Material for antiballistic protective clothing

Material for antiballistic protective clothing comprising in a single-layer or multi-layer package or laminate at least one layer of a flat structure containing an organic dilatancy agent This flat structure is particularly suited for a trauma package in an antiballistic package. The flat structure with a dilatancy agent results in a significant improvement in the antiballistic effect and, in particular, a reduction in the trauma effect. The material finds special application for bullet-proof and splinter-proof vests and correspondingly for helmets. Moreover, the material of the invention can be used in clothing protecting against impact.

FIELD OF THE INVENTION 
The invention relates to a material for protective clothing, in particular 
antiballistic protective clothing, in the form of single-layer or 
multi-layer packages or laminates. 
BACKGROUND 
Numerous materials and designs have been proposed for the protection of 
persons against injury from projectiles, especially that resulting from 
the impact of projectiles and splinters on the body at high velocity. 
Among the materials, textile flat structures, particularly woven fabrics 
made from aramid fibers, are frequently encountered. The designs relate 
particularly to so-called antiballistic packages, that is, packages of 
multiple superimposed thin flat structures, predominantly woven fabrics, 
that are glued, pressed, sewn, or quilted together. 
In the case of materials for protecting persons, it is important to provide 
lightweight products with maximum wearing comfort. However, a compromise 
must be made in this case between antiballistic effectiveness, i.e., the 
protective action for the person requiring protection, and wearing 
comfort. In this regard, it is known that the increase in the number of 
layers or the weight per unit area of the individual layers can improve 
the protective action in most cases. This leads, however, to heavier 
antiballistic protective clothing and in turn to reduced wearing comfort. 
The so-called trauma package enjoys special importance for protective 
clothing. A projectile impacting a piece of protective clothing worn on 
the body is slowed by the layers of the antiballistic package such that it 
cannot penetrate the body and cause injury to the wearer of the protective 
clothing. However, the impact of the projectile causes a certain shock 
effect and possibly a trauma as a result. The trauma package, which in the 
antiballistic package is adjacent to the body, is intended to alleviate 
this effect. 
Various embodiments for the design of this trauma package have been 
proposed. GB-A 2 234 156 provides for a layer of moldable plastic secured 
to a fabric made from antiballistically effective material. 
A trauma package introduced into a fabric jacket made from aliphatic 
polyamide fibers and comprising a layer of a fabric made from 
antiballistically effective fibers, a layer of a flexible, semi-rigid 
polycarbonate, and multiple layers of a foamed material with good 
compressibility is proposed in U.S. Pat. No. 4,774,724. 
Furthermore, rubberized layers of antiballistically effective fabrics, 
pressed together, are also used for trauma packages. 
In most cases, however, the embodiments proposed until now for reducing 
trauma upon projectile impact do not exhibit the desired effectiveness. 
Some of the proposed solutions to the problem considerably reduce the 
wearing comfort of protective clothing, since the special anti-trauma 
layers result in a not insignificant increase in not only the weight and 
thickness but above all the rigidity of protective clothing. 
For this reason, the objective has been made to develop materials for 
protective clothing with the same or reduced weight, greater flexibility, 
and improved anti-trauma effectiveness. 
It has now been discovered that this objective can be met in a particularly 
advantageous manner if in antiballistic clothing one or more layers of the 
antiballistic package, and particularly the trauma package, comprise flat 
structures containing an organic dilatancy agent. 
The use of dilatant materials in ballistics has previously been disclosed 
in U.S. Pat. No. 3,649,426. This patent proposes flat structures for 
protective clothing, for example, that are produced by compressing 
dilatant mixtures. Such mixtures are those of inorganic materials such as 
metal oxides or silicon dioxide powder with liquids having a dipole 
character. In this case, the problem arises that, through compression, the 
liquid is removed from the dilatant system to a great extent and the 
desired effect is partially lost. However, if a reduced compression that 
largely retains the liquid phase is performed, the dimensional stability 
of these articles is fully inadequate when worn as protective clothing. 
