CA1244300A - Ballistic-resistant fabric article - Google Patents

Abstract

BALLISTIC-RESISTANT FABRIC ARTICLE
ABSTRACT
The present invention provides an improved fabric which comprises at least one network of fibers selected from the group consisting of extended chain polyethylene (ECPE) extended chain polypropylene (ECPP) fibers, extended chain polyvinyl alcohol fibers and extended chain polyacrylonitrile fibers. A low modulus elasto-meric material, which has a tensile modulus of less than about 6,000 psi, measured at about 23°C, substantially coats the fibers of the network. Preferably, the fibers have a tensile modulus of at least about 500 grams/denier and an energy-to-break of at least about 22 Joules/gram.

Description

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BALLISTIC-RESISTANT FABRIC _ TICLE
DESCRIPTION
BACKGROUND OF THE INVENTION
Ballistic resistant articles such as bulletproof 5 vests, curtains, mats, raincoats and umbrellas con-taining high strength fibers are known. Fibers con-ventionally used include aramid fibers such as poly(phenylenediamine terephthalamide~, nylon fibers, glass fibers and the like. For many applications, such 10 as vests or parts of vests, the fibers are used in a woven or knitted fabric.
In "The Application of High Modulus Fibers to Ballistic Protection" R. C. Laible et al., J.
Macromol. Sci.-Chem. A7(1), pp. 295-322 1973, it is 15 indicated on p. 298 that a fourth requirement is that the textile material have a high degree of heat resis-tance; for example, a polyamide material with a meltiny point of 255C appears to possess better impact proper-ties ballistically than does a polyolefin fiber with 20 equivalent tensile properties but a lower melting point.
J.W.S. Hearle, et al.; "Ballistic Impact Resistance of Multi-Layer Textile Fabrics,i' NTIS Acquisition No. AD
A127641, (1981); disclose that coatings did not improve the ballistic performance of Kevlar 29 fabric. C. E.
25 Morris, et al.; Contract No. A 93 B/189 (1980); disclose that the addition of a rubber matrix to a Kevlar fabric seriously reduced its ballistic performance. W. Stein;
"Construction and Action of Bullet Resistant Vests,"
Melli and Textilberichte, 6/1981; discloses that coat-30 ings produced no improvement in ballistic resistance.R. C. Laible; "Fibrous Armor", Ballistic Materials and Penetration Mechanics, Elsevier Scientific Publishing Co. (1980); discloses on page 81 that attempts to raise the ballistic resistance of polypropylene yarns to the 35 level predicted from the yarn stress-strain properties by the application of selected coatings were unsuccess-ful.

3(10 BRIEF DESCRIPTION OF THE INVENTION
The present invention provides an improved, flexi-ble fabric which is particularly useful as, ballistic-resistant "soft" armor. The fabric is comprised of at 5 least one a network layer of high strength, extended chain polyolefin (ECP) fibers selected from the group consisting of extended chain polyethylene (ECPE) and extended chain polypropylene (ECPP) fibers, extended chain polyvinyl alcohol (PVA) fiber, and extended chain 10 polyacrylonitrile (PAN) fiber. The fiber of the network is coated with a low modulus elastomeric material which has a tensile modulus of less than about 6,000 psi (41,300 kPa). Preferably, the fibers have a tensile modulus of at least about 500 grams/denier and an 15 energy-to-break of at least about 22 Joules/ gram.
Compared to conventional ballistic-resistant fabric structures, the fabric of the present invention can advantageously provide a selected level of ballistic protection while employing a reduced weight of protec-20 tive material. Alternatively, the fabric of the presentinvention can provide increased ballistic protection when the article has a weight equal to the weight of a conventionally constructed piece of flexible, fabric-type armor.
DETAILED DESCRIPTION OF THE INVENTION

For the purposes of the present invention, a fiber is an elongate body the length dimension of which is much greater than the transverse dimensions of width and thickness. Accordingly, the term fiber includes single 30 filament, ribbon, strip, and the like having regular or irregular cross-section.
A fabric of the present invention includes at least one network comprised of a high strength, extended chain polyolefin ~ECP) fibers selected from the group consist-ing of extended chain polyethylene and extended chainpolypropylene fibers, extended chain PVA fiber and extended chain PAN fiber. The fibers of the network are coated with a low modulus elastomeric material which has 12~ 0 a tensile modulus of less than about 6,000 psi (~1,300 kPa), measured at room temperature US Patent Nos. 4,413,110, 4,440,711, 4,535,027 and 4,457,985 generally discuss the hiyh strength, extended 5 chain fiber, employed in the present invention.

