WO2008105929A2

WO2008105929A2 - Method of forming adhesive mixtures and ballistic composites utilizing the same

Info

Publication number: WO2008105929A2
Application number: PCT/US2007/077966
Authority: WO
Inventors: Addison W. Closson
Original assignee: Closson Addison W
Priority date: 2006-09-08
Filing date: 2007-09-10
Publication date: 2008-09-04
Also published as: WO2008105929A3

Abstract

The invention relates to adhesive compositions used in composite laminar structures to improve ballistic resistance, for example, which limits the penetration of a bullet from a gun. The composite laminar structures includes composite laminar structure, includes an aramid or olefin fiber layer, a eutectic impact absorbing adhesive resin or adhesive composition layer, and an ionomer layer. The aramid or olefin fiber layer is adhesively bonded with the eutectic impact absorbing adhesive resin or adhesive composition layer to the ionomer layer. In further embodiments, the composite laminar structure includes an olefin fiber layer, a eutectic amorphous acid functional polypropylene copolymer adhesive layer, and an ionomer layer. The olefin fiber layer is adhesively bonded with the eutectic amorphous acid functional polypropylene copolymer adhesive layer to the ionomer layer. The olefin fiber layer has no polarity within a matrix thereof and has no affinity for moisture.

Description

METHOD OF FORMING ADHESIVE MIXTURES AND BALLISTIC COMPOSITES UTILIZING THE SAME

BACKGROUND OF THE INVENTION FIELD OF THE INVENTION

[0001] This invention relates to an impact absorbing adhesive resin, which improves ballistic resistance of ballistic substrates by coating or forming composites of ballistic substrate with the impact absorbing resin. The invention also relates to a composite laminar structure of a ballistic substrate with an impact absorbing resin.

BACKGROUND OF THE INVENTION

[0002] This invention is directed to providing ballistic protection, e.g., ballistic protection (armor) for combat soldiers. The invention relates to a ballistic substrate, such as polyaramid and/or attenuated olefinic fibers or plies formed into composite laminar structures and having improved ballistic impact resistance an impact and/or puncture resistant adhesive resin used to laminate that ballistic substrate. The composite laminar structure may be used in a wide variety of applications, e.g., in protective body armor or helmets such as those used by crew members as well as shielding on combat vehicles, and aircraft or used by foot soldiers. The impact absorbing adhesive resin used to bond the ballistic substrates into a composite laminar structure may also be used to bond metal or ceramic panels to the ballistic substrates or on motor vehicles or aircraft (e.g. door panels, roofs, etc.) to increase the ballistic resistance of these panels. The invention also relates to a process for making composite laminar structures, body armor, helmets, etc. and to methods for improving ballistic resistance of metal or ceramic panels on motor vehicles or aircraft.

[0003] A long standing problem of the related art is to provide a helmet which can be worn comfortably by combat soldiers while providing the requisite protection from projectiles (i.e., ballistic resistance). Such a helmet should afford the wearer with the greatest ballistic protection possible, but this protection must be accomplished in headgear which is not unduly heavy, fits various size heads, and will not interfere with the required activities of the wearer and which may be worn with relative comfort for long periods of time. At the present time, helmets must have a minimum resistance to bullets— no penetration and not more than 44 mm indentation. Currently, helmets are made from polyaramid, e.g., Kevlar^®, woven fibers generally having from 10 to 60 woven or non- woven fiber layers (plies) alternating with adhesive layers which adhere the adjacent plies together. The adhered plies can be positioned within a thin helmet shell such as a polyester, epoxy, polyvinylbutyral prepreg thermoset (phenolic) or polyvinyl ester prepreg thermoset shell. The number of plies used to make a protective helmet is limited by the weight a combat soldier can comfortably support on his head (currently about 3 lbs.).

[0004] Another problem of the prior art is that the conventional processing of Kelvar^® is expensive and time intensive. For example, in the prior art a Kevlar^® cloth thermosetting prepeg needs about 20-30 minute cure times in order to form a ballistic composite. The prepreg is difficult to work with as it has limited shelf life and needs be kept cold. As a result, because of the cure time the production rates are slow and manufacturing is expensive.

[0005] Accordingly, it is desirable to provide a composite laminar structure which is light weight with excellent resistance against ballistic impact while also being easily manufactured, e.g., needing less heat, pressure, and/or time in the manufacturing process. Moreover, there is a need to provide an improved composite laminar structure, e.g., a protective helmet having a higher resistance against ballistic impact than is presently available from protective helmets having the same or greater weight. Such a helmet should meet or exceed the present requirements of weight and resistance to ballistic impact for protective helmets.

SUMMARY OF THE INVENTION

[0006J The invention is based upon the discovery that one or more ionomer layers adhesively bonded with an impact absorbing adhesive resin layer to a ballistic substrate improves ballistic resistance of the ballistic substrate. Advantageously, the exemplary embodiment provide adhesive compositions used in composite laminar structures to improve ballistic resistance, for example, which limits the penetration of a bullet from a gun.

[0007] In an exemplary embodiment, there is provided a composite laminar structure, including an aramid or olefin fiber layer, a eutectic impact absorbing adhesive resin or adhesive composition layer, and an ionomer layer. The aramid or olefin fiber layer is adhesively bonded with the eutectic impact absorbing adhesive resin or adhesive composition layer to the ionomer layer.

[0008] In a further exemplary embodiment, there is provided a composite laminar structure, including an olefin fiber layer, a eutectic amorphous acid functional polypropylene copolymer adhesive layer, and an ionomer layer. The olefin fiber layer is adhesively bonded with the eutectic amorphous acid functional polypropylene copolymer adhesive layer to the ionomer layer.

[0009 J In a further exemplary embodiment, in the composite laminar structure, the olefin fiber layer has no polarity within a matrix thereof and has no affinity for moisture.

[0010] In further exemplary embodiments, there is provided a method of making the composite laminar structures of the exemplary embodiments.

[0011] In further exemplary embodiments, the composite laminar structures of the exemplary embodiments are in the form of body armor, shielding, helmet, vehicle, or aircraft.

[0012] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

[00131 Aspects of the invention are illustrated in the figures of the accompanying drawings and in which like reference numerals refer to similar elements and in which:

[0014] FIGS. IA and IB illustrate preparing a composite substrate with an olefin hot melt adhesive composition containing polar pendants and acid functional sites.

[0015] FIG. 2 illustrates a flow diagram of a process to form a composite laminar structure.

[0016] FIG. 3 illustrates a modulated differential scanning calorimeter (DSC) chart of a hot melt adhesive composition.

[0017] FIG. 4 illustrates a viscosity diagram of a hot melt adhesive composition.

[0018] FIGS, 5-6 illustrate composite substrates with ionomer and hot melt adhesive compositions according to further embodiments of the invention.