Moreover, use of the dilatant systems proposed in U.S. Pat. No. 3,649,426 
for protective clothing results in diminished wearing comfort due to the 
weight increase caused by the compressed panels. Furthermore, as will be 
shown in more detail in the comparative example, infra, only a slight 
antiballistic effect can be attained using the embodiment described in the 
cited patent. 
SUMMARY OF THE INVENTION 
The stated disadvantages can be circumvented if individual layers of the 
antiballistic package and, in particular, one or more layers of the trauma 
package comprise a flat structure that has been saturated or charged with 
organic dilatancy agents. 
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
The phenomenon of dilatancy has not yet been satisfactorily explained. It 
is generally understood to mean the stiffening or change in volume of a 
substance due to a sudden mechanical stress, particularly the action of 
shearing forces or the impression of a shear gradient, whereby time 
influences or effects cannot be measured. 
Under a sudden mechanical influence, such as the impact of a projectile, a 
volume change resulting from combined shear and compression stress occurs 
and leads to a sharp increase in transmittable shear forces. 
For purposes of the invention, substances imparting dilatancy are 
understood to be all substances that, as a result of a sudden mechanical 
influence, undergo a stiffening or volume change in the manner previously 
described. 
The best known examples of dilatant systems are mixtures of quartz sand and 
water. Water is frequently used to form the liquid phase, but other 
liquids with dipole character can be employed for this purpose. As the 
comparative example will show, such systems are poorly suited for 
protective clothing. 
There are also organic compounds that are known to have dilatant 
properties. Polymers suitable for dilatant systems are styrene and its 
derivatives. Particularly suitable are copolymers of styrene with acrylic 
acid or methylacrylic acid or their esters. In addition, other copolymers 
of styrene and of compounds of polyacrylic or polymethylacrylic acid are 
appropriate for this field of application. Other applicable products are 
polyvinyl chloride and polyvinylidene chloride, as well as the respective 
copolymers. 
The polymers listed here are well suited for manufacturing materials in 
accordance with the invention. However, those cited should be considered 
as examples only and not as restrictive. Within the scope of the 
invention, all organic compounds that, through saturation or charging, 
impart properties of dilatancy on a flat structure can be used for 
manufacturing materials in accordance with the invention. 
The dilatancy-imparting polymers are preferably applied in the form of 
dispersions to flat structures intended for processing into protective 
clothing. Such dispersions, available as commercial products, frequently 
contain, in addition to the polymer and water, additional products such as 
alkyl esters of phthalic acid. 
The flat structures envisioned for protective clothing and containing a 
dilatancy agent are preferably textile flat structures with good affinity 
for polymer dispersions. Nonwoven fabrics are especially well suited for 
this purpose. 
Spunbonded fabrics or nonwovens produced from spinnable fibers or short 
fibers are equally usable. 
There are no restrictions on fiber type for the manufacture of the nonwoven 
fabric. Nonwovens made from polyester or polyamide fibers are well suited, 
but nonwovens made from other synthetic fibers or from native or 
regenerated cellulose fibers can also be employed. Furthermore, aramid 
fibers, often referred to as aromatic polyamide fibers, and frequently 
used in antiballistic protective clothing, can also find application as 
fiber material for producing the nonwoven fabrics. Another fiber with good 
antiballistic effectiveness that can be used to manufacture such a 
nonwoven fabric is polyethylene fiber spun using a gel spinning process. 
In addition to nonwoven fabrics, which are preferably used as carriers for 
the dilatancy agent in manufacturing materials in accordance with the 
invention, other textile flat structures such as woven fabrics, knitted 
fabrics, thread composites, stitch-bonded textiles, and others can be used 
as carriers for the dilatancy agent. It is important that there be good 
affinity for the dispersion containing the dilatancy agent. Also suited as 
such carriers are non-textile flat structures such as foamed materials. 
The best results with respect to antiballistic effectiveness have been 
attained with nonwoven fabrics as carriers for the substance exhibiting 
dilatancy. Due also to the usually low initial weight, these are 
particularly suitable for protective clothing. 