Suitabl0 polyethylene fibers are those having a molecular weight of at least 500,000, preferably at 10 least one million and more preferably between two mil-lion and five million. Such extended chain polyethylene (ECPE~ fibers may be grown in solution such as described in U.S. Patent No. 4,137,394 to Meihuzen et al., or U.S. Patent No. 4,356,138 of Kavesh et al., issued 15 October 26, 1982, or a fiber spun from a solution to form a gel structure, as described in ~erman Off.
3,004,699 and GB 2051667, and especially as described in U.S. Patent ~b. 4,551,296.
(see EPA 64,167, published Nov. 10, 20 1982) . Depending upon the formation technique, the draw ratio and temperatures, and other conditions, a variety of properties c~n be imparted to these fibers. The tenacity of the fiber~ should be at lea~t 15 grams/
denier, prefer~bly at least 20 grams/denier, more 25 preferably Dt least 25 grams/denier and most preferably at least 30 grams/denier. Similarly, the tensile modu-lus of the fibers, a~ measured by an Instron tensile testing machine, is at least 300 grams/denier, prefera-bly at least 500 grams/denier and more preferably at 30 least 1,000 grams/denier and most preferably at least 1,500 grams/denier. These highest values for tensile modulus and tenacity are generally obtainable only by employing solution grown or gel fiber processes. Many of the fibers have melting points higher than the melt-ing point of the polymer from which they were formed.Thus, for example, ultra-high molecular weight poly-ethylenes of 500,000, one million and two million gen-erally have melting points in the bulk of 138C. The ,,.1 1'2'~

highly oriented polyethylene fibers. made of these materials have melting points 7 - }3C higher. Thus, a slight increase in melting point reflects the crystalline perfection of the fibers. Nevertheless, the 5 melting points of these fihers remain substantially below nylon; and the efficacy of these fibers for ballistic resistant articles is contrary to the various teachings cited above which indicate temperature resistance as a critical factor in selecting ballistic 10 materials.
Similarly, highly oriented extended chain poly-propylene (ECPP) fibers of molecular weight at least 750,000, preferably at least one million and more preferably at least two million may be used. Such 15 ultra-high molecular weight polypropylene may be formed into reasonably well oriented fibers by the techniques prescribed in the various references referred to above, and especially be the technique of U.S. Patent Nb. 4,413,110.

Since polypropylene is a much less crystal-line material than polyethylene and contains pendant methyl groups, tenacity values achievable with poly-propylene are gen~rally substantially lower than the 25 corresponding values for polyethylene. Accordingly, a suitable tenacity is at least 8 grams/denier, with a preferred t~enacity being at least 11 grams/denier. The tensile modulus for the polypropylene is at least 160 grams/denier, preferably at least 200 grams/denier. The 3~ 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 168C, more preferably at least 170C. The particularly preferred ranges for the above-described parameters can advantageously provide improvedperformance in the final article.
For improved ballistic resistance of the fabric article, the ECP fiber preferably has a tensile modulus 12~ 3()0 which preferably is at least about 500 g/den, more preferably is at least about 1000 g/den and most preferable is at least about 1300 g/den. Additionally, the ECP fiber has an energy-to-break which preferably is 5 at least about 22 J/g, more preferably is at least about 50 J/g and most preferably is at least 55 J/g.
As used herein, the terms polyethylene and poly-propylene mean predominantly linear polyethylene and polypropylene materials that may contain minor amounts 10 of chain branching or comonomers not exceeding 5 modi-fying units per 100 main chain carbon atoms, and that may also contain admixed therewith not more than about 25 wt% of one or more polymeric additives such as alkene-l-polymers; in particular, low density polyethy-15 lene, polypropylene or polybutylene, copolymers con-taining mono-olefins as primary monomers, oxidized polyolefins, graft polyolefin copolymers and polyoxy-methylenes, or low molecular weight additives such as anti-oxidants, lubricants, ultra-violet screening 20 agents, colorants and the like which are commonly incorporated therewith.
In the case of polyvinyl alcohol (PV-OH), PV-OH
fiber of molecular weight of at least about 500,000, preferably at least about 750,000, more preferably 25 between about 1,000,000 and about 4,000,000, and most preferably between about 1,500,000 and about 2,500,000 may be employed in the present invention. Particularly useful PV-OH fiber should have a modulus of at least about 300 g/denier, a tenacity of at least about 7 30 g/denier (preferably at least about 10 g/denier, more preferably at about 14 g/denier, and most preferably at least about 17 g/denier), and an energy to break of at least about 22 joules/g. PV-OH fibers having a weight average molecular weight of at least about 500,000, a tenacity of at least about 300 g/denier, a modulus of at least about 10 g/denier, and an energy to break of about 22 joules/g are more useful in producing a ballistic resistant article. PV-OH fiber having such properties ~2 ~'~3()0 can be produced, for example, by the process disclosed in U.S. Patent ~. 4,440,711, filed January 11, 1984, to Kwon et al., and commonly assigned.
In the case of polyacrylonitrile (PAN), PAN fiber 5 of molecular weight of at least about 400,000, and preferably at least 1,000,000 may be employed.
Particularly useful PAN fiber should have a tenacity of at least about 10 g/denier and an energy to break of at least about 22 joulejg. PAN fiber having a molecular lO weight o at least about 400,000, a tenacity of at least about 15-20 g/denier and an energy to break of at least about 22 joule/g is most useful in producing ballistic resistant articles; and ~uch fibers are disclosed, for example, in U.S. 4,535,027.
lS In the fabrics of the invention, the fiber network can have various configurations. For example, a plurality of fibers can be grouped together to form a twisted or untwisted yarn. The fibers or yarn may be formed as a felt, knitted or woven (plain, basket, satin 20 and crow feet weaves, etc.) into a network, or formed into a network by any of a variety of conventional techniques. For example, the fibers may be formed into woven or nonwoven cloth by conventional techniques.
A preferred embodiment of the present invention 25 includes multiple layers of coated fiber networks. The layers individually retain the high flexibility char-acteristic of textile fabrics and remain ceparate from each other. The multilayer article exhibits the flexi-bility of plied fabrics.

