CA1082585A - Flexible laminated film material - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE A flexible armor structure is provided by laminating multiple units consisting of one or more plies of unidirection-ally oriented film or fibers which are positioned so that the lines of orientation of adjacent units are at angles to each other. The structure can consist of both bonded and nonbonded areas, and it can be completely nonbonded. The structure can also consist of either fibrillated or nonfibrillated film.

Description

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- -- 1082S~5 FLEXIBLE LAMINATED FILM MATERIAL
This invention relates to laminated film materials. It more parti-cularly relates to a laminated material comprised of oriented layers of film wherein the layers of oriented film are placed in the laminate such that the direction of orientation of the film differs from layer to layer. This invention further relates to laminates prepared from cross-lapped layers of oriented film wherein each laminate is comprised of both rigid and flexible portions. This invention still further relates to laminates prepared from cross-lapped layers or oriented film wherein there is provided a flexible laminate which is completely nonbonded.
At present certain types of protective clothing, such as flak vests, comprise a system of pockets in which are placed separate and dis-tinct pieces of rigid armor material. This system of pocketed carrier material and individual pieces of armor is necessary in order to provide the wearer with requisite flexibility essential to normal body movements.
There is, therefore, a need for an armor material which permits the con-struction of protective clothing, for example, a flak vest, from a single piece of material which could be fitted completely over a given area while still permitting flexible movements of the wearer. ;

It is thus an object of this invention to provide a novel, laminated material which is highly flexible and which is suitable for use in the manufacture of protective clothing.
The various aspects and advantages of this invention will be-come apparent to one skilled in the art from a consideration of thefollowing specification, figures and claims.
In accordance with this invention there is provided a novel flexible laminated article of manufacture. The fact that the mater- -ial is flexible renders it more useful as a body armor in that it is more readily fitted to body contours without need for extensive car-rier material. Also, the flexibllity feature permits the manufacture of protective clothing from fewer if not a single piece of material which eliminates the possibility of gaps in the protective material.
In one embodiment of this invention the article contains therein areas or portions of plies which are bonded one to another through-out the entire thickness of the article, and areas or portions of plies which are not bonded together at all. This combination of bond-ed areas and nonbonded areas in the same laminated article produces a material which is rigid in part and flexible in part. In this embodiment the article bends, that is, it is flexible, in lines parallel to the bonded portions of the structure with the lines of flexing lying wholly within the nonbonded portions of the structure.
Thus, by forming bonded and nonbonded patterns within the laminate structure of this invention, one can design into the structure spec-ific flexible portions to accommodate specific body movement.
In another embodiment of this invention the plies of the novellaminated article of manufacture are completely nonbonded and no portion or area of the laminate is bonded. Thus in this embodiment the entire article is flexible in every portion thereof and it con-tains no rigid areas.

-' ~.os%sss This invention thus provides a flexible, light-weight, armor-structure- forming material having high impact resistance whic~. is comprised of a plurality of units of unidirectionally orien-ted film or fibers. The units in the structure are stacked one an top of the other such that the lines of orientation of adjacent units are at angles to each other. Each unit consists of at least one ply or single sheet of unidirectionally oriented film or fibers, wherein all plies in a single unit are positioned such that the lines of orientation of the pl;~es are parallel. When a desired number of units are stacked, the resulting stack can be either bonded to-gether in certain desired areas by the application of heat and pres-sure to produce a single structure having therein both rigid and flexible areas, or the stack can remain completely nonbonded to pro-vide a single structure which is flexible in all areas and directions. -If it is elected to permit the stacked units to remain completely non-bonded, then it is necessary to maintain the units of the resulting nonbonded structure in stacked relationship by any suitable means, such as by stitching, wrapping in a confining enclosure, encasing in a sleeve material, and the like.
In still another embodiment of this invention the individual plies of the article can be fibrillated to thus form split or open æheets. The fibrillated sheets are then placed in the article as abo-ve described with respect to the placement of plies and units in the article and the article can then remain nonbonded or it can be bon-ded in desired areas. The article thus consisting of the $ibrillated plies not only forms a structure which is flexible either in its entirety or having both rigid and flexible portions, but also forms a struc-ure which is porous, thus offering a breathable material.
The plies can be fibrillated by any means known in the art for the fibrillation of unidirectionally oriented film such as the methods of Rasmussen disclosed in U. S. 3,345,242, or Brown disclosed in U. S. 3,511,901.

