballistic fabric stack is thereby increased. Ideally, if the matrix material had about the same or faster elastic response properties to high velocity impact (ballistic) as the high strain fiber, the impact load would be absorbed by both the matrix material and by the high strain fiber simultaneously and the load would be distributed laterally over the widest area to the greatest extent. The matrix material would then absorb part of the load and also facilitate transfer of the load from fiber to fiber, resulting in improved ballistic performance.

Published patent application US 201 1 /0Ί 13534 A1 discloses an impact resistant composite article comprising two or more fibrous fabric layers and a polymeric layer disposed between at least some of the fabric layers, in which the peel strength measured at 20 °C between the fabric layer and the polymeric layer after pressing under specified conditions is less than 1 kg/cm, and where the weight percent of polymeric resin relative to the resin plus fabric is between 8% and 15%. The polymeric layer comprises a material selected from the group consisting of a thermoplastic material, a blend of thermoplastic materials, a thermosetting materiai, and a blend of thermosetting materials, and where the polymeric layer does not contain a thermoplastic materiai and a thermosetting materiai.

Published patent application US 201 1/01 17351 A1 discloses an impact resistant composite article comprising two or more stacks of fibrous fabric layers, the layers may comprise a repeilant treatment on the fibers, and an ionomer layer disposed between at least some of the fabric layers.

Published patent application WO 97/49546 discloses an antibaliistic shaped part comprising a stack of composite layers which are not linked to one another, each composite layer comprising two or more monolayers of unidirecfionaliy oriented fibers in a matrix, the fibers in each monolayer being at an angle to the fibers in an adjoining monolayer. Preferably, the e!astomeric matrix material in the shaped part comprises a thermoplastic elastomer having a modulus in tension (determined in accordance with ASTM D838, at 25 °C) of less than 40 MPa. !n a special embodiment, the matrix in the shaped part also contains, in addition to the elastomeric matrix material, a filler in an amount of from 5 to 80% by volume.

There is a continuing need for rigid ballistic composites and articles comprising such composites which can provide protection against projectile threats while also providing blunt trauma protection upon impact. There is a continuing need for ballistic composites which provide comparable or improved ballistic protection while being more cost effective than conventional ballistic composites. Moreover, lower weight ballistic composites and articles comprising the composites are desired.

SUGARY

Described herein are ballistic composite articles which can be used to provide protection to the body or to property. In one embodiment, a rigid ballistic composite article is provided, the article comprising:

a consolidated fabric section comprising two or more fibrous fabric layers and a resin binder layer disposed between at least some of the fabric layers, the resin binder layer comprising a thermoplastic material and a particulate filler comprising nano-silica, nano-clay, micropulp, or mixtures thereof;

wherein

a) the particulate filler has an average particle size of less than 500 nm in at least one dimension;

b) the resin binder layer as a resin binder film has an initial tensile modulus in the range of about 40 MPa to about 1000 MPa measured at 20 °C; and

c) the resin binder layer is present in the consolidated fabric

section in an amount from about 8 weight percent to about 15 weight percent, based on the total weight of the resin binder layer and the fibrous fabric layers.

!n one embodiment, at least one fibrous fabric layer comprises a polymer comprising aramid, ultra-high molecular weight high density polyethylene, ultra-high molecular weight high density polypropylene, polyvinyl alcohol, poiyazoie, or combinations or blends thereof. In one embodiment, the consolidated fabric section comprises ten or more fibrous fabric layers. In one embodiment, a thermally pressed stiff panel comprising the composite article is provided. In one embodiment, a helmet comprising the

composite article is provided. The ballistic composite articles disclosed herein are described with reference to the following figures.

Figure 1 provides a graphical representation of the correlation of higher initial tensile modulus of the resin binder layer, as a resin binder film, of the consolidated fabric section of the composite article with higher V50 above 3100 ft/s (945 m/s) for the composite article for Examples 10 and 1 1 .

Figure 2 provides a graphical representation of the correlation of higher initial tensile modulus of the resin binder layer, as a resin binder film, of the consolidated fabric section of the composite article with higher V50 for the composite article for Examples 1 and 4.

DETAsLED DESGRsPTlOIN

Definitions

The ballistic composite articles disclosed herein are described with reference to the following terms.

As used herein, where the indefinite article "a" or "an" is used with respect to a statement or description of the presence of a step in a process of this invention, it is to be understood, unless the statement or description explicitly provides to the contrary, that the use of such indefinite article does not limit the presence of the step in the process to one in number.

As used herein, when an amount, concentration, or other value or parameter is given as either a range, preferred range, or a list of upper preferable values and lower preferable values, this is to be understood as specifically disclosing all ranges formed from any pair of any upper range limit or preferred value and any lower range limit or preferred value, regardless of whether ranges are separately disclosed. Where a range of numerical values is recited herein, unless otherwise stated, the range is intended to include the endpoints thereof, and ail integers and fractions within the range. It is not intended that the scope of the invention be limited to the specific values recited when defining a range. The term "composite article", as used herein, refers to an article that comprises at least two components (i.e. a fabric layer and a resin binder layer) with significantly different physical or chemical properties and which remain separate and distinct on a macroscopic level within the finished structure. By "composite article" is meant any type of

construction, such as a panel, whether flat or otherwise, and formed or molded products, such as a helmet. The term "composite article" also includes but is not limited to laminates, multilayer structures, matrices, or variants thereof.

The term "strike face" as used herein refers to the surface of the armor that faces the ballistic threat or is otherwise intended to be struck first by a projectile.

The term "backface" as used herein refers to the surface of the armor that is worn toward the body or property to be protected.

The term "backface deformation" as used herein refers to the depression depth in the backing material resulting from a non-penetrating projectile impact. Backface deformation is measured from the plane defined by the front edge of the backing material fixture. The term "back face deformation" is synonymous with the terms "backface signature" and "trauma signature" used in the art.

The terms "fibrous fabric" and "fabric", as used herein, are synonymous and refer to a multilayer construction of fibers.

The term "fiber" as used herein refers to an elongate body the length dimension of which is much greater than the transverse dimensions of width and thickness. Accordingly, the term fiber includes monofilament fiber, multifilament fiber, ribbon, strip, a plurality of any one or

combinations thereof and the like having regular or irregular cross-section.

The term "thermoplastic" as used herein refers to polymers that undergo a transition from solid state to fluid state when heated and freeze to a glass or semi-crystalline state when cooled sufficiently. Thermoplastic polymers can be re-melted and re-molded.

The term "semi-crystalline" as used herein refers to the partial crystal! inity in a polymer characterized by a melting point upon heating whereby the polymer becomes more fluid, followed by a crystallization point upon cooling whereby it solidifies as the crystals reform. As used herein, the term "semi-crystalline acid ethylene copolymer" refers to a subset of the above semi-crystalline polymers where the ethylene sequences are able to crystallize in the acid ethylene copolymer.

The term "particulate filler" as used herein refers to a particle with discrete dimensions and having an average particle size of less than about 500 nm in at least one dimension that is incorporated in a polymer matrix. Particulate fillers differ from continuous fibers that are several inches long and comprise some fibrous based ballistic layers.

Disclosed herein are rigid ballistic composite articles comprising a consolidated fabric section comprising two or more fibrous fabric layers and a resin binder layer disposed between at least some of the fabric layers. Consolidation to join layers together and make a stiff panel takes place at high temperatures and pressures such as temperature of 130 °C (286 °F) to 180 °C (320 °F), and pressures of about 8.9 MPa (1000 psi) to 27.6 MPa (4000 psi). The resin binder layer comprises a thermoplastic material and a particulate filler comprising nano-siiica, nano-clay, rnicropulp, or mixtures thereof, the particulate filler having an average particle size of less than 500 nm in at least one dimension. The resin binder layer as a resin binder film has an initial tensile modulus in the range of about 40 MPa to about 1000 MPa measured at 20 °C. The resin binder layer is present in the consolidated fabric section of the composite article in an amount from about 8 weight percent (wt%) to about 15 wt%, based on the total weight of the resin binder layer and the fibrous fabric layers. The composite articles disclosed herein can be used to make thermally pressed stiff panels and helmets, for example, and can provide protection against projectile threats while also providing blunt trauma protection upon impact.