Vests and other articles of clothing comprised of multiple layers of fabric con-structed in accordance with the present invention havegood flexibility and comfort coupled with excellent bal-listic protection.

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The flexibility of the ballistic resistant fabric structures of the present invention is demonstrated by the following test: A 30 cm square fabric sample COm-prised of multiple fabric layers having a total areal 5 density of 2 kg/m2 when clamped horizontally along one side edge, will drape so that the opposite side edge is at least 21 cm below the level of t:he clamped side.
The multiple ]ayers of fabric may be stitched together to provide a desired level of ballistic pro-10 tection, for example, as against multiple ballisticimpacts. However, stitching can reduce the flexibility of the fabric.
The fibers or yarns are coated with a low modulus, elastomeric material comprising an elastomer coating 15 with this material substantially increases the ballistic resistance of the network. The elastomeric material has a tensile modulus, measured at about 23C, of less than about 6,000 psi (41,300 kPa). Preferably, the tensile modulus of the elastomeric material is less than about 20 5,000 psi (34,500 kPa), more preferably, is less than 1,000 psi (6,900 kPa) and most preferably is less than about 500 psi (3,450 kPa) to provide even more improved performance. The glass transition temperature (Tg) of the elastomer of the elastomeric material (as evidenced 25 by a sudden drop in the ductility and elasticity of the material) is less than about 0C. Preferably, the Tg of the elastomer is less than about -40C, and more preferably is less than about -50C. The elastomer also has an elongation to break (measured at about 23C) of 30 at least about 50%. Preferably, the elongation to break is at least about 100%, and more preferably, it is about 300% for improved performance.

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Coated fibers may be arranged (in the same fashion as uncoated fibers) into woven, non-woven or knitted fabrics. The fabric layers may be arranged in parallel arrays and/or incorporated into multilayer fabric arti-5 cles. Furthermore, the fibers, used either alone orwith coatings, may be wound or connected in a conven-tional fashion.
The proportion of coating on the coated fiber may vary from relatively small amounts (e.g. 0.1~ by weight 10 of fibers) to relatively large amounts (e.g. 60% by weight of fibers), depending upon whether the coating material has any ballistic-resistant properties of its own (which is generally not the case) and upon the rigidity, shape, heat resistance, wear resistance, flam-15 mability resistance and other properties desired for thefabric. In general, ballistic resistant fabrics of the present invention containing coated fibers should have a relatively minor proportion of coating (e.g. 0.1-30%, by weight of fibers), since the ballistic-resistant 20 properties are almost entirely attributable to the fiber. Nevertheless, coated fabrics with higher coating contents may be employed.
The coating may be applied to the fiber in a variety of ways. One method is to apply the neat resin 25 of the coating material to the fibers either as a liquid, a sticky solid or particles in suspension or as a fluidized bed. Alternatively, the coating may be applied as a solution or emulsion in a suitable solvent which does not adversely affect the properties of the 30 fiber at the temperature of application. While any liquid capable of dissolving or dispersing the coating polymer may be used, preferred groups of solvents include water, paraffin oils, aromatic solvents or hydrocarbon solvents, with illustrative specific sol-35 vents including paraffin oil, xylene, toluene andoctane. The techniques used to dissolve or disperse the coating polymers in the solvents will be those conven-tionally used for the coating of similar elastomeric ~'f~ ;3()C3~