[0019] FIG. 7 illustrates a composite substrate with ionomer and adhesive compositions according to further embodiments of the invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] The exemplary embodiments include an adhesive composition, e.g., a hot melt adhesive composition, utilized to adhere ballistic substrates, such as adjacently positioned ballistic substrates, such as polyaramid plies. The resulting composite laminar structure has markedly improved resistance to ballistic impact. A polyaramid composite laminar structure can be shaped thermoplastically (as opposed to having to be cured using a thermoset resin), for example, into body armor, a helmet or other desired shielding shapes using a male/female molding technique. Alternatively the composite laminar structures, e.g. polyaramid composite laminar structures, can be applied to metal used both to bond ceramic panels, e.g., strike faces on motor vehicles, such as a Humvee, or in aircraft, such as helicopters or fixed wing, thereby improving the ballistic resistance (e.g., by fracturing and dissipating momentum).

10021] In the invention, an impact absorbing adhesive resin is used to improve the ballistic resistance of ballistic substrates by forming composite laminar structure with the impact absorbing adhesive resin. The ballistic substrates include woven or non-woven cloth or fiber materials, such as polyaramid fibers including organic filaments composed of aramid fibers (e.g., aromatic polyamide), for example, Kevlar^®, Heracron, or Twaron aramids. The substrates may include, for example, poly(m-xylylene adipamide), poly(p-xylylelene sebacamide), poly(2,2,2-trimethyl-hexamethylene terephthalamide), poly(ρiρerazine sebacamide), poly(metaphenylene isophthal amide) (Nomex) and poly(p-phenylene terephthalamide) (Kevlar^®) or an oriented/attenuated fibers like olefin fibers (Spectra^®, Dyneema^®). Also, the substrates may include ZYLON^®, which consists of rigid-rod chain molecules of ρoly(p-ρhenylene-2,6-benzobisoxazole)(PBO). Other suitable ballistic substrates as known in the art may also be used. Moreover, any combinations of these ballistic substrates may be used and these substrates can be, and are, manufactured in a wide variety of styles. For example, the materials may be woven or non-woven or combinations thereof. Also available are non-fabric materials, such as metals, ceramics, or other composite materials.

[0022] The polyaramid fibers utilized to form the cloth plies can also be coated with metal, e.g., copper coated fibers such as disclosed by U.S. Patents 5,935,706 and 6,045,680 which are incorporated by reference. The cloth plies are formed from fibers comprising threads having a denier between about 1000 and about 6000 preferably between 1500 and about 4000. A typical thread density is between about 10 and 150 threads per inch. Non woven cloth plies can also be used.

[0023] An exemplary Kevlar^® material weave pattern is either a plain or a satin weave or any comparable weave or non-woven random or linear fibers that has high conformity to draping over complex shapes. However, a "plain" weave is very suitable for molding. An exemplary thickness of the cloth material is from about 0.006 inch to about 0.060 inch. The woven composite fabric or cloth is available from a number of sources including ICI Fiberite of Tucson, Ariz., Hexcel Corporation of Dublin, BGF Industries, Inc. of Greensboro, ISI .C, Warwick Mills of New Ipswich, N.H., Lincoln Fabrics of Geneva, Alabama, Barday, Cambridge, Ontario Canada, and others. Again, any Kevlar^® or Spectra^® fabric may be used to make a composite laminar structure of the invention. By way of example, Kevlar^® material sold by Hexcel Schwebel Corporation under the category Advanced Composite Fabrics and which is useful in the invention is Kevlar^® 29. The Kevlar^® 29 fabric used was about 0.020 inches thick, and weighs about 12 oz/sq. yard, has about 3000 denier with a 15 x 15 thread count. Other useful polyaramid fabrics include Twaron high tenacity, Kevlar^® 129 fabric and Kevlar^® 9-5000 fabric has a 5H-Satin weave, 13.0 Mils thickness, yarn type K49/2160 DN warp and fill, 17x17 count, 9.00 oz./yard², and breaking strength of 920 lbs./inch warp and 970 lbs./inch fill.

[0024] The impact absorbing adhesive resin component is a medium to low melt index, low modulus acid resin. The impact absorbing resins preferably have a melt index between about 1 and about 100, preferably between about 2 to 40, and more preferably between about 2 to 25. The flexural modulus of the impact absorbing adhesive resin preferably ranges from between about 2000 to 8000 psi, and more preferably between about 2500 to 6300 psi. In a preferred embodiment, the impact absorbing adhesive resin has a solubility parameter, δ. (the square root of cohesive energy density), from about 15 to 22 J^I/2/cm^3/4. For a discussion of solubility parameters and cohesive energy, see Chapter 7, COHESIVE PROPERTIES AND SOLUBILITY, in KREVELEN, D.W. van, "PROPERTIES OF POLYMERS: Their Correlation With Chemical Structure," Third Ed, Completely Revised Edition, 1997, XXII + 875 pp., ISBN: 0-444-82877-X, which is incorporated by reference. For example, the solubility parameter for polyethylene ranges from 15.8 to 17.1 J^1/2/cm^3/4, and for poly(methyl acrylate) ranges from 19.9 to 21.3 J^1/2/cm^3/4. Exemplary impact absorbing adhesive resins include olefin-acrylic acid copolymers, olefm- methacrylic acid copolymers, olefin-maleic anhydride copolymers, olefin-acrylic acid- acrylate terpolymers, olefm-methacrylic acid-acrylate terpolymers, olefin-acrylic acid- methacrylate teφolymers, olefin-methacrylic acid-methacrylate terpolymers, olefin-maleic anhydride acrylate terpolymers, olefin-maleic anhydride methyacrylate terpolymers, and mixtures of such resins. The olefinic monomer may be a Cj-C₆ olefin, preferably ethylene or propylene. Representative suitable impact absorbing adhesive resins include ethylene - acrylic acid - methyl acrylate teφolymers; ethylene-acrylic acid copolymers, n-butyl acrylate - acrylic acid - maleic anhydride terpolymers, or the like. Non polar amoφhous polypropylene co polymers / ter polymers can be chosen for olefin armor fibers.

[0025] Impact absorbing adhesive resins useful in the invention are those which improve toughness, flexibility and adhesion characteristics of materials or substrates. Preferred impact absorbing adhesive resins are those which are also useful as heat activated seals, adhesion promoter (e.g., bipolar adhesion promoters) in polyolefin compounds, engineering thermoplastic impact modifier, and hot melt adhesives. A number of different commercially available copolymers and teφolymer resins products may be used, for example, Dow's PrimaCore, Exxon's Escor resins, and DuPont Elvax acid teφolymer resins among others. Additional components to the impact absorbing adhesive resin can also be included, such as, antioxidants, UV inhibitors, flame retardants, reinforcing fillers, and the like as known in the art. Typically these additional components are present in amounts of about 0.1 to 20 parts by weight.