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The materials utilized for formation of each unit are capable of being formed into filaments or films which can be drawn (oriented) to a high percentage of elongation. While any means for orienting the material can be used, the material~should be highly oriented, utilizing a draw ratio in the range of 6:1 to 20:1, preferably in the range of 9:1 to 14:1. The preferred materials are solid, high molecular weight synthetic olefin polymer products or mixtures there-of formed by he polymerization of at least one monolefin having from

2 to 8 carbon atoms therein. Polyethylene, polypropylene, poly(l-butene), ethylene-l-butene copolymers, ethylene-propylene copolymers, ethylene-l-hexane copolymers and the like, as well as blends or mix-tures thereof are polyolefins which can be used as materials in the structure.
In a preferred embodiment the specific polymeric material com-lS prises a blend of polypropylene and polyethylene wherein the poly-propylene is present to the extent of 75 to 99 percent by weight and the polyethylene is pres~nt to the extent of 25 to 1.0 percent by weight of the blend.
In another preferred embodiment the specific material consists 2~ of polypropylene which is present to the extent of 100~ by weight of the material.
Each unit in the structure contains from 1 to 100 plies or more, preferably from 2 to 40 plies, wherein the direction of orientation of each ply in a sin~le unit is the same, and wherein each ply has a each ply has a thickness of 0.5 to 25 mils. In the formation of the structure, adjacent units are placed in any stscked relationship so long as their direction of orientation is not parallel. It is pre-ferred that the direction of orientation of adjacent units differ by 90 degrees, but lesser angular differences can be employed.

Bonding of the units consisting of one or more plies to form the desired structure is carried out by subjecting the composite of posit-ioned units to compression at elevated temperatures. Due to the unique nature of the ply-forming material no additional adhesive or bonding agents are required in the formation of the desired laminate.
The material or composite of units, after being positioned in the above-described manner, is placed into a press containing appropriately shaped plates, also as herein des-cribed, and subjected to an elevated temperature below the melting point of the polymer composition at atmospheric pressure, and to a pressure sufficient to achieve the desired lamination. Ordinarily a press plate temperature in the range of 50 to 200C. is emPloyed.
Pressure at which the press is operated is in the range of 50 to 100, 000 psi and preferably 1000 to 50,000 psi. Plate pressures and plate outside these ranges can be utilized in achieving bonding or lamination of the ply units, but the above conditions for bonding are most suitable when utilizing conventional pressing apparatus.
The flexibility of the material is produced by not bonding the entire structure together. Thus, the bonding technique utilized owing to specific irregularities in the configuration of the press plates or platens, produces in the structure of one em-bodiment of the present invention both bonded and nonbonded areas.
FIGURES 1, 2, 3, and 4 illustrate two basic patterned structureswhich demonstrate the flexibility feature of the previously mentioned embodiment of this invention having both bonded and nonbonded areas.
Referring specifically to FIGURE 1, there is shown a plan view of one patterned structure of the laminated structure of this invention, having depressed areas therein, such as 1 and 6, which are completely surrounded by raised areas, such as 2, 3, 4, and 5.
The particular shapes of the depressed and raised areas are of no known significance, that is, they could be substantially square, as~shown, or rectangular, round, or any other convenient shape.
Likewise, the spacing between depressed areas, such as between 1 and 6, is also of no known significance, however, it is preferred that the spacing be such that upon bending at a 90 angle adjacent raised areas will not touch.