materials on a variety of substrates.
Other techniques for applying the coating to the fibers may be used, including coating of ~he high modu-lus precursor (gel fiber) before the high temperature 5 stretching operation, either before! or after removal of the solvent from the fiber, The fiber may then be stretched at elevated temperatures to produce the coated fibers. The gel fiber may be passed through a solution of the appropriate coating polymer (solvent may be 10 paraffin oil, aromatic or aliphatic solvent) under con-ditions to attain the desired coating. Crystallization of the high molecular weight polyethylene in the gel fiber may or may not have taken place before the fiber passes into the cooling solution. Alternatively, the 15 fiber may be extruded into a fluidized bed of the appro-priate polymeric powder.
If the fiber achieves its final properties only after a stretching operation or other manipulative pro-cess, e.g. solvent exchanging, drying or the like, it is 20 contemplated that the coating may be applied to the pre-cursor material. In this embodiment, the desired and preferred tenacity, modulus and other properties of the fiber should be judged by continuing the manipulative process on the fiber precursor in ~ manner corresponding 25 to that employed on the coated fiber precursor. Thus, for example, if the coating is applied to the xerogel fiber described in U.S. Patent No. 4,551,296 of Kavesh et al., and the coated xerogel fiber is then stretched under defined temperature and stretch ratio 30 conditions, the applicable fiber tenacity and fiber modulus values would be the mea ured values of an uncoated xerogel fiber which is similarly stretched.
A preferred coating technique is to form network layer and then dip the layer into a bath o a solution 35 containing the low modulus elastomeric coating material. Evaporation of the solvent produces an elastomeric material coated fiber network. The dipping procedure may be repeated several times as required to 12'~'~300 place a desired amount of elastomeric material coating on the network fibers.
A wide variety of elastomeric materials and formu-lations may be utilized in this invention. The essen-5 tial requirement is that the elastomeric material havethe appropriately low modulus. Representative examples o suitable elastomers of the elastomeric material have their structures, properties, formulations together with crosslinking procedures summarized in the Encyclopedia 10 of Polymer Science, Volume 5 in the section "Elastomers-Synthetic" (John Wiley & Sons Inc., 1964). For example, any of the following elastomers may be employed: polybutadiene, polyisoprene, natural rubber, ethylene-propylene copolymers, ethylene-propylene-diene 15 terpolymers, polysulfide polymers, polyurethane elasto-mers, chlorosulfonated polyethylene, polychloroprene, plasticized polyvinylchloride using dioctyl phthate or other plasticers well known in the art, butadiene acrylonitrile elastomers, poly(isobutylene-co-isoprene), 20 polyacrylates, polyesters, polyethers, fluoroelastomers, silicone elastomers, thermoplastic elastomers, copoly-mers of ethylene.
Particularly useful elastomers are block copolymers of conjugated dienes and vinyl aromatic monomers.
25 Butadiene and isoprene are preferred conjugated diene elastomers. Styrene, vinyl toluene and t-butyl styrene are preferred conjugated aromatic monomers. Block copolymers incorporating polyisoprene may be hydrogena-ted to produce thermoplastic elastomers having saturated 30 hydrocarbon elastomer segments. The polymers may be simple tri-block copolymers of the type A-B-A, multi-block copolymers of the type (AB),(n=2-10) or radial configuration copolymers of the type R-(BA),(x=3150);
wherein A is a block from a polyvinyl aromatic monomer 35 and B is a block from a conjugated diene elastomer.
Many of these polymers are produced commercially by the Shell Chemical Co. and described in the bulletin "Kraton Thermoplastic Rubber", SC-68-81.