[0026] A particularly preferred class of ethylene - acrylic acid - acrylate teφolymers which are useful as the impact absorbing adhesive resins include resins having about 6% acrylic acid monomer and about 20% acrylate monomers (e.g., methyl acrylate, ethyl acrylate, n-butyl acrylate, and propyl acrylate). The acid monomers add to ionic bonding capabilities of the resin and as such, increasing the number of acid monomers increases the ability to adhere to inorganic substrates. The esters monomers also add increased polarity to the resin and also provide improved adhesion to organic substrates (e.g., polar organic substrates). As the ester side chain increases in length or branching (e.g., methyl to butyl) the polarity of the ester monomer decreases allowing the adhesive properties of the resin to be adjusted for particular uses. Also, the higher the acrylate ester content the higher the polar interfaces for bonding to polar substrates, thereby providing improved adhesion. [0027] The Exxon Escor resins are preferred impact absorbing adhesive resins to be used in this invention. A preferred Exxon Escor resins is Exxon Escor AT 325, an ethylene methyl acrylate acrylic acid terpolymer at a composition of about 74% ethylene, 20% methyl acrylate, 6% acrylic acid. The Escor resins are acid terpolymers from a family of methyl acrylate acrylic acid terpolymers that adhere well via the ethylene chain to a number of non- polar materials such as polypropylene, polyethylene and ethylene-propylene diene rubber, as well as to polar materials like aramids, polyamides and polyesters. These resins have a shore hardness, scale A (15S) between about 50-90 via ASTM D2240, as known in the art. Also, the resins adhere well to metals and glass via the resins acid functionality. The Escor AT 325 terpolymer has a melt index of about 20 g/10 min based on ASTM D1238; a vicat softening point of about 101⁰F based on ASTM D 1525; and a flexural modulus at about 2680 psi based on ASTM D790 as known in the art.

[0028] One embodiment of the invention is directed towards forming a ballistic substrate composite or forming layered structure having a resin layer coated on a release sheet (e.g., silicon release paper) with the impact absorbing adhesive resin or an adhesive composition containing the impact absorbing adhesive resin, described below. That is, forming a layered structure and for ease of manufacturing the adhesive layer may be sandwiched between two release layers, which may be removed sequentially for application to a ballistic substrate. To form the composite laminar structure, the impact absorbing adhesive resin or a an adhesive composition containing it is coated on one surface of the ballistic substrate. Additional layers of the ballistic substrate may be applied to the exposed coating. The composite laminar structure may be built using layers of ballistic substrate and adhesive resin. An exposed layer of the adhesive resin may be used to adhere the ballistic substrate to a surface to be protected by the ballistic composite laminar structure, hi one configuration, the embodiment includes applying a coating of the impact absorbing adhesive resin onto a release sheet which may then be applied to a ballistic substrate or other surface with heat and/or pressure. The release sheet may be removed before, during, or after that application to expose the adhesive resin.

[0029] In another embodiment, the impact absorbing adhesive resin is formulated with one or more resins into an adhesive composition, preferably a hot melt adhesive composition, used for coating the ballistic materials. The composition is designed to provide for better wetting out of surface areas, flow with less heat and/or pressure than a pure copolymer or terpolymer neat film. In this embodiment, the impact absorbing adhesive resin is formulated as an adhesive composition including five components as follows:

[0030] (1) Between about 20 and 90 weight percent of an impact absorbing adhesive resin, discussed above, and more preferably between about 35 to 55 weight percent. For example, an acrylic acid or methacrylic acid olefinic copolymer or terpolymer having a melt index between about 1 to 100, preferably between about 5 to 40 and having an acid number of 10 or higher. A preferred ethylene acrylic acid or methyl acrylate acid terpolymer is selected an Exxon Escor resins, and particularly preferred is Exxon Escor AT 325 resin.

[0031] (2) Between about 30 to 70 weight percent of an olefinic (meth) acrylate

(acrylate or methacrylate) copolymer or olefinic vinyl acetate copolymer each having a melt index between about 0.5 to 100, preferably between about 2 to 30. More preferably, the weight percent is between about 15 to 35. The olefinic monomer may be a C]-C₆ olefin, preferably ethylene or propylene. In a preferred embodiment, the olefin (meth)acrylate resin has a solubility parameter, δ, (the square root of cohesive energy density), from about 15 to 26 J^i/2/cm^3/4. For example, the solubility parameter for polyethylene ranges from 15.8 to 17.1 J^i/2/cm^3/4, for poly(methyl acrylate) ranges from 19.9 to 21.3 J^1/2/cm^3/4, and for poly(methyl methacrylate) ranges from 18.6 to 26.2 J^1/2/cm^3/4. Representative copolymers include polymerized ethylene-methyl acrylate; polymerized ethylene-methacrylate, n-butyl acrylate; butyl-, ethyl-, and methyl acrylate (EBA, EEA, and EMA) copolymers, and the like. More preferably, the acrylate monomers have a solubility parameter ranging between about 18.5 to 26. Also, methyl vinyl acetate (MVA), ethyl vinyl acetate (EVA), propyl vinyl acetate (PVA), and butyl vinyl acetate (BVA) copolymers may be added or used.

[0032] A preferred olefin-(meth)acrylate copolymer includes from about 15 to 35% methyl acrylate. A preferred commercially available product is olefinic methyl acrylate copolymer such as Exxon's Optema products. These copolymers have a melt index between about 1.0 to 100 via ASTM D1238; a flexural modulus between about 2500 to 6000 psi via D790; a vicat softening point between about 90 to 130 ⁰F via D 1525; and a shore hardness, scale A (15S) between about 70 to 90 via ASTM D2240, as known in the art. A particularly preferred Optema copolymer is Exxon's Optema TC-221 or TC-220, ethylene-methyl acrylate copolymers with about 27% methyl acrylate. The ethylene methyl acrylate (EMA) is a very thermally stable high-pressure PE copolymer. It can be processed by conventional thermoplastic processing methods including extrusion coating laminating, blow/cast monolayer and coextruded films, injection molding, sheet or profile extrusion, blow molding and foam extrusion. Moreover, it can be used for making alloys, blends, and compounds, or be extruded where softness and flexibility are required. The applications also include a coextruded tie layer for flexible packaging applications, compatϊbilzer or impact modifier for engineering thermoplastics, hot melt adhesives, sealants, and the like.

[0033] Component (2) of the adhesive composition may also be or include an olefinic ethylene vinyl acetate copolymer. The vinyl acetate monomer may be methyl vinyl acetate (MVA), ethyl vinyl acetate (EVA), propyl vinyl acetate (PVA), and butyl vinyl acetate (BVA). Preferred olefinic ethylene vinyl acetate copolymers are commercially available as DuPont's Evaloy AC resins, which have about 15 to 28 weight percent vinyl acetate monomer; a vicat softening point between about 100 to 200 ⁰F via ASTM Dl 525; and a melt index between about 1 to 10.0 g/10 min. via ASTM D1238 as known in the art.

[0034] A preferred olefinic vinyl acetate copolymer is ethylene vinyl acetate copolymer and acid terpolymer. These copolymers may be added to the mixture or used independently as component (2). In use they aid to increase adhesion to polycarbonate materials, ceramic tile materials, aromatic and aliphatic urethanes, polymers, ABS, metal, and the like. Some commercially available ethylene vinyl acetate copolymers include Dupont's Elvax resins. More preferably Dupont's Elvax 4210 and 4260. These EVA terpolymers have 28% by weight vinyl acetate and methacrylic acid groups, with a melt index of about 5 g/10 min to 500 g/10 via ASTM D 1238; and a softening point ring ball between about 140 to 350 ⁰F via ASTM E28.