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~:- 1082585 The significance of the pattern illustrated in FIGURE 1 resides in tho fact that the raised areas are interconnecting. The material is flexible within raised areas, which are nonbonded areas, and bends along and around any straight line axis which passes through contin-uous nonbonded areas. Since the nonbonded areas shown in FIGURE 1are interconnecting this pattern permits flexibility areound inter-secting axes. Exampls of such intersecting axes of flexibility are axis a-a and axis b-b which pass through raised areas 2 and 5 respectively of FIGVRE 1. The material is not generally flexible within depressed areas, which are bonded areas, and does'not bend along and around any straight line axis which passes through a de-pressed area. An example of such an axis of nonflexiblity is axis c-c which passes through the depressed areas indicated in FIGURE 1.
The depressed areas of the laminate, such as 1 and 6 of FIGURE
l,'are areas which are firmly bonded by the application of heat and pressure. The various plies and units within the depressed areas ha,ve had sufficient heat and pressure applied for a sufficient length of time to achieve a securely bonded laminated material.
, The condition of the laminate within the depressed-bonded areas is generally rigid rather than flexible so that bending ordinarily does not occur around an axis which passes,through a bonded area.
The raised areas of the laminate, such as 2,3,4, and 5 of FIGURE 1, are areas which are either not bonded at all or are not firmly bonded. These areas, although perhaps subjected to heat relatively less pressure than the adjacent bonded areas. Conse-quently , these raised areas are not bonded as firmly, if bonded at all, as the adjacent depressed aréas. As a result the raised areas are not rigid but, instead, are, flexible, and the laminate bends along and around straight axes lying within the flexible-nonbonded areas.

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'- 108Z~85 Referring now to FIGURE 2, which is a sectional view of the structure of FIGURE 1, it is seen that both sides of this laminate structure have the same configuration. Thus the depressed areas 1 and 6 and raised areas 2, 3, and 4 of FIGURE 2 correspond to their respective indicated locations in FIGURE 1.
It is also wlthin the scope of this invention to produce a structure having an irregular surface configuration, such as the pattern illustrated in FIGURE 1, on one side and a flat planar confi- -guration on the reverse side. Such a structure would have otherwise all the flexibility features described with respect to Figure 1.
An apparatus used to prepare a laminate material such as the structure shown in FIGURES 1 and 2 can be a standard press, such as a hydraulic press, equipped with pressure plates on both jaws of the press, with each plate having raised sections which protrude from the face of the plate. These plates are similar to the opposing plates of a waffle iron. The protruding sections on each plate are positioned to meet headon with a raised section on the opposite plate rather than dovetail or key. The positioning of .
the protruding sections on the plates can be conveniently altered to accommodate the particular pattern of bonded and nonbonded areas desired on the finished product. Opposing raised sections are positioned to provide a bonded area, and a pace, i.e., no such raised sections, is positioned where a nonbonded area is desired.
Maximum pressures are thus developed between opposing raised sections and relatively lower pressures are developed between opposing spaces. The extent of the pressure differential developed between the areas of material between raised sections and the areas of material between spaces is a function of raised section height and spacing.
Referring to FIGURE 3, there is shown a plan view of a second type of the laminated structure of this invention, which consists of continuous rows of depressed areas, such as 7, alternating with con-tinuous rows of raised areas, such as 8, with alternating rows ofraised and depressed areas thus producing a ribbing configuration.
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~ ~o8zs8s The resulting structure is similarly rigid and flexible in the depressed and raised areas as described in FIGURE 1. However, since the raised areas in FIGURE 3 are not interconnecting tas they are in FIGURE 1) and the depressed areas, such as 7, are instead uninter-rupted, the patterned structure illustrated in FIGURE 3 does not per-mit bending about sets of intersecting axes as does the structure illustrated in FIGURE 1.
The structure illustrated in FIGURE 3 is flexible about axes through raised areas, such as axis d-d through raised area 8, and is not generally flexible about axes through depressed areas, such as axis e-e.
Referring now to FIGURE 4, which is a sectional view of the structure shown in FIGURE 3, one side of this embodiment is ribbed and the reverse side has a flat planar configuration. Raised area 8 and depressed area 7 correspond to their respective indicated locations on FIGURE 3.
It is also within the scope of this invention to produce a structure having a ribbed configuration, such as the pattern illus-trated in FIGURE 3, on both sides. Such an embodiment would have all the flexibility features described with respect to FIGURE 3.
An apparatus and process as described to produce the bonded and nonbonded areas of FIGURES 1 and 2 is also useful as the process and apparatus for the formation of the laminate structure shown in FIGURES 3 and 4. The difference between the apparatus, however, is indicated by the differences between the two embodiments. Thus, one plate of the press is flat and the other plate contains rows of rais-ed bars in order to produce the structure shown in FIGURES 3 and 4.
The embodiment of this invention having both rigid and flexible portions is not intended to be limited to the patterned structures of FIGURES 1-4. These structures are provided to illustrate the flexiblity feature of the laminate, and to indicate that the material i8 flexible in and along nonbonded areas but is not generally flexible along or throu~h bonded areas. Appropriate application of the flexibility feature can provide different patterns of bonding and nonbonding which will satisfy a given flexibility problem.