Most preferably, the low modulus elastomeric material consists essentially of at least one of the above-mentioned elastomers. The low modulus elastomeric materials may also include fillers such as carbon black, 5 silica, etc. and may be extended with oils and vul-canized by sulfur, peroxide, metal oxide, or radiation cure systems using methods well known to rubber tech-nologists. Blends of different elastomeric materials may be used together or one or more elastomer materials 10 may be blended with one or more thermoplastics. High density, low density, and linear low density polyethy-lene may be cross-linked to obtain a coating matrix material of appropriate properties, either alone or as blends. In every instance, the modulus of the coating 15 should not exceed about 6000 psi (41,300 kPa), preferably is less than about 5000 psi (34,500 kPa), more preferably is less than 1000 psi (6900 kPa), and most preferably is less than 500 psi (3450 kPa).
A coated yarn can be produced by pulling a group of 20 fibers through the solution of low modulus elastomeric material to substantially coat each of the individual fibers, and then evaporating the solvent to form a coated yarn. The yarn can then be employed to form coated fabrics which in turn, can be used to form 25 desired multilayer fabric structures.
Multilayer fabric articles may be constructed and arranged in a variety of forms. It is convenient to characterize the geometries of such multilayer fabric structures by the geometries of the fibers and then to indicate that substantially no matrix material, elasto-meric or otherwise, occupies the region between fabric layers. One such suitable arrangement is a plurality of layers in which each layer is comprised of coated fibers arranged in a sheet-like array and successive layers of such fabrics are rotated with respect to the previous layer. An example of such multilayer fabric structures is a fine layered structure in which the second, third, fourth and fifth layers are rotated +45, -45, 90 and ~ ~vv 0, with respect to the first layer, but not necessarily in that order. Other examples include multilayer fab-rics with alternating fabric layers rotated 90 with respect to each other.
In various forms of the fabric of the invention, the fiber network occupies different proportions of the total volume of the fabric layer. Preferably, however, the fiber network comprises at least about 50 volume percent of the fabric layer, more preferably between 10 about 70 volume percent, and most preferably at least about 90 volume percent. Similarly, the volume percent of low modulus elastomer in a fabric layer is preferably less than about 15 Vol %, more preferably is less than about 10 Vol ~, and most preferably is less than about 5 15 Vol %.
It has been discovered that coated fabric comprised of strip or ribbon (fiber with an aspect ratio, ratio of fiber width to thickness, of at least about 5) can be even more effective than other forms of fiber or yarn 20 when producing ballistic resistant articles. In parti-cular embodiments of the invention, the aspect ratio of the strip is at least S0, preferably is at least 100 and more preferably is at least 150 for improved perfor-mance. Surprisingly, even though an ECPE strip material 25 had significantly lower tensile properties than the ECPE
yarn material of the same denier but a generally cir-cular cross-section, the ballistic resistance of the coated fabric constructed from ECPE strip was signifi-cantly higher than the ballistic resistance of the 30 coated fabric constructed from the ECPE yarn.
Most screening studies of ballistic composites employ a .22 caliber, non-deforming steel fragment of specified weight (19 grains), hardness and dimensions (Mil-Spec. MIL-P-46593A(ORD)). Limited studies were made employing .22 caliber lead bullets weighing 40 grains. The protective power of a structure is normally expressed by citing the impacting velocity at which 50 of the projectiles are stopped, and is designated the ~2i~3U~

V50 valueO
Usually, a flexible fabric, "soEt" armor is a multiple layer structure. The specific weight of the multilayer fabric article can be expressed in terms of 5 the areal density (AD). This areal density corresponds to the weight per unit area of the multiple layer structure.
To compare structures having different V50 values and different areal densities, the following examples 10 state the ratios of (a) the kinetic energy (Joules) of the projectile at the V50 velocity, to (b) the areal density of the fabric (kg/m2). This ratio is designated as the Specific Energy Absorption (SEA).
The following examples are presented to provide a 15 more complete understanding of the invention. The specific techniques, conditions, materials, proportions and reported data set forth to illustrate the principles of the invention are exemplary and should not be con-strued as limiting the scope of the invention.
EXAMPLE F-l A low areal density (0.1354 kg/m2) plain weave fabric having 70 ends/inch (28 ends/cm) in both the warp and fill direction was prepared from untwisted yarn sized with low molecular weight polyvinylalcohol on a 25 Crompton and Knowles box loom. After weaving, the sizing was removed by washing in hot water (60-72~).
The yarn used for fabric preparation had 19 filaments, yarn denier of 203, modulus of 1304 g/denier, tenacity of 28.4 g/denier, elongation of 3.1% and energy-to-break 30 of 47 J/g. A multilayer fabric target F-l was comprised of 13 layers of fabric and had a total areal density (AD) of 1.76 kg/m2. All yarn tensile properties were measured on an Instron tester using tire cord barrel clamps, gauge length of 10 inches (25.4 cm), and cross-5 head speed of 10 inches/minute (25.4 cm/min).EXAMPLE F-2 Fabric was woven in a similar manner to that used for preparation of fabric F-l, except that a higher 3()0 denier yarn (designated SY-l) having 118 filamellts and approximately 1200 denier, 1250 9 dellier modulus, 30 9 denier tenacity, and 60 J/g energy-to-break) was used to produce a plain weave fabric having areal density of 5 approximately 0.3 kg/m2 and 28 ends/inch (11 ends/cm).
Six layers of this fabric were assembled to prepare a ballistic target F-2.

A 2 x 2 basket weave fabric was prepared from yarn 10 (SY-l) having 34 ends/inch (13.4 ends/cm). The yarn had approximately 1 turn/inch and was woven without sizing. Fabric areal density was 0.434 kg~m2 and a target F-3 was comprised of 12 fabric layers with an areal density of 5.21 kg/m2.