{0035] (3) Between about 3 and 40 weight percent of an acid rosin such as Tall oil rosin, gum rosin, or wood rosin. More preferably, the weight percent is between 15 to 40. The acid rosin has an acid number between about 20 to 200, preferably between about 100 to 160, and a melt temperature between about 60 to 130 ⁰C, preferably between about 65 to 100⁰C. A preferred acid rosin is a Tall oil rosin such as Unitac rosin available from Union Camp or Arizona, Stabilite gum rosin and Foral AX hydrogenated rosin for optical reasons in conjunction with ionomers, both rosins from Hercules, may also be used.

[0036] (4) Between about 1 to 20 weight percent of a high melt oxidized wax having a melting point between about 80 to 120⁰C, preferably between about 95 to 125°C, and an acid number between about 5 to 50. More preferably, the weight percent is between about 5 to 15. Representative suitable oxidized waxes include oxidized high density polyethylene, oxidized microcrystalline amber wax, oxidized fischer Trope wax oxidized parafinic wax or the like. A preferred wax is Marcus Wax 3500, which has a softening point of about 235 ⁰F, an acid no. of 24, and a specific gravity of about 0.97. Marcus Wax 3500 is available from Marcus Chemical, Houston, Texas.

(0037] (5) Between about 1 and 20 weight percent of a low melt wax having a melting point between about 55 to 90⁰C, preferably between about 59°C to 70⁰C, and an acid number between about 10 and about 100. More preferably, the weight percent is between about 5 to 15. The low melt wax may be either compatible or non-compatible with the other resins of the adhesion composition. Representative suitable low melt waxes include long chain fatty acid alcohols, esters, or amids, including but not limited to triple pressed stearic acid, oleic acid ester, stearamide or the like when melted. Preferably, the low melt wax is a triple pressed stearic acid having a softening point ranging from about 130 to 150 ⁰F and/or low to high density polyethylene with a low softening point in a ranging from about 85 to 115 ⁰C.

[0038] The low melt may act as an external plasticizing oil-like lubricant (in contrast to a solvating lubricant). The low melt wax enables resin to flow sooner and easier without lowering the vicat or creep temperature and acts as an antiblocking agent by surface blooming as known in the art. It also allows the adhesive to melt at less than the boiling point of water preventing pockets of delamination caused by steam ,

[0039] Additional components to the above can be included in the adhesive composition such as antioxidants, UV inhibitors, flame retardants, reinforcing energy absorbing fillers, and the like as known in the art. Typically these additional components are present in amounts of about 0.1 to 20 parts by weight.

[0040] The adhesive compositions used in the invention may be made using techniques known in the art. For example, in an embodiment, the adhesive may be made in a heated mixer with a sigma blade or in a hot kettle with an agitator. It can also be blended in an extruder using a static mixer in the adaptor or at the mixing head extruder screws (e.g., Madox head) will blend adhesives in extrusion, as known in the art. Typical mixing temperatures range from about 250 to 400 ⁰F, of course these temperatures are dependent upon the properties (e.g., viscosity) of ingredient components as would be understood by one skilled in the art. The polymer components (1) and (2) may be mixed together first then combined with the remaining components. Alternatively, an adhesive composition of the invention may be prepared by extruding the components using, for example, a single or twin screw mixer extruder,

[0041] An adhesive composition used in the invention has an acid number greater than 5 and preferably ranging from about 50 to 140. In a preferred embodiment, the copolymers (1) and (2) described above have solubility parameters of ranging from about 18 to 25. Containing solvating waxes and tackifiers, adhesive compositions of the invention demonstrate some super cooling and suspended transformation effects which gives longer pressure sensitivity and open tack time when exposed to heat in excess of about 150⁰F. This makes them suitable for hot melt adhesive applications. The adhesive compositions of the invention also possess better long term resistance to aromatic and aliphatic oil because of the higher polarity of the polar pendants.

[0042] The adhesive compositions used in the invention have, advantageously, having a bonding strength at about 6-20 lbs per 1 inch width tensile test strength when used to bond 1" strips of Kevlar^® when tested at room temperature. The adhesive compositions also bond to Spectra® or Kevlar^® cloth to standard ceramic ballistic armor at about 6-20 lbs per 1" strip tensile pull. The adhesive compositions of the invention also bond Kevlar^® to Spectra^® at about 6-20 lbs per 1" tensile pull and can be bonded at between about 220 to 245°F so not to impair the linear orientation of the Spectra^® fibers. Most advantageously, the adhesive compositions can bond Spectra^® to Kevlar^® or to ceramic and metal in the same laminate at about 245°F or less, preferably at about 220⁰F.

[0043] Although not intending to be bound by theory, it is believed that the impact absorbing adhesive resin and adhesive compositions of the invention melts, to some extent, upon impact of a projectile to allow the ballistic substrate (particularly textile or fabric ballistic substrates such as Kevlar^®) to give way and become more linear in the direction of the projectile trajectory in order to absorb more energy. This stretching during impact occurs both because of the adhesive 's low modulus to allow the textile substrate to attenuate and because the adhesive begins to stretch and melt upon projectile impact. Thus, it is believed, that the impact absorbing adhesive resin and adhesive compositions absorb energy in the milliseconds between impact and penetration by changing from an amorphous structure to a linear structure and by a complex phase transformation from a solid to a liquid/melted state. The related present day art composites are thought not to melt and/or stretch upon impact, but rather break or shear and thus have poorer ballistic resistance.

[0044] The composite laminar structures, e.g.. polyaramid laminar structures, of this invention is made by positioning the impact absorbing adhesive resin or adhesive composition between adjacent layers of ballistic substrates, e.g., plies of polyaramid fabric, usually between about 5 and 100 layers or fabric plies, preferably between about 9 and about 65 layers or fabric plies. The impact absorbing adhesive resin is coated or applied to the substrate by melting the adhesive composition and applying it on one side as a continuous or non-continuous layer or printing dots at intervals positioned between about Vs to % inches from each other, preferably between about % to ¹A inches from each other. The adhesive layer continuous dots are between about 0.0002 to 0.020 inches thick, preferably between about 0.0004 to 0.005 inches thick. Other known methods of applying the adhesive layer which may be used are mentioned below. Also, as mentioned above, the adhesive may also be applied from a layered structure having the adhesive coated onto a release sheet (as a continuous layer or dots). The ballistic substrate can be applied to the exposed adhesive layer and the release sheet removed to apply a subsequent ballistic substrate.