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~08ZS85 As previously mentioned, in another embodiment of this invention the novel flexible laminate is completely nonbonded, that is, it contains no rigid portions. Since the article of this invention is made w;th highly unidirectionally oriented material the various plies of the nonbonded article are subject to excessive fibrillation. In those instances where nonfibrillated material is utilized to produce the article and excessive fibrillation of the plies is not desired, the material can be appropriately treated before it is used to make the article. For example, if a uniaxially oriented polymeric film is heated in localized areas to the melting point of the polymer, the polymer chains in such areas return to the random distribution of the unoriented film. This heating is best accomplished by a heated bar or heated embossed rolls placed against the film -surface at desired intervals and at an angle with respect to the direction of orientation. Ordinarily, the heated localized areas are at an angle of from 20 to 90 degrees with respect to the direction of orientation. A suitable embossing roll or heated bar that can be employéd for impressing localized heated areas onto the film are illustrated in U.S. Patent 3,131,425. Generally, it is -preferred to use a pair of embossing rolls having mated surfaces.
The important aspect of the treatment is to subject the oriented polymeric film to heating in localized areas to the melting point of the polymer so that the polymer chains in such areas return to the random distribution of the unoriented film and that upon subsequent fibrillation, the fibers are interrupted or stop at the fused lines.
Thus, by utilizing the above treatment, any fibrillation of the material in the article is stopped at the fused lines.

-' 1082585 The distance between fused portions is purely a matter of choice by the potential apparel manufacturer, but it is felt that the distance be random rather than regular to avoid the possibility of accumulations of a number of deoriented fused ply portions in or near a given cross section of the flexible article.
In addition to the use of the flexible article of my invention in protective clothing, such as in flak vests, it is also useful in other armor applications. The completely nonbonded article has particular value when used in the following applications: An armor plate having a spall shield is made by attaching to or holding in place on any armor-providing material a thickness of the flexible laminate. The flexible laminate can be held in place by nylon or other type cloth wrapped around the edges of the joined materials. Any armor-providing material such as ceramic plate or metal plate can be used to support the flexible material of this invention to which the material is attached, glued, or otherwise held or fastened. Using the flexi-ble laminate in this fashion also permits its attachment to a curved surface as well as to a plane surface.
In another application, the space in a rigid or flexible hollow shell structure is filled with the nonbonded flexible laminate of this inven-tion to thus form a sandwich structure useful to resist the impact of shell fragments and projectiles. Specific applications employing this principle include: an aircraft seat comprising a shell having therein a thickness of the flexible nonbonded laminate; placing the material in hollow spaces within the skin of an aircraft fuselage and placing it in and around critical but unprotected areas such as transmissions, engine covers and the like; and a crash helmet comprising a shell having therein a thickness of the flexible nonbonded laminate. The shell structure utilized can be any hollow shell structure such as one made by molding a two-piece structure (helmet, shoes, seat and the like) of plastic, such as a thermoplastic transparent sheet of acrylic synthetic resin, and the like. The material can be placed between the two pieces of the hollow structure and then they are fastened to thus trap the flexible material in the structure.