The ballistic composite article comprises a consolidated fabric section comprising two or more fibrous fabric layers that can be woven or nonwoven. As used herein, the term "woven" is meant to include any fabric that can be made by weaving; that is, by interlacing or interweaving at least two yarns, typically at right angles - but also using any

conventional orientation of the weave. Generally such fabrics are made by interlacing one set of yarns, called warp yarns, with another set of yarns, cailed weft or fill yarns. The woven fabric can have essentially any weave, such as plain weave, crowfoot weave, basket weave, satin weave, twill weave, and unbalanced. As used herein, the term "nonwoven" includes a unidirectional fabric, a multi-axial fabric, or a three-dimensional fabric. The multi-axial fabric can have layers of yarn oriented at an angle with respect to adjacent !ayer(s), and these layers can comprise

unidirectional arrays of yarns. The three-dimensional fabrics can also comprise unidirectional arrays of yarns. In one embodiment, at least one of the fibrous fabric layers comprises a woven fabric. In some

embodiments, at least one of the fibrous fabric layers comprises a non- woven fabric. In some embodiments, at least one of the fibrous fabric layers comprises a unidirectional fabric. As used herein, the term

"unidirectional fabric" refers to a fabric having reinforcing fibers in only one direction.

Suitable fibrous fabric layers can be prepared from fibers or tape made from a polymer such as a polyolefin (for example ultra-high molecular weight high density polyethylene [UHMWPE] or polypropylene [UHMWPP]), po!yaramid such as poiy(paraphenylene terephthalamide) sold by E.l. du Pont de Nemours and Company, Wilmington, DE Under the trade name KEVLAR®, polyvinyl alcohol), po!ybenzimidazoles, poiyareneazoles, and polypyridazoles such as polypyridobisimidazole, sometimes known as 5®. Combinations or blends of fibers can also be used, including mixtures of fibers made of different polymers or blends of different polymers in one fiber. Selection of the fiber type to be used is based on the ballistic properties required of the composite article. Suitable fibers have a tenacity at least about 900 MPa according to ASTM D-885 in order to provide superior ballistic penetration resistance. Suitable fibers typically also have a tensile modulus of at least about 10 GPa.

In one embodiment, a fibrous fabric layer comprises UHMWPE fibers. U.S. Patent No. 4,457,985 generally discusses oriented ultra-high molecular weight polyethylene and polypropylene fibers. Polyethylene fibers suitable for use in the composites disclosed herein are highly oriented fibers of weight average molecular weight of at least about 500,000 g/^'mol, for example at least about one million, or between about two million and about six million. Known as extended chain polyethylene (ECPE) fibers, such fibers may be produced from polyethylene solution spinning processes described, for example, in U.S. Patent No. 4,137,394 or U.S. Patent No. 4,356,138.

As used herein, the term "polyethylene" refers to a predominantly linear polyethylene material that may contain minor amounts of chain branching or comonomers not exceeding 5 modifying units per 100 main chain carbon atoms, and that may also contain not more than about 25 wt% of one or more polymeric additives such as a!kene-1 -polymers, for example low density polyethylene, polypropylene or poiybutylene;

copolymers containing mono-o!efins as primary monomers; oxidized poiyoiefins; graft poiyoiefin copolymers and polyoxymethylenes; or low molecular weight additives such as anti-oxidants, lubricants, ultra-violet screening agents, and colorants.

Depending upon the fiber-forming technique, the draw ratio and temperatures, and other conditions, a variety of properties can be imparted to these fibers. The tenacity of the fibers is ordinarily at least about 15 grams/ denier, for example at least about 20 grams/denier, or at least about 30 grams/denier, or at least about 40 grams/denier. Similarly, the tensile modulus of the fibers, as measured by an Instron tensile testing machine, is ordinarily at least about 300 grams/denier, for example at least about 500 grams/denier, or at least about 1 ,000 grams/denier, or at least about 1 ,500 grams/denier. These highest values for tensile modulus and tenacity are generally obtainable only by employing solution spun or gel fiber processes. In addition, many ECPE fibers have melting points higher than the melting point of the polymer from which they were formed. Thus, for example, whereas ultra-high molecular weight poiyethylenes of

500,000, one million and two million generally have melting points in the bulk of 134° C, the ECPE fibers made of these materials have melting points of 145 °C or higher. The increase in melting point reflects a higher crystalline orientation of the fibers as compared to the bulk polymer.

Ballistic composite articles having improved performance can be formed when polyethylene fibers having a weight average molecular weight of at least about 500,000, a modulus of at least about 500 and a tenacity of at least about 15 g/denier are employed. See, for example, John V. E. Hansen and Roy C. Laible, "Flexible Body Armor Materials," Fiber Frontiers ACS Conference, June 10-12, 1974.

!n one embodiment, a fibrous fabric layer comprises ultra high molecular weight polypropylene fibers which are highly oriented and have a weight average molecular weight at least about 750,000, for example at least about one million, or at least about two million. Methods for forming ultra high molecular weight polypropylene into reasonably highly oriented fibers are known in the art and are disclosed, for example in US Patent No. 4,358,138 and US Patent No. 4,413,1 10. Since polypropylene is a much less crystalline material than polyethylene and contains pendant methyl groups, tenacity values achievable with polypropylene are generally substantially lower than the corresponding values for

polyethylene. Accordingly, a suitable tenacity is at least about 8

grams/denier, for example at least about 1 1 grams/denier. The tensile modulus for polypropylene is at least about 180 grams/denier, for example at least about 200 grams/denier. The melting point of the polypropylene is generally raised several degrees by the orientation process, such that the polypropylene fiber preferably has a main melting point of at least about 188° C, for example at least about 170° C.

In one embodiment, a fibrous fabric layer comprises poiyararnid fiber. Poiyararnid fiber is formed principally from aromatic po!yamide.

Suitable aromatic poiyamide fibers have a modulus of at least about 400 g/denier and tenacity of at least about 18 grams/denier. For example, poiy(phenylenediamine terephthalamide) fibers produced commercially by

E. I. du Pont de Nemours & Company under the trade names of Kevlar®

29 and Kevlar® 49 and having moderately high moduli and tenacity values are particularly useful in forming ballistic resistant composites. (Kevlar® 29 has 500 g/denier and 22 g/denier and Kevlar® 49 has 1000 g/denier and 22 g/denier as values of modulus and tenacity, respectively). Also useful in forming ballistic resistant composites is Kevlar© KM2. In some embodiments, at least one fibrous fabric layer comprises a woven fabric comprising po!y(p~phenylene terephthalamide) fiber.

In one embodiment, a fibrous fabric layer comprises polyvinyl alcohol fibers. Polyvinyl alcohol (PV-OH) fibers suitable for use in the ballistic compsite articles disclosed herein have a weight average molecular weight of at least about 500,000, for example at least about 750,000, or between about 1 ,000,000 and about 4,000,000, or between about 1 ,500,000 and about 2,500,000. Suitable PV-OH fibers typically have a modulus of at least about 160 grams/denier, for example at least about 200 grams/denier, or at least about 300 grams/denier, and a tenacity of at least about 7 grams/denier, for example at least about 10 grams/denier, or at least about 14 grams/denier, or at least about 17 grams/denier. PV-OH fibers having a weight average molecular weight of at least about 500,000, a tenacity of at least about 200 grams/denier and a modulus of at least about 10 grams/denier are particularly useful in producing ballistic resistant composites. PV-OH fibers having such properties can be produced, for example, by the process disclosed in US Patent No. 4,599,287.

In some embodiments, a fibrous fabric layer comprises poiyazole fiber, for example polyarenazoles such as polybenzazoles and

polypyridazoles, including homopolymers and copolymers. Additives can be used with the polyazoies, and up to about 10 wt% of other polymeric material can be blended with the polyazoies. Method for making suitable poiyazole homopolymers and copolymers are known in the art. Useful polybenzazoles include poiybenzimidazoies.for example poly(p-phenyiene benzobisoxazole and poiy(p-phenylene-2,8-benzobisoxazoie),

poiybenzothiazoles, and polybenzoxazoies, in particular such polymers that can form fibers having yam tenacities of 30 grams/denier or greater.

Useful polypyridazoles include polypyridimidazoles, po!ypyridothiazoies, and polypyridoxazoies, in particular such polymers that can form fibers having yarn tenacities of 30 grams/denier or greater. In some

embodiments, the polypyridazo!e is a poiypyridobisazole, for example poiy(1 _!4-(2,5-dihydiOxy)phenyiene-2_!8-pyndo[2,3-d:5,6-d^,]bisimidazole. Methods for making suitable polypyridazoles are known in the art.