[0045] A preferred composite laminar structure of this invention is formed of woven or non- woven polyaramid fibers, e.g., Kevlar^® available from E. I. DuPont de Nemours. The laminated composite laminar structure of this invention comprises polyaramid fabric plies having interposed therebetween them layers of an impact absorbing adhesive resin or adhesive composition of this invention. The impact absorbing adhesive resin/adhesive composition layers fill the interstices between the threads and adhere adjacently positioned plies. In a preferred embodiment the composite has about 12 to 20 polyaramid plies with about 12 to 20 impact absorbing adhesive resin/adhesive composition layers. Typically the composite is manufactured by coating one side of each ply and adhering the coated side to the uncoated side of the next ply. Alternatively, both sides of a ply may be coated with the adhesive. The thickness of the impact absorbing adhesive resin/adhesive composition layer can range from about 0.0005 to 0.030 inches and coated with about 0.003 inches on one side. When tested with a bullet 16' from a barrel of a 44 Magnum Remington, the bullet penetration in the composite laminar structure 10 is 32 mm or less, and tested as low as 16 mm with a composite laminar structure having 12 plies. [0046J The composite laminar structure may also be used as shielding and applied to plastic, ceramic, or metal panels by heating the panels to a temperature sufficient to soften or melt the impact absorbing adhesive resin of the composite laminar structure (about 245°F) and then pressing it onto the panel. Alternatively, the composite laminar structure may be placed on the panel and then both heated to adhere the impact absorbing adhesive resin coated laminar structure to the metal or ceramic panel. Convection, autoclave, and/or microwave heating may be used. It is preferred that the composite laminar structure be cut to cover the shape of the panel to which it is being applied. An exposed layer of the impact absorbing adhesive/adhesive composition may be used to bond the composite laminar structure. In one embodiment, the composite laminar structure may be built upon a layered structure having a release sheet on top or bottom with the release sheet remaining in place during manufacture. The release sheet may then be removed to prevent bonding to the metal mold or expose an adhesive layer for subsequent bonding to another substrate.

10047] One advantage of the impact absorbing adhesive resins and preferably, the hot melt adhesive compositions, of the invention is that they adhere ballistic substrates such as Kevlar^® or Spectra^® to both metal and ceramic panels providing ballistic protection in body armor, shields, helmets, vehicles, and the like. The shielding may be dimensioned to be able to carry on the arm and include windows. Ballistic resistant ceramics may include silicone carbide, boron carbide, phase transformation alumina and other oxide ceramics. When used with ceramic panels the composite laminar structure of the invention is preferably applied between the vehicle and the ceramic panel. The ceramic panel causes an energy absorbing effect on impact and the composite laminar structure of the invention absorbs the remaining ballistic impact. The ballistic ceramics may include silicone carbide, boron carbide phase transformation alumina and other oxide ceramics. Metals and alloys may also be bonded, such as aluminum, steal, etc.

[0048] FIGS. IA and IB illustrate preparing a composite laminar structure with a hot melt adhesive composition according to an embodiment of the invention. The other composite laminar structures of the invention described above may be similarly prepared.

[0049] In this embodiment, the impact absorbing adhesive resin is a formulated hot melt adhesive composition as described above, which is applied to at least one ballistic substrate to form a composite laminar structure. The hot melt adhesive composition may be applied using techniques known in the art, for example it may be extruded, knife coated, roller coated, and printed as continuous dots or in other patterns such as cross hatch patterns or lines as well as a continuous film onto the ballistic substrate. Other conventional application techniques such as sintering or laminating from a release sheet as known in the art are also possible. Now referring to FIG. IA, at least one ballistic substrate 105 is applied with hot melt adhesive composition by at least one of roller coated, printed, extruded or other conventional techniques. Optionally, additional ballistic substrates, for example, additional plies of ballistic substrates 1 10, 115, and 120 may also be covered with the hot melt adhesive composition. These ballistic substrates may be any combination of materials as described in detail above. Moreover, the number of ballistic substrates is optional, in one embodiment, the number of plies of polyaramid fabric ranges from about 5 to 250 plies. The ballistic substrates may be heated via a conventional apparatus 125, for example, heated in an oven, microwave, autoclave, steam, and combinations thereof.

[0050] Optionally, as shown in FIG. IB, the ballistic substrates may be placed in a flexible vacuum bag 130 under a vacuum pressure or other suitable device for applying a pressure force. The vacuum pressure may be in the range near atmospheric pressure or at a higher or lower pressure, hi this embodiment, a ceramic like tile 135 is adhered to the other ballistic substrates 140, 145, and 150. The order of applying the hot melt adhesive to the various ballistic substrates is optional and based upon manufacturing desires. For example, the ceramic like tile 135 is arranged preformed composite laminar structure. In this configuration, the preformed composite laminar structure is the ballistic substrates (e.g., 140, 145, and 150) applied with hot melt adhesive composition and allowed to cool. Alternatively, the entire composite laminar structure may be formed in-situ. In operation, the vacuum bag allows for pressure to be controlled (e.g., above or below atmospheric pressure) and applied to the composite laminar structures.

(0051] In another exemplary embodiment, an adhesive release sheet is coated with an impact absorbing adhesive resin for use with forming composite laminar structures from ballistic substrate materials.

[0052] FIG. 2 illustrates a flow diagram of a neat process to form composite laminar structures. In this embodiment, the impact absorbing adhesive resin is an acrylic acid or methacrylic acid olefinic co-polymer or terpolymer having a melt index between about 1 and about 100, preferably between about 5 and about 40. Referring to FIG. 2, in step 210, the impact absorbing adhesive resin is placed into an ex trader. In this embodiment, the impact absorbing resin is preferably, an acrylic acid methyl acrylate terpolymer, e.g., Escor AT 325.

[0053] In step 215, the appropriate die is adjusted for the desired application (e.g., the width and thickness of the die is adjusted). By way of illustration, a die may be selected to have a size being about 0.005 inches to 75.0 inches or greater in width and a desired extruded thickness of about 0.0003 to 0.050 inches or greater. More specifically, in particularly preferred embodiment, the extrusion die was adjusted to 52 inches wide by 0.0005 inches in thickness. The adhesive composition may be coated onto the release sheet using techniques known in the art (such as discussed above) and as a continuous layer or printed into a desired pattern. A second release sheet may be applied to sandwich the adhesive layer. After application to the release sheet, the layered structure may be cut into sheets or wound into a roll. Preferably, it is continuously extruded and wound into a roll (e.g., a four thousand yard roll). In step 220, the extruder is operated to extrude the material onto a release sheet. The release sheet is a silicon coated release paper or other release materials as known in the art. In step 225, the extruded materials are the utilized for coating desired substrates applied to ballistic substrates when removal of the release sheet occurs.

[0054] Optionally, the release sheet may be eliminated by coating the adhesive composition directly onto a desired ballistic substrate to become a composite material (e.g., ply of composite material), thereby simplifying the manufacturing by elimination the release sheet. For example, the extruder may operated to directly coat onto a ballistic substrate (e.g., aramid material) to form a composite laminar structure, thereby minimizing the number of manufacturing steps and, thus simplifying the process. Multiple layers may be prepared by sequential steps as is known in the art.

[0055] In one embodiment step 225, includes producing a composite laminar structure via a laminator. A ballistic substrate is used for forming a composite laminar structure. For example, the release sheet and aramid woven or non- woven fabric is feed into the laminator, thereby heating the aramid and/or release sheet to the desired temperature such that the adhesive on the release sheet is melted onto the substrate. Of course, other methods as known in the art may also be utilized to produce the composite materials with the release sheet. [0056] The following are illustrative examples of the invention and are not intended to limit the same.

