Note: Descriptions are shown in the official language in which they were submitted.
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22189
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. ;
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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.
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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
108ZS85
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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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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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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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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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.
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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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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
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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
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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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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.
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