The fibrous fabric layers may also contain one or more layers of high strength, polyolefin fiber composites such as the cross-plied unidirectional polyethylene fiber composite Dyneema® HB26 from DSM Co. (Netherlands) or highly oriented polyethylene films such as Tensylon® from DuPont. These oriented films are sometime called drawn tapes. In some embodiments, a first fibrous fabric layer comprises a first polymer, and a second fibrous fabric layer comprises a second polymer, and the first and second polymers are different. For example, in one embodiment a fibrous fabric layer comprises polyaramid fiber and another fibrous fabric layer comprises ultra high molecular weight polyethylene or polypropylene fiber. For unidirectional polyethylene fiber composites and Keviar® fabrics the fibers are continuous and can span the entire length.

In some embodiments, at least one fibrous fabric layer comprises a polymer comprising aramid, ultra-high molecular weight high density polyethylene, ultra-high molecular weight high density polypropylene, polyvinyl alcohol, poiyazoie, or combinations or blends thereof.

The fibrous fabric layers may also comprise hybrid fibers, for example, aramid and carbon hybrid fibers; aramid and glass hybrid fibers; aramid, carbon, and glass hybrid fibers; or carbon, glass, and extended chain polyethylene hybrid fibers. Hybridization of the fibers not only reduces costs, but in many instances improves the performance in armor structures. It is known that aramid fiber and carbon are significantly lighter than glass fiber. The specific modulus of elasticity of aramid is nearly twice that of glass, while a typical high tensile strength-grade of carbon fiber is more than three times as stiff as glass in a composite. However, aramid fiber has a lower compressive strength than either carbon or glass, while carbon is not as impact resistant as aramid. Therefore, a hybrid of the two materials results in a composite that is (1 ) lighter than a

comparable glass fiber-reinforced plastic; (2) higher in modulus, compressive strength and fiexurai strength than an ali-aramid composite; and (3) higher in impact resistance and fracture toughness than an all- carbon composite.

The fibrous fabric iayers can optionally be finished to provide repellency, for example as disclosed in published patent application US 201 1/01 13534 A1 . As used herein, the term "repeiiant material" refers to a hydrophobic material applied to a fabric that as a dry and very thin coating around individual fibers, resists wetting by aqueous media. For example, the fibrous fabric layer can be lightly coated with a fiuorinated material comprising fluorine and carbon atoms. In one embodiment, the fabric can be lightly coated with a fiuorinated material selected from the group consisting of Zonyi® D fabric fluoridizer consisting of fiuorinated

methacrylate copolymers, or Zonyl® 8300 fabric protector consisting of fiuorinated acrylate copolymers. The finish treatment of fabrics with such fiuorinated polymers and oligomers is known in the art and is not limited to these fiuorinated materials.

The ballistic composite articles disclosed herein comprise a consolidated fabric section comprising a resin binder layer disposed between at least some of the two or more fibrous fabric layers, the resin binder layer comprising a thermoplastic material and a particulate filler comprising nano-siiica, nano-ciay, micropulp, or mixtures thereof. The resin binder layer as a resin binder film has an initial tensile modulus in the range of about 40 MPa to about 1000 MPa measured at 20 °C according to ASTM D882. As used herein, the term "as a resin binder film" means the resin binder layer is in the form of a fiber-free thermally pressed film of

0.02 inch (0.051 cm) thickness. Methods for preparing a resin binder layer as a resin binder film are provided in the Experimental section herein. In some embodiments, the resin binder layer as a resin binder film has an initial tensile modulus in the range of about 40 MPa to about 800 MPa, or about 40 MPa to about 850 MPa, or about 100 MPa to about 650 MPa, or about 100 MPa to about 450 MPa. In some embodiments, the resin binder layer as a resin binder film has an initial tensile modulus between and optionally including any two of the following values: 40, 80, 100, 150, 200, 250, 300, 350, 400, 450, 500, 550, 600, 650, 700, 750, 800, 850, 900, 950, and 1000 MPa. Initial tensile modulus can be determined as described in the Experimental section herein.

As used herein, the term "unfilled resin binder layer" refers to a resin binder layer which contains only a thermoplastic material and no particulate filler. As used herein, the term "as an unfilled resin binder film" means the unfilled resin binder layer is in the form of a fiber-free thermally pressed film of 0.02 inch (0.051 cm) thickness. Methods for preparing an unfilled resin binder layer as an unfilled resin binder film are provided in the Experimental section herein.

In the composite articles disclosed herein, the resin binder layer can be present in an amount from about 8 wt% to about 15 wt%, based on the total weight of the resin binder layer and the fibrous fabric layers. In some embodiments, the resin binder layer is present in the composite article in an amount between and optionally including any two of the following values: 8 wt%, 9 wt%, 10 wt%, 1 1 wt%, 12 wt%, 13 wt%, 14 wt%, and 15 wt%, based on the total weight of the resin binder layer and the fibrous fabric layers. Suitable resin binder layers comprise

thermoplastic materials including, for example, a semi-crystalline acid ethylene copolymer, a polyurethane, a linear low density polyethylene, or combinations thereof. As used herein, the term "semi-crystalline acid ethylene copolymer" includes not only semi-crystalline acid ethylene copolymers with cation neutralization but also those without cation neutralization.

In one embodiment, the resin binder layer comprises a semi- crystalline acid ethylene copolymer, which is also referred to as an ionomer. As used herein, the term "ionomer" means a resin comprising ionicaily crossiinked ethyiene-methacryiic acid and ethylene-acryiic acid copolymers which can be at least partially neutralized by inorganic cations. Properties which distinguish these ionomer resins from other poiyoiefin heat-seal polymers are tear resistance, abrasion resistance, solid-state toughness and resistance to oil-fat permeation. A very wide variety of partially neutralized ionomer resins are manufactured by E.I. du Pont de Nemours and Company under the registered trademark SURLYN© or by Dow as RIMACOR". Suitable ethylene copolymers comprise about 9 wt% to 25 wt% acid comonomer.

In one embodiment, the thermoplastic material comprises an acid ethylene copolymer, wherein the ethylene copolymer is neutralized with an ion as disclosed in published patent application US 201 1/01 13534, which is herein incorporated by reference. To produce the ionomers, the parent acid copolymers are neutralized by at least between 30% and about 120%, based on the total number of equivalents of carboxy!ic acid moieties. At high neutralization levels above 80%, the ionomers are not melt extrudable if they are dry. Upon neutralization, the ionomers have one or more metallic cations. Metallic ions that are suitable cations may be monovalent, divalent, trivalent, multivalent, or mixtures thereof. Useful monovalent metallic ions include, but are not limited to, ions of sodium, potassium, lithium, silver, mercury, copper, and mixtures thereof. Useful divalent metallic ions include, but are not limited to, ions of beryllium, magnesium, calcium, strontium, barium, copper, cadmium, mercury, tin, lead, iron, cobalt, nickel, zinc, and mixtures thereof. Useful trivalent metallic ions include, but are not limited to, ions of aluminum, scandium, iron, yttrium, and mixtures thereof. Useful multivalent metallic ions include, but are not limited to, ions of titanium, zirconium, hafnium, vanadium, tantalum, tungsten, chromium, cerium, iron, and mixtures thereof. If is noted that when the metallic ion is multivalent, complexing agents, such as stearate, o!eate, salicylate, and phenoiate radicals may be included, as disclosed within U.S. Patent No. 3,404,134. The metallic ions used herein are preferably monovalent or divalent metallic ions. In one embodiment, the metallic ions used herein are selected from the group consisting of ions of sodium, lithium, magnesium, zinc and mixtures thereof. The parent acid copolymers may be neutralized as disclosed in U.S. Pat. No. 3,404,134.

The ionomers used herein may optionally contain other unsaturated comonomers. Examples of suitable unsaturated comonomers include, but are not limited to, methyl acrylate, methyl methacryiate, ethyl acryiate, ethyl rnetbacrylate, isopropyl acrylate, isopropyl rnethacrylate, butyl acrylate, butyl rnethacrylate and mixtures thereof. In general, the ionomers used herein may optionally contain up to about 20 wt%, or about 30 wt%, or about 50 wt% of other unsaturated comonomer(s) in addition to the ethylene and acid comonomers, based on the total weight of the copolymer.