Example I:

[0057] A modulated differential scanning calorimetry (DSC) was conducted on a hot melt adhesive composition having the following formula:

Formula 1 - The hot melt adhesive was prepared by mixing the ingredients in an adhesive churn at an elevated temperature of about 325 ⁰F for about 2 hours, the ingredients are listed below:

1. Exxon AT 325- 10 parts at about 47 weight percent. "Escor" resin:

(ethylene-acrylic acid-methyl acrylate terpolymer). Melt index 25.

2- Exxon TC-221 or 220 - 6 parts at about 28 weight percent. "Optima" resin: EMA co-polymer ethylene methyl acrylate. Methyl acrylate-27%, approximate Melt index at 5.

3. Unitac from Union Camp or Arizona-Acid Rosin 7.5 parts at about 35 weight percent. Acid number is between about 128 to 145. Melt point ranging from about 78-85 ⁰C:.

4. Marcus Wax 3500 - 1.7 parts at about 8.4 weight percent oxidized high density polyethylene with an acid number of 24. Melt point 112°C.

5. Triple pressed Stearic Acid - 1.7 parts at about 8.4 weight percent. Melt + 60⁰C, Acid number of about 30 for initial flow at low temperature.

[0058] FIG. 3 illustrates the results of the modulated a differential scanning calorimetry (DSC) of a hot melt adhesive according to this example. Differential scanning calorimetry (DSC) is used to determine a wide range of physical properties of materials, including the glass-transition temperature Tg, the melting temperature Tm, and solid-solid transitions. In this technique, a sample and a reference material are subject to a controlled temperature program. When a phase transition such as melting occurs in the sample, an input of energy is required keep sample and reference at the same temperature. This difference in energy is recorded as a function of temperature to produce the DSC trace.

[0059] Modulated DSC provides the same qualitative and quantitative information about physical and chemical changes as conventional DSC, and it also provides unique thermochemical data that are unavailable from conventional DSC. The effects of baseline slope and curvature are reduced, increasing the sensitivity of the system. Overlapping events such as molecular relaxation and glass transitions can be separated. Heat capacity can be measured directly with modulated DSC in a minimum number of experiments.

(0060] Referring to FlG. 3, a modulated DSC of a sample having a size of about

10.68 mg and run on a TA instruments Q-100 modulated DSC. The method log illustrates the parameters of the test. More specifically, the experiment modulated at +/- 1.00⁰C every 60 seconds at a ramp of 2.00°C/min to 200⁰C. From the resultant graph it can be shown that the material has a broad melting point with a peak at about 62.7 ⁰C. The broad melting point is indicative of a multiple component mixture each having varying melting temperatures. Also, from the chart it is shown that the material has a glass transition temperature at about 16.2°C.

[0061] FIG. 4 illustrates a viscosity diagram of a hot melt adhesive according to an exemplary embodiment. Referring to FIG 4, the same hot melt adhesive composition of formula 1, above, was run on a Texas Instrument TA AR 500 to determine viscosity data. The raw phase is a set point line to ensure the data was run on the instrument within its internal parameters. As shown, the raw phase is below about 8O⁰C, thereby indicating the data is characterized as being accurate and acceptable within the tolerances of the equipment. The storage modulus is a measurement of energy stored during deformation and related to the solid-like or elastic portion of the elastomer. E' is used for stretching deformations; G' is used for twisting or torsional deformations. The loss modulus is a measurement of energy lost (usually lost as heat) during deformation and related to the liquid-like or viscous portion of the elastomer. E" is used for stretching deformations; G" is used for twisting or torsional deformations. Tan Delta (tan δ): is Indicative of the material's ability to dissipate energy, where tan δ = E"/E' = G'VG'. One of ordinary skill in the art would understand these parameters.

[0062] Referring to FIG. 4, the storage modulus (G') drops off at about 70-75⁰C at and about 50 X E7 Pa, also it ends at about 1000 Pa at 100⁰C. This shows that the material is initially a solid to about 70-75⁰C and melts as storage modulus decreases. The tan delta is the ratio of the loss modulus to the storage modulus. Referring to the tan delta, which appears to indicate the material goes through two melts. Overall the chart shows that the material starts off as being a solid and melts as the temperature increases.

Example 2: [0063] In this illustrative example, a woven cloth made of polyaramid fibers (Kevlar^®

29) having a denier of 3000 was cut into swatches 18 inch by 18 inch. Ten plies of cloth coated on one side were adhered together with an hot melt adhesive layer, 0.005 inches thick positioned between adjacent cloth plies to adhere the plies together as a one piece composite helmet shaped structure weighing 2.25 pounds. The hot melt adhesive composition had the same formula as formula 1 above.

[0064] Unexpected results were obtained when a 0.020 thousandths of an inch

Kevlar^® cloth was coated with 0.005 thousandths of an inch of the above thermoplastic adhesive and fashioned into a 12 ply thick laminate.

[0065] The 12 ply laminate was heated in a convection or microwave oven, while the laminate was positioned into a polyethylene bowl, to give a preliminary shape. It was dropped into a female mold and pressed into shape by a cold male mold lowered into the cavity and let to cool. The resultant laminate was up to (twice as strong as what is required) in a 5 shot test and averages 24% more energy absorbancy than currently Kevlar^® composites.

[0066] In one test the laminate was placed in a fixture. The distance from the muzzle of a gun having a 10 inch barrel to the helmet was 16' total distance.

The results are shown in Table 1.

Table 1:

Test

Conditions

Temperature

O F

Humidity

9%

Barometric

9.86

Clay Temp

OO F

CSay Block

Fixture

Sample Wet/ 0-30 Shot NlJ Shot Caliber Bullet Wt/Tyρe Velocity Penetration

Weight 1 deg. No. Location Ips IFS (mmm)

(LB) Dry Angle

2.7 } 1 44Mag Rem 240 GrJHP 1457 22

Dry 0 1

2 44Mag Rem 240 GrJHP 1456 24

0 2

3 44Mag Rem 240 GrJHP 1444 22

0 3

4 44Mag Rem 240 GrJHP 1441 22

0 4

5 44Mag Rem 240 GrJHP 1456 32

0 5

44 mm allowed

Note: Mag Rem is Magnum Remington; Gr JHP is grain jacketed hollow point

[0067] These specifications permit penetration of 44 mm under the test conditions used in this example. As shown in Table 1, the results obtained with the composite laminar structure of this invention was as low as 22 mm.

Example 3:

[0068] In this illustrative example, Kevlar^® fabric yarn of 3,000 denier was used.

Uncoated Kevlar^® fabric has an areal density of 12 oz/yd² (0.083 lb/ft²). The areal density of 20 plies of uncoated Kevlar^® fabric is 1.67 lb/ft³. The specific gravity of the adhesive composition from Example 2 is 0.98 (0.354 lb/in³). At a resin having the same formulation of formula 1 was coated to a thickness of 0.005 inches, the areal density of a single resin layer is 0.0255 lb/ft² and the areal density of 20 layers is 0.51 lb/ft². The total area! density of 20 plies of coated fabric the is 1.67 lb/ft² plus 0.51 lb/ft² equaling 2.18 lb/ft². The total resin content is 23.4% by weight of the fabric.