This fabric was prepared in an identical manner to that of Example F-l except that the yarn used had the following propsrties: denier 270, 118 filaments, modulus 700 g/denier, tenacity 20 g/denier and energy-to-break 20 52 J/g. The fabric had ~n areal density of 0.1722 kg/m2. A target F-4 wa~ comprised of 11 layers of this fabric.
_XAMPLE F-5 Yarn SY-l was used to prepare a high denier non-25 crimped fabric in the following manner. Four yarns werecombined to form single yarns of approximately 6000 denier and these yarns were used to form a non-crimped fabric having 28 ends/inch in both the warp and fill direction. Yarn SY-l, having yarn denier of 1200 was 30 used to knit together a multilayer ~tructure. Fabric areal density was 0.705 kg/m2. A ballistic target F-5 was comprised of seven layers of this fabric.
EXAMPLE F-6 (RevlarTM 29) Eight one-foot-square pieces of Kevlar 29 ballistic fabric, manufactured by Clark Schwebel, were assembled to produce a target F-6 having an areal density of 2.32 kg/m2. The fabric was designated Style 713 and was a plain weave fabric comprised of 31 ends per inch of .~ 2 L~ 3 ~.3 i(3 untwisted 1000 denier yarn in both the warp and fill direction.

This sample was substantially identical to sample 5 F-6, except that six layers of Kevla:r 29 were used to produce a target F-7 having a total target areal density of 1.74 kg/m2.
EXAMPLE FB-l Ballisti~ Results Against .22 Caliber Fragments 10 Fabric targets one-foot-square (30.5 cm) and com-prised of multiple layers of fabric were ~ested against .22 caliber fragments to obtain a V50 value. Fabric properties are shown in Table lA and ballistic results are shown in Table lB.

TABLE lA
FABRIC PROPERTIES

Example Yarn Yarn Yarn Weave Denier Modulus Energy- Type (g/den) to-break (J/g) F-l 203 1304 47 Plain F-4 270 700 52 Plain 25 F-2 1200 1250 60 Plain F-3 1200 1250 60 2x2 Basket F-5 6000 1250 60 non-crimped 12~

TABLE lB
Ballistic Results Against 22 Caliber Fragments Sample Fabric AD Target AD V50 SEA
5 No. (kg/m ) (k~/m2? (ft~sec~ (J/m2) F-l 0.1354 1.76 1318 50.5 F-4 0.1722 1.89 951 24.4 F-2 0.316 1.90 116536.9 10 F-3 0.434 5.21 13]817.1 F-5 0.705 4.95 1333 18.0 Sample F-l gave the best ballistic results, sug-gesting that a combination of high modulus yarns and 15 fine weave fabric comprised of low denier ~arn has particular merit.
Example FB-2 Ballistic Results Against .22 Caliber Lead Bullets The striking and exit velocities of 22 caliber lead 20 bullets were recorded. Fabric properties are shown in Table 2A and ballistic results are shown in Table 2B.

Table 2A
-_roperties of Plain Weave Fabrics Example Yarn TypeDenier Modulus Energy-to-Break (g/den.) ( J/g?

30 F-l ECPE 203 1304 47 F-6 Kevlar 29 1000 700 29 F-7 Kevlar 29 1000 700 29 3~0 Table 2B
Ballistlc Results Against .22 Cali~er Bullets Example Fabric AD Target AD V(in) V(out) SEA
(kg/m ) (kg/m2) (Jm2/kg) F-l 0.1354 1.76 1212 0 100.
1198 982 32.2 1194 838 49.5 1193 958 34.6 1171 0 93.8 1148 0 90,2 15 F-7 0.29 1.74 1175 0 95.8 1186 760 57.5 1205 1040 25.5 1176 963 31.6 1216 926 43.1 F-6 0,29 2.23 1198 0 74.6 1214 721 49.6 1181 0 72.5 1200 589 56.9 1181 0 72.5 F-4 0.1722 1.89 1200 1100 1406 1184 1091 13.5 _5 1225 1137 13.2 1144 1037 14.8 30(~