In some embodiments, the resin binder layer comprises a thermoplastic material, wherein the thermoplastic material comprises a polyurethane. Useful polyurethanes include but are not limited to low modulus aliphatic polyester or poiyether soft segment polymers and low modulus aromatic polyester or poiyether soft segment polymers, which are known in the art. See, for example, Polyurethane Elastomers; Elsevier, Applied Science: Amsterdam, 1992 and Handbook of Polyurethanes; CRC Press: Boca Raton, FL, 1999. Useful polyurethanes can be prepared by methods known in the art or obtained commercially.

In one embodiment, the resin binder layer comprises a

thermoplastic material, wherein the thermoplastic material comprises a linear low density polyethylene or low melting ethylene copolymer such as ethyiene-octene, ethylene-vinyl acetate, or other low crystaiiinity

copolymers that are more flexible than polypropylene or high density polyethylene. In one embodiment, the thermoplastic material comprises a linear low density polyethylene.

The resin binder layer comprises a thermoplastic material and a particulate filler comprising nano-silica, nano-clay, micropuip, or mixtures thereof. Suitable particulate fillers have an average particle size of less than about 500 nm in at least one dimension. In some embodiments, the particulate fillers have an average particle size of less than about 400 nm in at least one dimension, for example less than about 300 nm, or less than about 200 nm, or less than about 100 nm, or less than about 50 nm, or less than about 30 nm, or less than about 20 nm, or less than about 10 nm. In some embodiments the particulate filler has an average particle size of from about 0.9 nm to about 200 nm in at least one dimension, for example from about 0.9 nm to about 150, or from about 0.9 nm to about 100 nm, or from about 0.9 nm to about 50 nm. In some embodiments, the particulate filler has an average particle size of less than about 100 nm in at least one dimension. In some embodiments, the particulate filler has an average particle size of less than about 30 nm in at least one dimension. The average particle size can be measured, for example using optical microscopy, transmission electron spectroscopy, or atomic force

microscopy. The particulate filler may be of any shape or mixture of shapes, for example spherical, platelet, rod-like, needle-like, or irregular. The particulate filler may be naturally occurring or synthetic material, or mixtures of these.

It is known that micro-particles, generally defined as particles having an average particle size in the range of about 500 nm to about 100,000 nm, and nano-particies, generally defined as particles having an average particle size in the range of 1 nm to 500 nm, when used as fillers in polymer resins, can have different effects on the modulus of the resin. It is known that due to the high surface area of nano-particies, the modulus of a filled resin can increase rapidly when the nano-particles are present at low weight percentages relative to the resin fraction. In contrast, micro- particles have lower surface area, and it is known that micro-particles need to be present at much higher weight percentages than nano-particles to substantially increase the modulus of the resin. This increase in modulus can give rise to a rapid drop in toughness, as indicated by the lower % elongation in film tensile studies for Examples 1 , 4, 7, 9, 10, and 1 1 in Table 1 . The increase in modulus, in turn, can lead to a surprising improvement in the ballistic penetration resistance of aramid fabrics coated with resin binder layers containing nano-particles, even though the resin binder layer becomes less tough when incorporating the nano- particles. While not wishing to be bound by theory, it is believed that a resin binder layer having lower toughness can facilitate the engagement and stretching of the aramid fibers upon impact of a ballistic projectile, which is necessary for the aramid fabric to provide penetration resistance. The resin binder layer itself cannot contribute directly to penetration resistance because the aramid fibers are hundreds of times stronger. Using nano-particles in the resin binder layer can be advantageous due to the lower weight percentages needed, thus offsetting the high density of the nano-particles themselves, and can reduce the total weight of the composite.

In some embodiments, the particulate filler comprises nano-silica. The term "nano-silica" as used herein means Si0₂ particles having an average particle size in the range of about 10 nm to 100 nm, for example about 10 nm to about 75 nm. Exemplary nano-sized silicas include but are not limited to fumed silica, coiioidai silica, fused silica, and silicates. In some instances, nano-silica particles are produced or provided in the form of a colloidal suspension in a liquid. Nano-siiica is available from various commercial sources and in various particle sizes. For example, Ludox© TM-40 (manufactured by W. R. Grace and Co.) is an anionic colloidal silica dispersion containing approximately 22-nm diameter silica particles with sodium cations, at 40 wt.% in H₂0 with a pH of 9; Ludox® TMA-40 (manufactured by W. R. Grace and Co.) is a deionized colloidal silica dispersion containing approximately 22-nm diameter silica particles at 34 wt.% in H₂0 with a pH of 4-7; and Ludox® CL (manufactured by VV. R. Grace and Co.) is a cationic coiioidai silica dispersion containing approximately 22~nm diameter silica particles that have been surface- treated with alumina, at 30 wt.% in H₂0 with a pH of 4.5.

In some embodiments, the particulate filler comprises nano-clay.

The term "nano-clay" as used herein refers to nanometer scale, layered magnesium aluminum silicates which are typically in the form of platelets about 1 nanometer thick and about 70-150 nanometers across. Suitable nano-clays include smectite (e.g., aluminum silicate smectite), hectorite, fluorohectorite, montmorilionite (e.g., sodium montmorilionite, magnesium montmorilionite, and calcium montmorilionite), bentonite, beideiite, saponite, stevensite, sauconite, nontronite, iliite, and mixtures of two or more thereof. Suitable nano-clays also include layered silicates obtained from micas or clays, or from a combination of micas and clays.

Representative examples of such layered silicates include, without limitation, pyrophillite, talc, muscovite, phlogopite, iepidolithe, zinnwaldite, rnargarite, hydromuscovite, hydrophlogopite, sericite, nontronite, vermiculite, sudoite, pennine, kiinoch!or, kaolinite, dickite, nakrite, antigorite, hailoysiie, allophone, palygorskite, and synthetic forms thereof. Nano-clays are available from various commercial sources and in various particle sizes. For example, Cloisite® Na+ is an unmodified, naturally occurring montmorilionite clay having a cation exchange capacity (CEC) of about 92 meq/100 g and available from Southern Clay Products division of Rockwood Additives, Gonzales, TX. In some embodiments, the nano-clay comprises montmorilionite, hectorite, or mixtures thereof. In some embodiments, the nano-clay comprises montmorilionite. In some embodiments, the nano-c!ay comprises hectorite.

Optionally, nano-clays may be surface modified to allow complete dispersion into and provide miscibility with the thermoplastic systems for which they were designed to be used, and are referred to herein as "modified nano-clay." For example, tetrasodium pyrophosphate ( a₄P2O₇) can be used to alter the surface activity of Laponite® particles. In some embodiments, the particulate filler comprises modified nano-clay.

Several forms of suitable nano-clay are available commercially from

Southern Clay Products division of Rockwood Additives, Gonzales, TX, under the trade name Laponite®. As represented by the manufacturer,

Laponite® refers generally to a synthetic 2:1 layered hydrous magnesium lithium silicate related to the smectite-group mineral hectorite and has the approximate empirical chemical formula: Na [(SieMgs.s Lio ₃)O2o(OH)₄].

For example, Laponite® OG is represented by the manufacturer as a synthetic sodium magnesium silicate composed of platelets about 83 nm long and 1 nm thick having a cation exchange capacity (CEC) of about 50

- 60 meq/100 g; Laponite® RD is represented by the manufacturer as a synthetic sodium magnesium silicate composed of platelets about 25 nm long and 1 nm thick and having a CEC of about 55 meq/100 g; Laponite®

B is represented by the manufacturer as a synthetic sodium magnesium fluorosiiicate composed of platelets about 55 nm long and 1 nm thick and having a CEC of about 100 meq/100 g; and Laponite® JS is represented by the manufacturer as a synthetic sodium magnesium fluorosiiicate composed of platelets about 40 nm long and 1 nm thick that has been treated with tetrasodium pyrophosphate and has a CEC of about 90 - 100 meq/100 g.

In some embodiments, the particulate filler comprises micropuip. As used herein, the term "micropuip" refers to an intermeshed organic material having two or more webbed, dendritic, branched, mushroomed, or fibril structures and a volume average length ranging from 0.01 to 100 micrometers, for example from 0.1 to 50 micrometers. Micropuip is made by contacting an organic fiber, for example short fiber, pulp, fibrids, or mixtures of these forms, with a medium comprised of a liquid component and a solid component, and then agitating the mixture to size reduce and modify the organic fiber to form micropuip dispersed in the liquid

component. Micropuip suitable for use as particulate filler in the resin binder layer of the ballistic composite articles disclosed herein can be made from fibers of aromatic polyamides including aramid,

poiybenzoxadiazoie, polybenzimidazole, or mixtures thereof.