Projectile Testing

[0069] The U.S. Army historical database predicts a (0.30 Caliber FSP) V₅₀ of about

1,600 ft/sec for bonded Kevlar^® having an areal density of 2.18 lb/ft² (34.9 oz/yd²). The 20 ply panel tested had a V₅₀ of 1,786 ft/sec. This is an 11.6% increase in projectile velocity and 24.6% increase in projectile energy. The results are shown in Table 2.

[0070] The resin content used in the panel tested was somewhat higher, not lower, than traditional bonded armor laminates. It is hypothesized that the impact absorbing adhesive resin aids the Kevlar^® fabric to stop the projectile, In other words, the impact absorbing adhesive resin according to the invention may be termed a "ballistic" resin as opposed to a traditional "structural" resin which does not contribute to the ballistic performance of a fiber reinforced laminate.

Table 2:

Calculated V₅₀: 1786 ft/sec. Extreme Spread: 110 ft/sec.

Comments: (*) Impacts for V50 Calculation

Example 4:

[0071] A woven cloth made of polyaramid fibers (Kevlar 29) having a denier of about 3000 and a 17 by 17 weave cloth. About eighteen plies of cloth coated on one side were adhered together with an adhesive layer, 0.002 inches thick positioned between adjacent cloth plies to adhere the plies together as a one piece composite. An outer layer of hard thermoplastic surface, e.g., Lexan or similar thermoplastic surfaces, was added to the surface. It was heated in an oven to a temperature of about 250 ⁰F in a bag with a vacuum drawn for about 15 minutes at pressure below atmospheric, while the laminate was positioned into a polyethylene shield, to give a preliminary shape having a thickness of about .400 inches. The adhesive layer was formed from the same composition of formula 1 above.

[0072J A test was conducted according to the NIJ 0108.01 test procedure, which has a pass/fail standard. The minimum impact velocity is 1400 feet per second for both types of ammunition 9 mm parabellum and 0.44 magnum. As shown, from Table 3, there was no penetration of 44 Mag or 9 mm under the test conditions used in this example. These results indicate an highly resistance ballistic material.

Table 3:

Test Conditions Range 3

Temperature 7O F Muzzle to Sor 1 6 50 ft

Humidity 40 % Screen 1 - 2 5 73 ft

Si/e 36"x24 5" Screen 2 - Target 4 75 ft

Thickness 400' Midpoint to Target 7 50 ft

Test Specification N l J 0108 01 Target to Witness 5 ft

Threat Level iiiA Witness Plate 2024-T3 Alum

REMARKS

Sample Description Rigid polyaramid fiber

Shot 1 Perpendicular shot at the body of the shield (handle screw)

Shot 2 Perpendicular shot at the body of the shield

Shot 3 Perpendicular shot at the junction of the viewport and the body of the shield (viewport screw)

Shot 4 Perpendicular shot on viewport

Shot 5 30 degree shot at the junction of viewport and the body of the shield

|0073] Table 4 below shows results from MIL-STD-622F of the same composite laminar structure of this example 4. It establishes theoretical thresholds where 50% of the bullets completely penetrate the barrier and 50% partially penetrate the results are thus referred to as the V₅₀. The higher the V₅₀ the better the protection level of the barrier. Generally speaking , a barrier will have a V₅Q that is something like 150 fps faster than the minimum test velocity of the pass/fail test (called a VO, since none of the bullets can completely penetrate). The composite materials as described in Example 3 had a 1713 fps, which is 313 fps faster than the test velocity minimum, which is quite good. See Table 4 below for a complete listing of the results. Table 4:

Sample BALLIST IC THREAT Range 3

Projectile: 9 mm Muzzle to Scr. 1 : 6.58 ft.

Size: 36 Weight: 124 FMJ Screen 1 - 2: 5.73 ft. x24.5"

Weight 21.21 Ib. Powder: Power Pistol Screen 2 - Target: 4.09 ft.

Humidity: 40 % Barrel Length: 14 in. Target to Witness 0.5 ft.

No. of Plies: N/A Obliquity: 0 Midpoint to Target: 6.89 ft.

Temperature: 70 deg. F. Test Spec: Mil-Std-662F

Chronograph 1 Chronograph 2

AVERAGE Penetration

Shot TIME VELOCITY TIME VELOCITY Velocity SHOT Complete

No. Powder ms-5 fps ms-5 fps (fps) Loss Instrument I nd. Partial

I 9.0 346.1 1660 245.8 1662 1661 0 1661 N P

2 9.4 329.2 1740 234.4 1743 1741 0 1741 Y C

3 9.2 339.9 1685 242.1 S 687 1686 0 1686 Y P

4 9.3 337.2 1699 240.2 1701 1700 0 1770 Y C

5 9.2 342.1 1674 243.7 1678 1675 0 1675 Y P

6 9.3 335.7 1706 239.1 1708 1707 0 1707 Y P

7 9.5 323.9 1769 230.8 1770 1769 0 1769 Y C

(0074] These results indicate a highly resistant ballistic material.

[0075] FIGs. 5 and 6 illustrate composite substrates with ionomer and hot melt adhesive compositions according to further embodiments of the invention. In FIG. 5, a plurality of ballistic substrate layers 105, 1 10, 115, and 120 are provided along with a plurality of impact absorbing adhesive resin layers 515, as previously described. In addition, adhesively bonded ionomer top exterior layer 505 (e.g., DuPont Surlyn^® 8920 or 8940, ExxonMobil IOTEX™ 8000, and the like), preferably in the range of 0.002"-0.150", are provided and which improves stiffness and the ballistic characteristics of the composite substrate of FIG. 5 synergistically. When one or more additional impact absorbing adhesively bonded ionomer internal layers 525 (e.g., DuPont Surlyn^® 8920 or 8940, ExxonMobil IOTEX™ 8000, and the like) are employed, additional adhesive layers 520 are needed to bond them to the ballistic substrate layers 120. The one or more additional ionomer layers 525 also are preferably in the range of 0.002"-0.150", and are bonded to a polypropylene fabric bottom interior layer 510 with an additional adhesive layer 530, which can be other than the impact absorbing adhesive resin layers 515 (e.g., amorphous acid functional polypropylene hot melt adhesive, pressure sensitive olefin acid functional adhesive, and the like). Advantageously, the polypropylene fabric bottom interior layer 510 can be provided in order to keep a clean dry surface, for example, on the interior of a helmet. {0076] In FIG. 6, a plurality of ballistic substrate layers 105, 110, 115, and 120 are provided along with a plurality of impact absorbing adhesive resin layers 515, as previously described. In addition, an adhesively bonded inner ionomer layer 505 (e.g., DuPont Surlyn 8920 or 8940, ExxonMobil 1OTEX™ 8000, and the like), preferably in the range of 0.002"- 0.150", is provided and which improves the ballistic characteristics of the composite substrate of FIG. 6 synergistically. When one or more additional impact absorbing adhesively bonded ionomer internal layers 525 (e.g., DuPont Surlyn^® 8920 or 8940, ExxonMobil IOTEX™ 8000, and the like) are employed, additional adhesive layers 520 are needed to bond them to the ballistic substrate layers 120. The one or more additional ionomer layers 525 also are preferably in the range of 0.002"-0.150". The ballistic substrate layers 120 can be adhesively bonded to a polypropylene fabric bottom interior layer 510 with an additional adhesive layer 530, which can be other than the impact absorbing adhesive resin layers 515 (e.g., amorphous acid functional polypropylene hot melt adhesive, pressure sensitive olefin acid functional adhesive, and the like). Advantageously, the polypropylene fabric bottom interior layer 510 can be provided in order to keep a clean dry surface, for example, on the interior of a helmet.