A comparison of the ballistic results of examples F-l and F-4 indicates that higher modulus yarns are much superior for ballistic protection against .22 caliber bullets when woven into a fine weave fabric comprised of 5 low denier yarn. These data also inclicate that the F-l fabric is superior to Kevlar ballistic fabric in current use.
EXAMPLE C-l The individual fabric layers of the target d*s-10 cribed in Example F-l, after ballistic testing against both 22 caliber fragments and .22 caliber bullets, was soaked overnight in a toluene solution of Kraton~ 1107 (50 g/litre). ~raton D1107, a product of ~he Shell Chemical Company, is a triblock copolymer of polysty-15 rene-polyisoprene polystyrene having about 14 weight 4 styrene, a tensile modulus of about 200 psi (measured at 23C) and having a Tg of approx imately -60C. The fabric layers were removed from the solvent and hung in a fume hood to allow the solvent to evaporate. A target 20 C-l, containing 6 wt ~ elastomer, was reassembled with 13 fabric layers for additional ballistic testing.
EXAMPLE C-2A and C-2B
Six one-foot-square fabric layers of the type des-cribed in example F-2 were assembled together and desig-25 nated sample C-2A.
Six fabric lay~rs identical to those of example C-2A, were immersed in a toluene solution of Krato~lG1650 (35 g/litre) for three days and were hung in a fume hood to allow solvent evaporation. Kraton G1650, a triblock 30 thermoplastic elastomer produced by Shell Chemical Co., has the structure polystrene-polyethylenebutylene-polystyrene and has about 29 wt % styrene. Its tensile modulus is abou~ 2000 psi ~measured at 23C), and its Tg is appro~imately -60C. The panel layers each had an areal density of 1.9 ~g/m and contained 1 wt ~ rub-ber. The layers were assembled together for ballistic testing and were designated sample C-2B.

lL~ 0 EX~MPLES C4-C10 Each target in this series was comprised of 6iX
one-foot-square layers of the same fabric, which had been prepared as described in example F-2. The fiber 5 areal density of these targets was 1.90 kg/m2.
Sample C-4 was comprised of untreated fabric~
Sample C-5 was comprised of fabric coated with 5.7 wt ~ Rraton G1650. The fabric layers were soaked in a toluene solution of the Kraton 1650 (65 g/litre) and 10 then assembled after the solvent had been evaporated.
Sample C-6 was prepared in a similar manner to sample C-5 except that after the sample had been dipped and dried, it was redipped to produce a target ha-~ing 11.0 wt % coating.
Sample C-7 was prepared by ~equentially dipping the fabric squares in three solutions of Kraton D1107~dichloromethane to produce a target having 10.8 wt ~ coating. Fabric layers were dried between succe~sive coatings. Concentrations of the Kraton DllO~ thermo-20 plastic, low modulus elastomers in the three coating solutions were 15 g/L, 75 g/L ~nd 15 g/L, in that order.
Sample C-8 was prepared by dipping fabric layers into a colloidal ~ilica solution, prepared by adding three volume parts of de-ionized water to one volume 25 part of Ludox AM, a product of DuPont Corporation which is an agueous colloidal silica dispersion having 30 wt %
silica of average particle size 12 nm and surface area of 230 m2/g.
Sample C-9 was prepared from electron beam irradi-30 ated fabric irradiated under a nitrogen atmosphere to 1Mrad using an Electracurtain apparatus manufactured by Energy Sciences Corporation. The fabric squares were dipped into a Ludox AM solution diluted with an equal volume of deionized water.
Sample Cl~ was prepared in a similar manner to example C-9, except that the fabric was irradiated to 2 Mrads and was subsequently dipped into undiluted LudoxT~-AM. This level of irradiation had no significant effect 3S~O

on yarn tensile poroperties.
EXAMPLE C-ll A plain weave ribbon fabric was prepared from poly-ethylene ribbon 0.64 cm in width, having modulus of 865 5 g/denier and energy-to-break of 46 J/g. Fabric panels (layers) one-foot-square (30.5 cm) were soaked in dich-loromethane solution of Kraton D1107 (lOg/litre) for 24 hours and then removed and dried. The 37 panels, having a total ribbon areal density of 1.99 kg/m2 and 6 wt %
1~ rubber coating were assembled into a multilayer target sample C-ll for ballistic testing.
EXAMPLE CB-l As shown below, the damaged target C-l stopped all 22 caliber bullets fired into it. These results were 15 superior to those obtained for the same fabric before it was rubber coated and much superior to the Kevlar bal-listic fabrics. (See ~xample FB-2.) V(in) V(out) SEA
(ft/sec)_ft/sec)(Jm2/kg) 1218 0 101.5 1182 0 95.6 1172 0 94.0 1159 0 91.9 Although this fabric was highly damaged, a .22 caliber fragment was fired into the target at an impacting velocity of 13Sl ft/sec and was stopped, corresponding to an SEA of 55.5 Jm2/kg. This result indicates that the low modulus rubber coating also improves ballistic resistance against .22 caliber fragments. The V50 value for the uncoated fabric (example F-l) was 1318 ft/sec, corresponding to an SEA
of 50.5 Jm2/kg. The highest partial penetration velocity for Example F-l was 1333 ft/sec, corresponding to an SEA of 51.7 Jm2/kg.