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108Z58~i The following examples further illustrate the laminated structure of this invention.
EXAMPLE I
A nonbonded composite, composed of oriented film tube of a blend of 95 percent polypropylene and 5 percent polyethylene which had been flattened and drawn at a ratio of 10 to 1 so that the wall thickness of the film was approximately 2 mils, was prepared by alternately crosslapping at 90 degrees the double sheets formed by the flattened tube, using 300 single sheets or 150 double sheets (150 units with two ply per unit). The resulting nonbonded composite of the plurality of sheets was approximat~ly 7 inches square. The composite was not subjected to either heat or pressure. Hence, it was not bonded at all. The nonbonded structure, which was 1/4 inch thick, was then placed on a soft wood backing with a 4-inch-square target area showing.

The structure was thereafter fired on from a distance of 6 feet by a 38-caliber police special pistol containing a 158-grain lead slug. The slug did penetrate the structure but it did not pass completely through it. The depth of penetration was approximately 1/32 inch, or approximately 12 percent of the total thickness of the nonbonded structure.
This example illustrates the bullet-stopping capability of non-bonded oriented, polyolefin film which has been positioned to form an armor structure.
EXAMPLE _II

A composite containing there~n both flexible (nonbondéd) and rigid (bonded) areas, and bieng composed or oriented film tube of polypropylene which had been flattened and drawn at a ratio of 10 to 1 to a final thickness of about 2 mils, was prepared by alternate-ly crosslapping at 90 degrees the double sheets formed by the flat~
tened tube using 300 single sheets of 150 double sheets (lS0 units with two sheets per unit). The resulting nonbonded composite .of the plurality of sheets was approximately 8 inches wide by 12 inches long.
The composite was placed in a heated hydraulic press, one 108z5~5 platen of which had been modified by the fastening thereon of 1/8-inch-thick by 3/4-inch-wide by 8-inch-long steel bars. The bars were placed in parallel and were -lla-- . , . . , ;
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spaced at l-inch intervals. The hydraulic press was then activated and the portions of the composite immediately under the raised steel bars were subjected to a pressure of 8000 psi at a temperature of 3 n 0 F. for a period of 1 hour. The portions of the composite between the raised steel bars were subjected to very little, if any, pressure and only slight, if any, surface bonding was effected in these portions. Thc thus treated composite was removed from the press; its configuration was similar to that illustrated in FIGURES 3 and 4 herein and it was found to consist of alternating strips of bonded and nonbonded material; the bonded portions were approximately l/8-inch thick and the nonbonded portions were approximately l/4-inch thick, The treated composite was found to be flexible within the nonbonded material in the direction parallel to the position of the raised bars on the platen.
EXAMPLE III
A 3-inch-wide by 8-inch-long sample was cut from the composite structure prepared in Example II. This sample consisted of alternating parallel bonded and nonbonded strips with the strips being parallel to the 3-inch dimension of the sample.
The flat side of the sample was placed against a wood backing (an 8-inch by 10-inch railroad tie) and the ribbed side was twice fired on from a distance of 6 feet by a 38-caliber police special pistol which was loaded with 158-grain lead slugs. One shot was fired into a bonded portion with the slug striking about

3/4 inch from the 8-inch edge of the sample, and the second shot was fired into a nonbonded portion with that slug striking about 2 inches from the first and about 1-lt8 inches from the 8-inch edge of the sample.
Neither slug penetrated the sample and both were instead deflected. However~ each slug did produce some delamination of the sample material.
The above examples clearly demonstrate the utility of this invention in providing a flexible material for personal protection.
Example I illustrates the bullet-stopping capability of the complete-ly nonbonded material. Example II