The flat structure to receive the dilatancy-imparting dispersion is 
saturated with the dispersion and squeezed slightly. Since a large 
quantity of the dilatancy agent is required on the carrier material, high 
bath concentrations are necessary. For example, a steeping bath for 
finishing a carrier material is prepared using approximately equal parts 
of water and a commercial dispersion of the dilatancy agent. Depending on 
the desired effect, method of application, and solids content of the 
dispersion of the dilatancy agent, however, the ratio of water to 
dispersion of the dilatancy agent in the treatment bath can vary from 3:7 
to 7:3, for example. As are the percentages cited below, the values given 
here are examples only and are not to be considered restrictive. 
Especially suitable for applying the dilatancy agent on the carrier 
material are so-called padding processes, which can be conducted 
continuously such as on a padding machine. These processes are well known 
in textile finishing. A special variant is represented by padding 
processes in which the treatment bath is not located in a pad box, but 
rather in a nip formed by the squeezing rollers. Another application 
possibility is the use of slop-padding processes, which are likewise well 
known in the textile finishing art. 
In addition to application in a bath in conventional form, foam application 
is also possible. This method is also well known in the textile finishing 
art. 
Following application of the dilatancy agent to the carrier material, 
squeezing is conducted, for example, using a pair of rollers as are 
present on a padding machine. The degree of squeezing following wet 
treatment is adjusted, for example, such that the finished carrier 
material retains approximately 30-70% of the applied dispersion after 
squeezing. 
With a bath concentration of 50% dispersion, the weight increase of the 
treated carrier material following squeezing must therefore be 
approximately 60-140% with respect to the dry carrier material. 
In addition to those mentioned, however, there are other possible methods 
of applying the dilatancy agent to the carrier material. For example, it 
can be sprayed or poured on. In this case as well, the aforementioned 
concentrations can be employed. 
When using chemical fibers for manufacturing carrier materials, the 
dilatancy agent can even be applied during the fiber manufacturing 
process, together with a finishing agent, for example. 
The flat structures finished with a dilatancy agent can be applied in 
protective clothing in that wet or dry state. Use in the dry state is 
preferred. In this case, it is necessary to dry finish flat structures 
following wet treatment. This drying step should take place under gentle 
conditions, that is, at relatively low temperatures. The drying 
temperature depends on the type of polymer used. For example, the drying 
temperature in the case of polystyrene or its copolymers must not exceed 
80.degree. C. 
In addition to the preferred dry-state application for flat structures 
provided with a dilatancy agent, use in the wet state is also possible. In 
this case, the same concentrations for the dispersion containing the 
dilatancy agent are used as for the dry state. In a wet-state application, 
the flat structure finished with a dilatancy agent must be sealed in a 
dampproof jacket, made of sheet polyethylene, for example. In this form, 
the flat structure finished with a dilatancy agent is incorporated as a 
layer in the antiballistic package. 
The flat structures finished with a dilatancy agent can be used in various 
forms for protective clothing. A preferred application of these materials 
of the invention is in antiballistic protective clothing, especially 
preferred as a trauma layer in antiballistic protective clothing. Such 
antiballistic protective clothing is worn in the form of vests, for 
example, often referred to a bulletproof vests. The actual protective 
layer in these vests is formed by the so-called antiballistic package, 
which frequently comprises a large number of superimposed layers of aramid 
fiber fabrics that are sewn, quilted, glued, or pressed together. Packages 
with 28 such layers are common in bulletproof vests, for example. 
In accordance with prevailing terminology, layers that are quilted or sewn 
are normally referred to as "packages", while pressed or glued layers are 
often termed "laminates". The term "package", however, can also be 
considered a general term for all methods of strengthening. 
With such vests, for example, a flat structure finished with a dilatancy 
agent can be inserted into the antiballistic package, whereby this flat 
structure can serve as one of a total 28 layers of such a package, for 
example, or as an additional layer. The other layers comprise, for 
example, fabrics made from aromatic polyamide fibers with a weight per 
unit area of approximately 200 g/m.sup.2. The invention, however, is not 
limited to the use of only one layer of a flat structure containing a 
dilatancy agent. Depending on the desired effect, the antiballistic 
package can comprise multiple layers of these flat structures. The number 
of conventional fabric layers may be reducible through the use of multiple 
layers of flat structures containing a dilatancy agent. 