Useful micropuips can also be made by refining short fibers between rotating discs to cut and shear the fibers into smaller pieces. Pulp particles differ from short fibers by having a multitude of fibrils or tentacles extending from the body of each pulp particle. These fibrils or tentacles provide minute hair-like anchors for reinforcing composite materials and cause the pulp to have a very high surface area. Aramid micropuip is well known in the art and can be made by refining aramid fibers comprising the aromatic poiyamide polymers poiy{p-phenylene terephthaiamide) and/or poiy(m-phenyiene isophthalamide) to fibriilate the short pieces of aramid fiber material. Such aramid micropuips have been reported to have a surface area in the range of 4.2 to 15 meters²/gram and a Kajaani weight average length in the range of 0.8 to 1 .1 millimeters (mm). Microscopy shows that these are generally on the order of 100 nm in diameter or less.

As used herein, the term "aramid" means a poiyamide wherein at least 85% of the amide (-CONH-) linkages are attached directly to two aromatic rings. Up to about 10 wt% of other polymeric material can be blended with the aramid, as well as copolymers having up to about 10 wt% of other diamine substituted for the diamine of the aramid, or up to about 10 wt% of other diacid chloride substituted for the diacid chloride of the aramid. Such organic fibers are disclosed in U.S. Patent Nos. 3,869,430; 3,889,429; 3,787,758; and 2,999,788. Aromatic polyamide organic fibers or materials derived from such fibers are known under the trademark KEVLAR^® fibers, KEVLAR^® aramid pulp, style 1 F543; 1 .5 mm KEVLAR^® aramid floe style 6F581 ; and Kevlar© Merge 1 F381 , and are available from E. I. du Pont de Nemours and Company, Wilmington, Delaware.

In some embodiments, the micropuip comprises aramid micropu!p. In some embodiments, the micropuip comprises polybenzoxadiazoie micropuip. In some embodiments, the micropuip comprises

poiybenzimidazoles micropuip. In some embodiments the micropuip has an average length in the range of from about 100 nm to about 100,000 nm.

The resin binder layer contains from about 4 wt% to about 50 wt% particulate filler, based on the total weight of particulate filler and thermoplastic material. In some embodiments, the resin binder layer contains an amount of particulate filler between and optionally including any two of the following values: 4 wt%, 5 wt%, 8 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 1 1 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, 18 wt%, 17 wt%, 18 wt%, 19 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt%, and 50 wt% based on the total weight of particulate filler and thermoplastic material.

Bailistic composite articles comprising a consolidated fabric section comprising two or more fibrous fabric layers and a resin binder layer as disclosed herein can provide both ballistic penetration protection and also blunt trauma protection upon projectile impact, i.e. reduced backface deformation. In some embodiments, the thermoplastic material of the resin binder layer comprises a poiyurethane, the initial tensile modulus of the resin binder layer as a resin binder film is in the range of about 100

MPa to about 300 MPa, and the resin binder layer contains from about 20 weight percent to about 50 weight percent particulate filler, based on the total weight of particulate filler and polyurethane. In some embodiments, the particulate filler comprises micropulp and the resin binder layer contains from about 30 weight percent to about 50 weight percent micropulp_., based on the total weight of micropulp and polyurethane. In some embodiments, the micropulp comprises aramid micropulp and the resin binder layer contains from about 30 weight percent to about 50 weight percent aramid micropulp, based on the total weight of aramid micropulp and polyurethane.

!n some embodiments, the thermoplastic material of the resin binder layer comprises a semi-crystalline acid ethylene copolymer, the initial tensile modulus of the resin binder layer as a resin binder film is in the range of about 100 MPa to about 1000 MPa, and the resin binder layer contains from about 8 weight percent to about 50 weight percent particulate filler, based on the total weight of particulate filler and semi- crystalline acid ethylene copolymer. In some embodiments, the particulate filler comprises micropulp and the resin binder layer contains from about 20 weight percent to about 40 weight percent micropulp, based on the total weight of micropulp and semi-crystalline acid ethylene copolymer, !n some embodiments, the micropulp comprises aramid micropulp.

In some embodiments, the thermoplastic material of the resin binder layer comprises a semi-crystalline acid ethylene copolymer and the particulate filler comprises nano-clay, the initial tensile modulus of the resin binder layer as a resin binder film is in the range of about 100 MPa to about 1000 MPa, and the resin binder layer contains from about 8 weight percent to about 25 weight percent nano-clay, based on the total weight of nano-clay and semi-crystalline acid ethylene copolymer. In some embodiments, the nano-clay comprises montmorilionite or hectorite.

In some embodiments, the thermoplastic material of the resin binder layer comprises a semi-crystalline acid ethylene copolymer and the particulate filler comprises nano-siiica. In some embodiments, the resin binder layer contains from about 20 weight percent to about 50 weight percent nano-silica, based on the total weight of nano-silica and semi- crystalline acid ethylene copolymer. In some embodiments, the nano- si!ica comprises colloidal silica.

The two or more fibrous fabric layers having a resin binder layer comprising a thermoplastic material and a particulate filler comprising nano-siiica, nano-ciay, micropulp, or mixtures thereof disposed between at least some of the fabric layers as disclosed herein can be made by applying a solution or dispersion containing the thermoplastic materia! and particulate filler to the fibrous fabric layers. Standard liquid coating methods can be used, for example rod coating, slot die, spray, roll, transfer, gravure, and dip coating, to apply the solution or suspension to the fabric layers. After drying, the resin binder layer is essentially continuous and covers the entire surface, or both surfaces, of the fabric layers. Typically, the particulate filler is uniformly dispersed in the thermoplastic material.

Multilayers of the coated fibrous fabric layers can then be pressed at high temperatures and pressures to consolidate them into rigid, solid single composite panels. Multilayers of the coated fibrous fabric layers can also be combined with additional ballistic layers comprising different fibrous materials, for example unidirectional polyethylene or

polypropylene, and consolidated to form rigid multicomposite panels. In some embodiments, a consolidated fabric section comprises a multitude of fibrous fabric layers, for example 10, 15, 20, 25, 30, 35, or more fibrous fabric layers. In some embodiments, a consolidated fabric section comprises ten or more fibrous fabric layers. In some embodiments, the ballistic composite article can further comprise a section of consolidated unidirectional fibrous layers comprising ultrahigh molecular weight polyethylene fiber or ultrahigh molecular weight polypropylene fiber.

In one embodiment, a rigid composite article comprises a

consolidated fabric section comprising two or more fibrous fabric layers and a resin binder layer disposed between at least some of the fabric layers, the resin binder layer comprising a thermoplastic material and a particulate filler comprising nano-siiica, nano-ciay, micropulp, or mixtures thereof; wherein

c) the resin binder layer is present in the consolidated fabric

section in an amount from about 8 weight percent to about 15 weight percent, based on the total weight of the resin binder layer and the fibrous fabric layers;

and wherein the consolidated fabric section is made by a process comprising the steps:

i) providing a fibrous fabric layer having a surface;

ii) providing a dispersion of thermoplastic material and a particulate filler comprising nano-silica, nano-clay, micropuip, or mixtures thereof, wherein the particulate filler has an average particle size of less than 500 nm in at least one direction;

iii) applying the dispersion to the surface of the fibrous fabric layer to obtain a coated fabric layer; and

iv) consolidating a multitude of the coated fabric layers under conditions of sufficient temperature and pressure to provide a consolidated fabric section. Conditions of sufficient temperature and pressure include a temperature in the range of 130 °C to 160 °C and a pressure in the range of about 6.9 MPa to about 27.6 MPa, for example.

Applying the resin binder layer as a dispersion of thermoplastic material and particulate filler to a fabric layer, as disclosed herein, enables preparation of consolidated fabric sections which could not be made by other means. For example, resin binder layers containing high levels of particulate filler, such as in Examples 4, 5, and 7 herein below, are typically not melt processable. Thus, a consolidated fabric section could not be formed by combining fabric layers and melt extruded or melt processed films of Examples 4, 5, and 7, because such polymeric films cannot be formed with high levels of particulate filler. Ballistic composite articles disclosed herein can provide higher penetration resistance as evidenced by higher V50, yet at the same time have higher structural stiffness. The composite articles disclosed herein are rigid and can be used to provide protection to the body or to property. Panels comprising such composite articles can be used in rigid armor applications such as helmets, tactical plates, structural members of helicopters, vehicles, walls, shelters, and other military equipment.