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_ AMPLE CB-2 Targets C-2A and C-2B were marked with a felt pen to divide it into two, 6in X 12in rectangles. The V50 values for each target was determined against .22 cali-5 ber fragments using only one of the rectangles (one halfof the target). Each target was immersed in water for ten minutes, and then hung for three minutes before determination of a V50 value using the undamaged rec-tangle. Data shown below clearly indicate that the 10 small ammount of rubber coating has a beneficial effect on the ballistic performance of the fabric target when wet.

V50 (ft/sec) Target C-2A Target C-2B
(untreated)_ (1 wt % Elastomer) (Ballistic Studies using 28x28 plain weave, coated fabrics) Ballistic testing using .22 caliber fragments 25 against six-layer fabric targets having fiber areal den-sity of 1.90 kg/m2 showed that elastomeric coatings improved ballistic performance, but silica coatings were ineffective.

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Sample Coating V50 SEA
(ft/sec) (Jm2/kg) _ C-4 none 1165 36.9 5 C-5 Kraton G1650 1228 41.0 (5.7 wt %) C-6 Kraton G1650 1293 45.4 (11 wt %) C-7 Kraton D1107 1259 43.1 (10.8 wt %) C-8 Silica 1182 38.0 (3.4 wt ~) c-9 Silica 1150 36.0 (7.2 ~It %) 1 C-10 Silica 1147 35.8 (17 wt %) Sample C-ll was tested ballistically and exhibited 20 a V50 value of 1156 ft/sec determined against 22 caliber fragments. This corresponded to a SEA value of 34.4 Jm2/kg. This target exhibited good ballistic properties in spite of the fact that ribbon stress-strain proper-ties were inferior to those of most of the ECPE yarns used in this study.
A V50 value of 1170 ft/sec against .22 caliber bullets was obtained for example C-ll, whereas samples C-5, C-6 and C-7 allowed bullets having striking velocity of approximately 1150 ft/sec to pass through the target with velocity loss of less than 250 ft/sec.
This indicates that the ribbon fabric is particularly effective against .22 caliber lead bullets.
Having thus described the invention in rather full detail, it will be understood that these details need not be strictly adhered to but that various changes and modifications may suggest themselves to one skilled in the art, all falling within the scope of the invention as defined by the subjoined claims.

Claims (16)

WE CLAIM:

1. An article of manufacture, comprising:
a) at least one network comprising fibers selected from the group of extended chain polyolefin fibers, extended chain polyvinyl alcohol fibers and extended chain poly acrylonitrile fibers; and b) a low modulus elastomeric material which substantially coats said fibers and has a tensile modulus (measured at 23°C) of less than about 6,000 psi (41,300 kPa).

2. An article as recited in claim 1, wherein said fibers have a tensile modulus of at least about 1000 g/denier and an energy-to-break of at least 50 J/g.

3. An article as recited in claim 1, wherein said elastomeric material comprises an elastomer having a glass transition temperature of less than about 0°C.

4. An article as recited in claim 1, wherein said elastomeric material has a tensile modulus of less than about 1,000 psi.

5. An article as recited in claim 1, wherein said fibers are ECPE fibers having a weight average molecular weight of at least about 500,000 and a tenacity of at least about 15 g/denier.

6. An article as recited in claim 5, wherein said layers have an arrangement in which the fiber alignment directions in selected layers are rotated with respect to the fiber alignment direction of another layer.

7. An article as recited in claim 1, wherein said low modulus elastomeric material comprises less than about 10 vol % of each coated fiber network.

8. An article as recited in claim 1, wherein said network of fibers is comprised of high molecular weight, extended chain polyethylene strips.

9. An article as recited in claim 1 wherein the coating comprises between about 0.1 and about 30% (by weight of fibers) of the coated fiber network.

10. An article as recited in claim 1 wherein the aspect ratio of the fiber is at least about 5:1.

11. An article as recited in claim 1 wherein the fiber comprises at least about 70% by volume of the coated fiber network.

12. A fiber comprising a polymer having a weight average molecular weight of at least about 500,000, a modulus of at least about 200 g/denier and a tenacity of at least about 10 g/denier and coated with an elasto-meric material having a tensile modulus (measured at about 25°C) not greater than about 6000 psi.

13. The fiber of claim 12 wherein the coating is between about 0.1 and about 60% by weight of the fiber.

14. The fiber of claim 12 wherein the fiber has an aspect ratio of at least about 5:1.

15. The fiber of claim 12 wherein said polymer is selected from the group of polyolefin fiber, poly-acrylonitrile fiber and polyvinyl alcohol fiber.

16. The fiber of claim 15 wherein the elastomeric material consists essentially of an elastomer.