The flat structure containing a dilatancy agent is especially preferred for 
inclusion in the trauma package, that is, in the layers of the 
antiballistic package next to the body. When this flat structure is in the 
trauma layers of the antiballistic package, it functions as a form of 
shock absorber. The trauma effect occurring upon impact of a projectile 
can be reduced considerably by positioning a flat structure finished with 
a dilatancy agent close to the body. Good antiballistic effectiveness and 
reduction of the trauma effect are also observed, however, when the flat 
structure containing a dilatancy agent is positioned in an antiballistic 
package layer that is farther from the body. For example, an especially 
good antiballistic and anti-trauma effect can be achieved when at least 
one flat structure containing a dilatancy agent is used in the trauma 
package as well as in a layer farther from the body. 
The special trauma layers cited are particularly common for protective 
clothing in the form of bulletproof vests. In the same manner, however, a 
special trauma layer can be formed in a helmet using a flat structure 
containing a dilatancy agent. 
The statements made here concerning the positioning of flat structures 
containing a dilatancy agent apply likewise to the dry-state and wet-state 
applications of these flat structures. 
A particularly advantageous effect of a flat structure finished with a 
dilatancy agent when used in the trauma package is observed when a 
so-called support layer is used behind the trauma package, as viewed from 
the outside. In an especially preferred embodiment, this support layer is 
an aramid fiber fabric, as in the case of the antiballistic package. In 
the same manner, however, other fabrics made from high-strength fibers, 
particularly those with antiballistic effectiveness, can be used as 
support layers. In addition to aramid fiber fabrics, fabrics made from 
high-strength fibers spun using a gel spinning process are especially 
suitable in this case. Other fabrics made from other fibers such as 
carbon, polyester, or polyamide can be used as support layers, however. In 
addition to fabrics, other textile flat structures can find application as 
support layers. 
The flat structure used as a support layer, such as a fabric woven from 
aramid fibers, is normally not finished with a dilatancy agent. It is 
possible, however, to finish the flat structure of the support layer with 
such an agent. 
Due to the cited advantages, the material of the invention is especially 
suited for bulletproof and splinterproof vests, and for corresponding 
protective suits. In the same manner, however, it can also be used for 
antiballistically effective helmets. 
A further possible application of the material of the invention is for 
clothing to protect against impact, as is sometimes worn by athletes but 
also as occupational safety clothing. The phenomenon of dilatancy is 
exploited in a manner similar to that for antiballistic protective 
clothing. 
As has been shown, and as the embodiments will further confirm, the 
material of the invention provides a significant degree of protection in 
protective clothing. This is especially true for antiballistic protective 
clothing, in which the significantly increased protective action is not 
accompanied by any impairment of wearing comfort. The material of the 
invention has proven particularly suited as a shock absorber in the 
antiballistic package, that is, in reducing the trauma effect.

COMATIVE EXAMPLE 1 AND EXAMPLE 1 
In this example, the teachings of U.S. Pat. No. 3,649,426 are employed for 
the antiballistic protective clothing application of Comparative Example 
1. For this purpose, the mixture cited therein of 80% quartz sand, 16% 
glycerine, and 4% water is used. This mixture is introduced in the form of 
a 20 mm thick molded body into a jacket of sheet polyethylene and 
subjected to a bombardment test. This thickness represents an extreme case 
for antiballistic protective clothing. Normally, the thicknesses of 
antiballistic layers for bulletproof vests lie between 5 and 15 mm. 
The bombardment of the polyethylene-enclosed molded body of the cited 
mixture is undertaken with 9 mm Para ammunition (FMJ). Even at a 
projectile velocity of 200 m/sec, this package is completely penetrated. 
In the case of a standard antiballistic package comprising, for example, 
28 layers of an aramid fabric with approximately 200 g/m.sup.2 weight per 
unit area, total penetration occurs only in excess 460 m/sec. 
In Example 1, one layer of this 28-layer package is replaced by a polyester 
nonwoven finished with a dilatancy agent in accordance with the invention, 
such that there are 27 layers of aramid fabric and one layer of polyester 
nonwoven finished with a dilatancy agent. For the jacket of Example 1, 
total penetration does not occur until a velocity of 510 m/sec. 