EXAMPLES

The methods described herein are illustrated in the following examples. From the above discussion and these examples, one skilled in the art can ascertain the essential characteristics of this invention, and without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various uses and conditions.

The following abbreviations are used: "°C" is degrees Celsius, "°F" is degrees Fahrenheit, "grn" is grain, "m" is meter, "s" is second, "psf is pounds per square foot, lb/ft²" is also pounds per square foot, "ft/s" is feet per second, "cm" is centimeter, "mm" is millimeter, "rim" is nanometer, "g" is gram, "kg" is kilogram, "g/m²" is grams per square meter, "gpd" is grams per denier, "mo!" is mole, "wt" is weight, "wt%" means weight percent, "Comp. Ex." is Comparative Example, "ASTM" is American Society for Testing and Materials.

Materials:

Ail commercial materials were used as received unless otherwise indicated.

Plies of Kevlar® S751 fabric under the trade name of Kevlar® para- aramid brand, were obtained from DuPont. The yarns of the fabric had a nominal yarn tenacity of 28 gpd and a nominal yarn modulus of 830 gpd. The nominal areal weight of the fabric was 170 g/m².

HB26 unidirectional cross-plied fibrous layers, available as consolidated sheets with an unfilled elastomer matrix binder, were obtained from DS Dyneema. The sheets contained high tenacity ultra high molecular weight polyethylene (UHMWPE) fiber. Michem® 4983 (Micheiman Co., Ohio) is an aqueous dispersion of eihylene-acry!ic acid copolymer containing 20 moI% acrylic acid

comonomer and no metal counterions, and having the following

characteristics: it is a low melting, low crystaliinity resin (T_m=72 °C) that has high melt flow at 190 °C once it is in a dried state. Thus, it has low melt viscosity. This polymer resin is referred to as Έ-ΑΑ-1 " herein.

Michem® 2960 (Micheiman Co., Ohio) is an aqueous dispersion of ethyiene-acryiic acid (E-AA) copolymer ionomer containing 10 moi% acrylic acid (AA) comonomer with a fairly high melting point (Tm-91 °C) because of the low percent acid comonomer. The counterion is potassium at 100% neutralization, and this polymer when dry is not melt extrudable because of its high degree of neutralization. This polymer resin is referred to as Έ-ΑΑ-2" herein.

An ethylene-methacryiic acid copolymer ionomer containing about 20 wt% methacrylic acid (MA) comonomer and 59% sodium ion (Na⁺) neutralization of the MA groups, made using standard polymerization procedures as disclosed in US 3,264,272 and US 3,355,319, was used as an aqueous solution and is referred to as Έ-ΜΑ-3" herein.

Sancure® 2710, an aqueous dispersion poiyurethane (PU) that is dried to an amorphous low glass transition elastomer and that has lower modulus than Sancure 899, was obtained from Lubrizoi Co. (Ohio). This polymer resin is referred to as "PU-1 " herein. Sancure® 899, an aqueous dispersion poiyurethane that is dried to an amorphous medium glass transition elastomer, was obtained from Lubrizoi Co. This polymer resin is referred to as "PU~2" herein.

Laponite® OG, a nano-clay available from Southern Clay Company, has a primary particle size of about 1 nm x 100 nm x 100 nm. Cioisite® CA++, also available from Southern Clay company, has a primary particle size of about 1 nm x 100 nm x 100 nm. Both of these clays can be dispersed in water. Ludox® TM-50, an aqueous colloidal silica suspension containing 30 nm silica particles, was obtained from DuPont (now available from W.R. Grace, Co.). Kevlar® Merge 1 F361 aramid pulp, obtained from DuPont and having a weight average length in the range of 0.8 mm to 0,8 mm, was media milled in water for 4 hours to produce the aramid micropulp used in the Examples. The aramid micropulp had an average length of 40 micrometers as measured by light scattering methods.

Genera! Procedures:

For each Example, an aqueous solution or dispersion of the thermoplastic material was combined with the aqueous particulate dispersion. Generally, vigorous mixing with a high shear mixer was applied for Laponite® OG and micro-pulps. Cioisite® type nano-ciays were directly sonicated in the dispersion using a Vibra-Ceii™ model VC750 probe sonicator (Sonics & Materials, Inc., Newtown, CT) at a frequency of 20 kHz, 30% amplitude, and 750 W. Sonication extended for at least 3 hours with cycles of 30 seconds of sonication followed by 30 seconds of rest until no settling of the Cioisite® dispersion was observed. These aqueous dispersion mixtures of thermoplastic material and particulate filler were then used to coat the fibrous fabric sheets as follows. Comparative Examples used an aqueous solution or dispersion of the thermoplastic material without fillers.

Twelve inch (30.5 cm) wide strips of Kevlar® S751 fabric plies about 6 ft. (200 cm) long were rod coated on one surface with an aqueous mixture containing thermoplastic material only (for the Comparative

Examples) or a dispersion mixture of thermoplastic material and

particulate filler (for the Examples), then dried overnight on the benchtop at 20 °C or in a drying oven for a few minutes at temperatures of 100 °C to

150 °C. The thickness of the coating layer deposited on the Kevlar® ply was adjusted by choosing different rod sizes and levels of dilution of the coating solution to give the desired solid coating weight fraction as a function of the weight of the Kevlar-® fabric. In some cases multiple coating passes were made. The dispersion was generally applied to coat the entire fabric surface in order to provide good bonding over the entire fabric surface during consolidation. After the coated plies were dried, the resin binder layer content of the plies was generally 8-15 wt% based on the total weight of the fabric, the polymeric resin, and particulate filler. The coated plies were cut to the desired size.

In the Examples and the Comparative Examples, the coated Kevlar® fabric layers were combined with unidirectional fibrous layers twelve inch (30.5 cm) long by twelve inch (30.5 cm) wide and consolidated using the following procedure to produce solid multilayer ballistic panels having all layers bonded together. The coated Kevlar® fabric plies were laid up such that the one-sided resin binder layer was always facing the same direction, thus the coated side of one ply was always in direct contact with the dry or un-coated side of an adjacent ply, and vice versa. The coated Kevlar® fabric layers were combined with an equal weight of HB28 unidirectional fibrous layers of the same length and width, where all layers of HB26 were positioned on the strikeface of the layup, and the Kevlar® layers all combined together separate from the HB28 layers on the backface. The layup was placed in a compression molding press to undergo a consolidation procedure in which the plies were consolidated into a single solid multilayer ballistic panel. In some cases the coated Kevlar® plies and HB28 unidirectional fiber layers were consolidated separately, and then combined in a third consolidation step to make a single solid composite panel with all layers bonded together.

Consolidation took place at a temperature of 130 °C (288 °F), under a pressure of 27.6 MPa (4000 psi), for a time of about 25 minutes, prior to cooling down to a temperature below 38 °C (100 °F). The 27.8 MPa (4000 psi) pressure was maintained on the layup during the entire process including the cooling phase. The panel was then removed from the moid and evaluated for ballistic performance.

The panels of the Examples were thus consolidated, rigid, multilayer composite articles which contained as the consolidated fabric section thirty layers of Kevlar® fabric having a resin binder layer between the Kevlar® fabric layers, the resin binder layers containing the

thermoplastic material and particulate filler as indicated below in each Example. In addition to the consolidated fabric section, the panels also contained a section of consolidated unidirectional fibrous fabric layers of ultrahigh molecular weight polyethylene fiber.

Area! density of the consolidated Kevlar©-containing fabric sections, the consolidated unidirectional polyethylene fibrous fabric layers, and the consolidated rigid ballistic composite panels which contained both the consolidated KeviarO-containing fabric section and the consolidated unidirectional polyethylene fibrous fabric layers is reported as weight per unit area and was determined by weighing 12 inch x 12 inch panels (30.5 cm x 30.5 cm) of material.

Analytical Methods:

Tensile tests: Films of thermoplastic resin binder layers containing particulate fillers (Examples), and films of thermoplastic resin binder layers without particulate fillers (Comparative Examples), were thermaiiy pressed at 180 °C and 200 psi from dried polymer dispersions or polymer emulsions which contained less than 1 wt% moisture before pressing.