[0077] In further exemplary embodiments, amorphous polypropylene adhesive layers including acid functional sites to bond to the ionomer surface can be provided when olefin fibers comprise the ballistic laminate. The ionomer sheet layers, optionally colored, placed on either end of the laminate, give optimum stiffness, for example, for the use in helmets and also give an inexpensive way to part a surface finish. Polypropylene copolymers and terpolymers are made by Eastman Chemical and HuIs division of De Gussa. The Vestoplast 750 type combined with Marcus wax MlOO @ 10/1 and acid rosin from Union Camp called Unitac 70 @ about 40% of the above, provides a satisfactory non polar adhesive for olefin ballistic strength fibers ensuring a hydrophobic laminar. Nonpolar organic polymers and their mixtures can be defined as having solubility parameters of about 15.8-18.8 or less. The cohesive energy calculation or dielectric constant of a nonpolar organic material is another way of describing low polarity and is defined in a book "Properties of Polymers" by D. W. Krevelen, Elsevier Science B.V., Amsterdam, 1994, incorporated by reference herein.

[0078] Amorphous polypropylene or polyethylene adhesives can be used to prevent water and moisture from being inadvertently introduced in the laminated structure. Olefϊnic adhesives, which are non-polar do not have any affinity for H₂O. When used to bond to the olefmic ballistic fibers Spectra or Dyneema, they create a structure which will not attract or harbor water and moisture. A completely non-polar armored laminar has unprecedented advantages. Without any moisture, the structure becomes more resistant to ballistic impact. If any moisture is present ,high velocity fragments or projectiles, upon impact, create steam, which works like a lubricant allowing a bullet to penetrate the armor more easily. Non-polar laminars also stay dry and light and if immersed in water, they dry much more quickly. When used as a matrix to envelope ballistic fibers, no moisture will collect in ambient conditions. Present day matrixes for polyethylene fibers are made from urethane, which has a polar isocyanate pendant that attracts ambient moisture and reduces its ballistic resistance. The amorphous olefin adhesive can have optionally, additional ingredients, as long as they have little or no polarity, such as rosins or waxes, and the like, to adjust the flow and surface tack. Acid functionality can also be desirable in some circumstances to bond to inorganic surfaces, such as ceramics, metals, or to organic materials with inorganic internal components and the like. The acid group should have low polarity, as imparted by most non esterified rosins.

[0079] Accordingly, FIG. 7 illustrates a composite substrate according to the further embodiments of the invention. In FIG. 7, olefin fiber or fabric layers 105, 110, 115, 120, and 720, as previously described, comprise the interior of the laminar with a ceramic top outer layer 705 and ionomer layers 505, 525, and 725 (e.g., DuPont Surlyn^® 8920 or 8940, ExxonMobil IOTEX™ 8000, and the like) near the top and bottom of the laminar for stiffness and ballistic synergy. Also provided are eutectic amorphous acid functional polypropylene copolymer adhesive mixture layers 710, and 715, which are non polar and have a SpG of under 0.96 and will bond ceramic tile, olefin fabrics, and ionomer sheets all together at temperatures between 200 ⁰F and 230 ⁰F. Advantageously, the composite substrate of FIG. 7 provides a light weight eutectic completely hydrophobic laminar armor structure unprecedented in the art.

[0080] The present invention includes the recognition of the importance of the eutectic properties of amorphous low polarity olefinic ballistic polypropylene copolymer adhesives, as used with attenuated polyethylene ballistic fibers, wherein polyethylene fibers start to lose their orientation or attenuation if heated much beyond 225 ⁰F so that they require adhesive coatings and matrix resins to activate well below that temperature and so not to lose fiber strength from heat imparted reduced orientation. Adhesives and matrix resins also should soften and stretch below 212 ⁰F so they allow the fibers and yarn to orient to the projectile's direction below the temperature at which any ambient moisture which may be in the armor laminar can turn to steam during manufacture or later in use and act as a lubricant or rupturing force in the laminar, delaminating it and causing voids . At least 25% of the ingredients in the adhesive should melt below 200 ⁰F to achieve this effect and preferably 33% or higher. In addition, the lower softening point of the adhesive or matrix increases the manufacturing productivity by decreasing the time needed to heat or cool the armor during its processing or molding or bonding phase.

[0081] The lower the manufacturing formation temperature requirement the better the elongation and orientation of the fibers to the direction of the projectile's impact. Some projectile energy may also be expanded in the phase transformation from solid to viscous fluid, helping to reduce penetration depth. In exemplary embodiments, the solubility parameter minimums are in a range of 15.8-18.8 or less and the dielectric constant minimums are 2.3 or less for a hot melt amorphous polypropylene copolymer adhesive. The M-100 Wax is a low molecular weight, high density, polyethylene from Marcus Chemical and the rosin Unitac 70 is from a tall oil source at Union Camp (Foral AX hydrogenated rosin from Hercules, Wilmington Delaware). Foral AX, for example, is an acid functional wood rosin, which has been hydrogenated to control viscosity and to keep it from darkening. Both have a Ring and ball melting point of about 70 ⁰C (i.e., Unitac 70) and can be made from tall oil derived rosin.

[0082] It will be apparent to those skilled in the art that various modifications and variation can be made in the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.

Claims

THE CLAIMED INVENTION IS:

1. A composite laminar structure, comprising: an aramid or olefin fiber layer; a eutectic impact absorbing adhesive resin or adhesive composition layer; and an ionomer layer, wherein the aramid or olefin fiber layer is adhesively bonded with the eutectic impact absorbing adhesive resin or adhesive composition layer to the ionomer layer.

2. A composite laminar structure, comprising: an olefin fiber layer; a eutectic amorphous acid functional polypropylene copolymer adhesive layer; and an ionomer layer, wherein the olefin fiber layer is adhesively bonded with the eutectic amorphous acid functional polypropylene copolymer adhesive layer to the ionomer layer.

3. The composite laminar structure of claim 2, wherein the olefin fiber layer has no polarity within a matrix thereof and has no affinity for moisture.

4. A method of making a composite laminar structure comprising the steps of: an aramid or olefin fiber layer; forming a eutectic impact absorbing adhesive resin or adhesive composition layer on an aramid or olefin fiber layer; and forming an ionomer layer on the eutectic impact absorbing adhesive resin or the adhesive composition layer.

5. The composite laminar structure of claim 1, wherein the composite laminar structure is in the form of body armor, shielding, helmet, vehicle, or aircraft.

6. The composite laminar structure of claim 2, wherein the composite laminar structure is in the form of body armor, shielding, helmet, vehicle, or aircraft.

7. The composite laminar structure of claim 3, wherein the composite laminar structure is in the form of body armor, shielding, helmet, vehicle, or aircraft.