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~08Z585 is an illustration of the flexiblity of the laminate structure containing therein specific areas of flexiblity which were selected and formed as desired by appropriate design of the platens of the press. Example III illustrates the bullet-stopping capability of the flexible laminate structure of this invention and clearly demonstrates the ballistic efficiency of both the bonded and nonbonded portions. Example III also illustrates the retention of the bullet-stopping capability of the laminate structure after receiving one shot in that it also stopped a second slug which impacted only a short distance from the point of impact of the first.
Reasonable variations and modi~ications of this invention can be made or followed, in view of the~foregoing disclosure, without departing from the spirit or scope thereof.

Claims (15)

I CLAIM:

1. An armor structure comprising a layered article having therein nonbonded and bonded portions, said nonbonded and bonded portions being positioned as desired in separate and distinct portions of said armor structure to thus produce a laminate having therein both flexible and nonflexible areas.

2. The laminated armor structure according to claim 1 wherein said layered article is comprised of a plurality of units containing plies of unidirectionally oriented olefin polymer material, said plies being arranged in said units such that the direction of orientation of adjacent plies in each unit is the same, and said units being arranged in said article such that the direction of orientation of adjacent units is different.

3. The laminated armor structure of claim 2 wherein said olefin polymer material is formed by the polymerization of at least one monolefin having from 2 to 8 carbon atoms. therein, said material being capable of being formed into filaments or films which an be oriented utilizing a draw ratio in the range of 6:1 to 20:1.

4. The laminated armor structure of claim 3 wherein said olefin polymer materials is formed from a polymer blend which contains from 1 to 25 percent by weight of a solid polymer of ethylene and from 99 to 75 percent by weight of a solid polymer of propylene.

5. The laminated armor structure of claim 3 wherein each of said units contains from 1 to 100 plies of said unidirectionally oriented olefin polymer material, wherein each of said plies has a thickness of 0.5 to 25 mils.

6. The laminated armor structure of claim 5 wherein said nonbonded and said bonded portions are positioned therein to form alternating bonded and nonbonded strips across the surface of said article to thus form a product having at least unidirectional flexi-bility along and within said nonbonded strips.

7. The laminated armor structure of claim 5 wherein said nonbonded and said bonded portions are positioned therein to form bonded portions surrounded by nonbonded portions to thus form a product having at least bidirectional flexibility along and in said nonbonded portions.

8. The laminated armor structure of claim 5 wherein said nonbonded and said bonded portions are postiioned therein to form a combination of alternating bonded and nonbonded strips on the surface of said article and bonded portions surrounded by non-bonded portions to thus form a product having at least unidirectional flexibiltiy in at least one area of said armor structure and at least bidirectional flexiblity in at least one different area of said armor structure.

9. A flexible armor structure consisting of a completely nonbonded layered article, said layered article being comprised of a plurality of units containing plies of unidirectionally orient-ed olefin polymer material, said plies being arranged in said units such that the direction of orientation of adjacent plies in each unit is the same, and said units being arranged in said article such that the direction of orientation of adjacent units is different.

10. The flexible armor structure of claim 9 wherein said olefin polymer material is formed by the polymerization of at least one monolefin having from 2 to 8 carbon atoms therein, said material being capable of being formed into filaments or films which can be oriented utilizing a draw ratio in the range of 6:1 to 20:1.

11. The flexible armor structure of claim 10 wherein said ole-fin polymer material is formed from a polymer blend which contains from 1 to 25 percent by weight of a solid polymer of ethylene and from 99 to 75 percent by weight of a solid polymer of propylene.

12. The flexible armor structure of claim 10 wherein said olefin polymer material is polypropylene.

13. The flexible armor structure of claim 10 wherein said olefin polymer material is fibrillated film.

14. The flexible armor structure of claim 10 wherein said film is deoriented in randomly located fused lines prior to the production of said armor structure.

15. A hollow shell structure containing therein the flexible armor structure of claim 10.