Drying was about 1 hour at 1 10 °C before the thermal pressing. For each

Example, the resin binder layer composition used to prepare the resin binder film was the same composition used to coat the Keviar® fabric plies. For each Comparative Example, the composition used to prepare the unfilled resin film was the same composition used to coat the fabric plies. For the tensile tests there was no ballistic fiber material in the resin binder films. The thicknesses and widths of the tensile films were measured to give exact cross-sectional areas that were used for determining the force per unit cross-sectional area (psi or MPa where

0.0089 psi=1 MPa). The films were about 0.02 inch (0.051 cm) thick by 0.2 inch (0.51 cm) wide and 2 inches (5.1 cm) long. The films were evaluated with the method described in ASTM D882. The films were gripped in an instron and tensile stress-strain curves were obtained at 50%/min elongation rates, where the stress is the above mentioned force per unit cross-sectional area. This is a common method to measure stress-strain curves for ductile and elastomeric materials. The tensile modulus was determined from the initial slope of the stress-strain curves, and is sometime referred to as Young's modulus. Ballistic Penetration Performance: Baiiistic tests of the panels of the Examples and Comparative Examples were conducted in accordance with standard procedure !V1!L-STD-662-F (V50 Ba!iistic Test for Armor) with the exception that 17 Grain Right Circular Cylinder (RCC) fragment- simulating projectiles were used. For each Example and Comparative Example, one composite panel was used as the target with up to seven shots fired at it, at zero degree obliquity. The composite panels were oriented with the consolidated HB26 unidirectional fiber layers facing the projectile, that is, with the HB28 unidirectional fiber layers on the strikeface of the composite panel. The reported V50 values are average values for the number of pairs of partial and complete penetrations achieved for each example. V50 is a statistical measure that identifies the average velocity at which a buiiet or a fragment penetrates the target or armor equipment in 50% of the shots, versus non-penetration of the other 50%. The parameter measured is V50 at zero degrees where the degree angle refers to the obliquity of the projectile to the target.

Comparative Example A

Following the general procedures described above, 30 plies of Kevlar® S751 fabric were coated using an aqueous suspension containing E-AA-1 and no particulate filler, then thermally consolidated together with an equal weight of HB26 layers to give a rigid panel having total area! density of 2.2 lb/ft². The consolidated KevSar®-fabric containing section of the panel contained 1 1 wt% E-AA-1 (unfilled resin binder layer to the total weight of fabric and resin) and had an area! density of 1 .1 lb/ft².

Comparative Example B

Thirty plies of Kevlar® S751 fabric were coated using an aqueous suspension containing E-AA-1 and aramid micropulp, then thermally consolidated together with an equal weight of HB28 layers to give a rigid panel having total areal density of 2.2 lb/ft'^". The consolidated Kevlar®- fabric containing section of the panel had an areal density of 1 .1 lb/ft² and contained 1 1 wt% resin binder layer, based on the total weight of resin binder to the total weight of fabric and resin binder. The resin binder layer contained 7 wt% aramid micropu!p, based on the total weight of the aramid rnicropulp and the E-AA-1 .

Example 1

The procedure of Comparative Example B was followed, except an aqueous suspension containing a different ratio of aramid rnicropulp to E- AA-1 was used to provide a resin binder layer which contained 37 wt% aramid rnicropulp based on the total weight of the aramid rnicropulp and the E-AA-1 . The consolidated Keviar®-fabric containing section of the panel had an area! density of 1 .1 lb/ft² and contained 1 1 wt% resin binder layer, based on the total weight of resin binder to the total weight of fabric and resin binder.

Example 2

30 plies of Kevlar© S751 fabric were coated using an aqueous suspension containing E-AA-1 and Ludox® silica nano-particies, then thermally consolidated together with an equal weight of HB28 layers to give a rigid panel having total areal density of 2.2 lb/ft². The consolidated Kevlar®-fabric containing section of the panel had an area! density of 1 .1 lb/ft² and contained 1 1 wt% resin binder layer, based on the total weight of resin binder to the total weight of fabric and resin binder. The resin binder layer contained 40 wt% silica particulate filler based on the total weight of the silica and the E-AA-1 .

Comparative Example C

Following the general procedures described above, 30 plies of Kevlar® S751 fabric were coated using an aqueous suspension containing E-AA-2 and no particulate filler, then thermally consolidated together with an equal weight of HB28 layers to give a rigid panel having total areal density of 2.2 lb/ft². The consolidated Kev!ar®-fabric containing section of the panel contained 1 1 wt% E-AA-2 (unfilled resin binder to the total weight of fabric and resin) as the unfilled resin binder layer and had an area! density of 1 .1 lb/ft².

Example 3

30 plies of Kev!ar® S751 fabric were coated using an aqueous suspension containing E-AA-2 and aramid micropuip, then thermally consolidated together with an equal weight of HB26 layers to give a rigid panel having total area! density of 2.2 lb/ft². The consolidated Kevlar®- fabric containing section of the panel had an areal density of 1 .1 Ib/ff and contained 1 1 wt% micropuip filled E-AA-2 resin binder layer, based on the total weight of resin binder to the total weight of fabric and resin binder. The resin binder layer contained 17 wt% micropuip particulate filler based on the total weight of the filler and the E-AA-2.

Example 4

The procedure of Example 3 was followed except an aqueous suspension containing a different ratio of particulate aramid micropuip to E-AA-2 to was used to provide a resin binder layer which contained 37 wt% aramid micropuip based on the total weight of the aramid micropuip and the E-AA-2. The consolidated Kevlar®-fabric containing section of the panel had an areal density of 1 .1 lb/ft² and contained 1 1 wt% resin binder layer, based on the total weight of resin binder to the total weight of fabric and resin binder.

Example 5

30 plies of Kevlar® S751 fabric were coated using an aqueous suspension containing E-AA-2 and Ludox® silica nano-particies, then thermally consolidated together with an equal weight of HB26 layers to give a rigid panel having total areal density of 2.2 lb/ft². The consolidated Kevlar®-fabric containing section of the panel had an area! density of 1 .1 lb/ft² and contained 1 1 wt% silica filled E-AA-2 resin binder layer, based on the total weight of resin binder to the total weight of fabric and resin binder. The resin binder layer contained 40 wt% silica particulate filler based on the total weight of the silica and the E-AA-2.

Example 6

31 plies of Keviar® S751 fabric were coated using an aqueous suspension containing E-AA-2 and Cloisite® nano-clay, then thermally consolidated together with an equal weight of HB26 layers to give a rigid panel having total areal density of 2.2 lb/ft². The consolidated Kevlar®- fabric containing section of the panel had an areal density of 1 .1 Ib/ff and contained 1 1 wt% particulate nano-clay filled resin binder layer, based on the total weight of resin binder to the total weight of fabric and resin binder. The resin binder layer contained 10 wt% Cloisite® particulate filler based on the total weight of the filler and the E-AA-2.

Example 7

The procedure of Example 8 was followed except an aqueous suspension containing a different ratio of Cloisite® particles to E-AA-2 was used to provide a resin binder layer which contained 20 wt% Cloisite® particulate filler based on the total weight of the filler and the E-AA-2.

The consolidated Kevlar®-fabric containing section of the panel had an areal density of 1 .1 lb/ft² and contained 1 1 wt% resin binder layer, based on the total weight of resin binder to the total weight of fabric and resin binder.

Comparative Example D

Following the general procedures described above, 30 plies of Keviar® S751 fabric were coated using an aqueous suspension containing E-MA-3 and no particulate filler, then thermally consolidated together with an equal weight of HB28 layers to give a rigid panel having total area! density of 2.2 lb/ft². The consolidated Kev!ar®-fabric containing section of the panel contained 1 1 wt% E-MA-3 (unfilled resin binder to the total weight of fabric and unfilled resin binder) and had an area! density of 1 .1 lb/ft². Example 8

31 plies of Kevlar® S751 fabric were coated using an aqueous suspension containing E-MA-3 and Laponite OG© nano-clay, then thermally consolidated together with an equal weight of HB28 layers to give a rigid panel having total areal density of 2.2 lb/ft². The consolidated Kevlar©-fabric containing section of the panel had an area! density of 1 .1 lb/ft² and contained 1 1 wt% E-MA-3 nano-clay filled resin binder layer, based on the total weight of resin binder to the total weight of fabric and resin binder. The resin binder layer contained 9 wt% Laponite OG© particulate filler based on the total weight of the filler and the E-MA-3.

Example 9

The procedure of Example 8 was followed except an aqueous suspension containing a different ratio of Laponite OG® particles to E-MA- 3 was used to provide a resin binder layer which contained 18 wt%

Laponite OG© particulate filler based on the total weight of the filler and the E-MA-3. The consolidated Keviar®-fabric containing section of the panel had an area! density of 1 .1 lb/ft² and contained 1 1 wt% resin binder layer, based on the total weight of resin binder to the total weight of fabric and resin binder.

Comparative Example E

Following the general procedures described above, 30 piles of Kevlar© S751 fabric were coated using an aqueous suspension containing PU-1 and no particulate filler, then thermally consolidated together with an equal weight of HB28 layers to give a rigid panel having total areal density of 2.2 lb/ft². The consolidated Kevlar@-fabric containing section of the panel contained 1 1 wt% PU-1 (unfilled resin binder to the total weight of fabric and resin) as the unfilled resin binder layer and had an areal density of 1 .1 lb/ft².

Comparative Example F 30 plies of Kevlar® S751 fabric were coated using an aqueous suspension containing PU-1 and aramid micropulp, then thermally consolidated together with an equal weight of HB28 layers to give a rigid panel having total areal density of 2.2 !b/ftA The consolidated Kevlar®- fabric containing section of the panel had an areal density of 1 .1 lb/ft² and contained 1 1 wt% micropulp filled PU-1 resin binder layer, based on the total weight of resin binder to the total weight of fabric and resin binder. The resin binder layer contained 1 1 wt% micropulp particulate filler based on the total weight of the filler and PU-1 .

Comparative Example G

The procedure of Comparative Example F was followed except an aqueous suspension containing a different ratio of aramid micropulp to PU-1 was used to provide a resin binder layer which contained 17 wt% aramid micropulp particulate filler based on the total weight of the filler and the PU-1 . The consolidated Keviar®-fabric containing section of the panel had an area! density of 1 .1 lb/ft² and contained 1 1 wt% resin binder layer, based on the total weight of resin binder to the total weight of fabric and resin binder.

Example 10

The procedure of Comparative Example F was followed except an aqueous suspension containing a different ratio of aramid micropulp to PU-1 was used to provide a resin binder layer which contained 37 wt% aramid micropulp particulate filler based on the total weight of the filler and the PU-1 . The consolidated Kevlar®-fabric containing section of the panel had an area! density of 1 .1 lb/ft² and contained 1 1 wt% resin binder layer, based on the total weight of resin binder to the total weight of fabric and resin binder.

Example 1 1

30 plies of Kevlar® S751 fabric were coated using an aqueous suspension containing PU-2 and aramid micropulp, then thermally consolidated together with an equai weight of HB26 layers to give a rigid panel having total areal density of 2.2 lb/ft². The consolidated Keviar®- fabric containing section of the panel had an areal density of 1 .1 lb/ft² and contained 1 1 wt% micropuip PU-2 resin binder layer, based on the total weight of resin binder to the total weight of fabric and resin binder. The resin binder layer contained 30 wt% aramid micropuip particulate filler based on the total weight of the filler and the PU-2.

Data from the characterization of the resin binder layers as resin binder films, and the ballistic performance of the panels, of the Examples and Comparative Examples are presented in Table 1 .

Table. 1 . Characterization of the Resin Binder La ers and Ballistic Performance of the Composite Panels

* Determined as a resin binder film (Examples) or as an unfilled resin binder film (Comparative Examples).

nd" means not determined

Data from Table 1 are plotted in the Figures to illustrate the relationships between resin binder properties and composite panel V50. Addition of particulate fillers such as aramid micro-pulp, nano-siiica, and nano-clays such as hectorite (Laponite©) and montmorillonite (Cloisite®) into the thermoplastic materials of the resin binder layers can provide higher initial tensile modulus in tensile film studies (Table 1 ). Use of resin binder layers containing these particulate fillers also improves the V50 value of the composite panel containing the resin binder layers, as shown in Figs. 1 and 2. This is because the presence of the particulate filler causes the lower strain to failure which is a measure of lower toughness of the resin binder films (see elongation at break values in Table 1 which give the % elongation at failure), which leads to higher energy dissipation upon impact as the resin layers can fracture more easily. Furthermore, the composite panel retains high panel stiffness due to the high initial tensile modulus of the filled resin binders. High panel stiffness is important for blunt trauma protection upon impact, i.e. to reduce backface deformation. This is especially important for poiyurethanes that have very low stiffness as is seen in their low initial tensile modulus (Table 1 ).

Added filler improves V50 and increases binder resin modulus

substantially for such poiyurethanes.

Claims

CLAHMS What is claimed is:

1 . A rigid ballistic composite article, the article comprising:

wherein

c) the resin binder layer is present in the consolidated fabric

2. The composite article of claim 1 , wherein the micropulp comprises aramid micropulp.

3. The composite article of claim 1 , wherein the nano-clay comprises montmoril!onite, hectorite, or mixtures thereof.

4. The composite article of claim 1 , wherein the initial tensile modulus is in the range of about 100 MPa to about 850 MPa.

5. The composite article of claim 1 , wherein the resin binder layer contains from about 4 weight percent to about 50 weight percent particulate filler, based on the total weight of particulate filler and thermoplastic material.

8. The composite article of claim 1 , wherein the thermoplastic material comprises a semi-crystalline acid ethylene copolymer, a polyurethane, a linear low density polyethylene, or combinations thereof.

7. The composite article of claim 8, wherein the thermoplastic material comprises a semi-crystalline acid ethylene copolymer and the particulate filler comprises nano-siiica.

8. The composite article of claim 8, wherein the thermoplastic material comprises a polyurethane, the initial tensile modulus is in the range of about 100 MPa to about 300 Pa, and the resin binder layer contains from about 20 weight percent to about 50 weight percent particulate filler, based on the total weight of particulate filler and polyurethane.

9. The composite article of claim 8, wherein the particulate filler comprises aramid micropulp and the resin binder layer contains from about 30 weight percent to about 50 weight percent aramid micropulp, based on the total weight of aramid micropulp and polyurethane.

10. The composite article of claim 8, wherein the thermoplastic material comprises a semi-crystalline acid ethylene copolymer, the initial tensile modulus is in the range of about 100 MPa to about 1000 MPa, and the resin binder layer contains from about 8 weight percent to about 50 weight percent particulate filler, based on the total weight of particulate filler and semi-crystalline acid ethylene copolymer.

1 1 . The composite article of claim 10, wherein the particulate filler comprises micropulp and the resin binder layer contains from about 20 weight percent to about 40 weight percent micropulp, based on the total weight of micropulp and semi-crystalline acid ethylene copolymer.

12. The composite article of claim 10, wherein the particulate filler comprises nano-clay, and the resin binder layer contains from about 8 wt% to about 25 wt% nano-clay, based on the total weight of nano-clay and the semi-crystalline acid ethylene copolymer.

13. The composite article of claim 1 , wherein at least one fibrous fabric layer comprises a woven fabric comprising poiy(p-phenyiene

terephthaiamide) fiber.

14. The composite article of claim 1 , wherein at least one fibrous fabric layer comprises a unidirectional fabric.

15. The composite article of claim 1 , wherein a first fibrous fabric layer comprises a first polymer, and a second fibrous fabric layer comprises a second polymer, and the first and second polymers are different.

16. The composite article of claim 1 , wherein at least one fibrous fabric layer comprises a polymer comprising aramid, ultra-high molecular weight high density polyethylene, ultra-high molecular weight high density polypropylene, polyvinyl alcohol, polyazole, or combinations or blends thereof.

17. The composite article of claim 1 , wherein the consolidated fabric section comprises ten or more fibrous fabric layers.

18. The composite article of claim 1 , further comprising a section of consolidated unidirectional fibrous layers comprising ultrahigh molecular weight polyethylene fiber or ultrahigh molecular weight polypropylene fiber.

19. The composite article of claim 1 , wherein the particulate filler has an average particle size of less than 30 nm in at least one dimension.

20. A thermally pressed stiff panel comprising the composite article of claim 1 .

21 . A helmet comprising the composite article of claim 1 .

22. The composite article of claim 1 , wherein the consolidated fabric section is made by a process comprising the steps:

i) providing a fibrous fabric layer having a surface;

iv) consolidating a multitude of the coated fabric layers under conditions of sufficient temperature and pressure to provide a consolidated fabric section.