These results show that the inorganic material proposed in the art for 
imparting dilatancy is unsuitable for antiballistic protective clothing. 
The molded body produced in accordance with U.S. Pat. No. 3,649,426 
exhibits completely unsatisfactory antiballistic properties at a thickness 
significantly exceeding that of the antiballistic package comprising 
unfinished aramid fabrics. Due to the considerable thickness of the molded 
body, its combination with aramid fabrics cannot be considered for 
antiballistic protective clothing. 
EXAMPLE 2 
For this example, the finishing of a nonwoven fabric with a dilatancy agent 
will be described. 
A nonwoven fabric manufactured by a carding process from polyester 
spinnable fibers with a titer of 3.3 dtex and a cut length of 60 mm and 
strengthened with a bonding agent is employed for finishing. The weight 
per unit area of the nonwoven is 102 g/m.sup.2. This nonwoven is finished 
on a laboratory padding machine. The preparation in the pad box of the 
padding machine contained 50% of Dilatal DS 2277 X from BASF of 
Ludwigshafen, Germany, a commercial dispersion of a copolymer of styrene 
and ethyl acrylate basis, with a diallylphthalate additive. The solids 
content of the dispersion is approximately 68%, and the bath preparation 
thus has a solids contents of approximately 34%. The degree of squeezing 
is set to 120%, that is, the total weight of the nonwoven after squeezing 
consists of 1 part nonwoven weight and 1.2 parts water and solids from the 
dispersion. Subsequently, drying is conducted on a laboratory dryer at 
80.degree. C. After drying, the weight per unit area is 143 g/m.sup.2. 
EXAMPLE 3 AND COMATIVE EXAMPLE 2 
The nonwoven finished in accordance with Example 2 is integrated into a 
bulletproof vest comprising 28 layers of an aramid fiber with a weight per 
unit area of 198 g/m.sup.2, whereby the nonwoven is employed for layers 29 
and 30, next to the body. Moreover, an additional layer of an unfinished 
aramid fabric with a weight per unit area of 198 g/m.sup.2 is incorporated 
as layer 31 behind the two nonwoven layer, as a so-called support layer. 
The structure from outside to inside therefore comprises: 28 aramid fabric 
layers, 2 layers of a nonwoven finished with a dilatancy agent, and 1 
aramid fabric layer as a support layer. 
In the bombardment test with 9 mm Para ammunition (FMJ), also used in the 
bombardment tests described below, and at a projectile velocity of 420 
m/sec, the penetration depth of the projectile into plastilina positioned 
behind the antiballistic package is 10 mm. In a further bombardment test 
of this bulletproof vest, the projectile velocity is increased to 510 
m/sec. In this case, the penetration depth into plastilina is 14 mm. 
Under the same bombardment conditions, a comparative bombardment test 
conducted with an antiballistic package comprising only 28 layers of the 
aforementioned aramid fabric results in a penetration depth of 38 mm into 
plastilina at a projectile velocity of 420 m/sec. At 510 m/sec, the 
projectile totally penetrates the antiballistic package. 
The determination of the penetration depth into a plastilina layer serves 
as a test of the trauma effect. For this purpose, the plastilina layer is 
positioned behind the antiballistic package. The penetration depth into 
plastilina is often also referred to as the trauma depth. Depending on the 
country, the trauma depths permitted by the authorities range from 20 to 
44 mm penetration into plastilina at a projectile velocity of, for 
example, 420 m/sec. 
The test described here not only demonstrates a significant decrease in the 
trauma effect by using the material of the invention; it also shows that 
the sometimes quite stringent requirements with respect to trauma depth 
can be achieved only by using the material of the invention in the trauma 
layer of an antiballistic package. 
COMATIVE EXAMPLE 3 AND EXAMPLES 4 AND 5 
Comparative Example 3 and Examples 4 and 5 show the positive effect of the 
support layer in an antiballistic package. In Comparative Example 3, a 
package of 28 layers of an aramid fabric with a weight per unit area of 
202 g/m.sup.2 is subjected to a bombardment test at a projectile velocity 
of 420 m/sec. The penetration depth into plastilina in this case is 37 mm. 
For the second bombardment test, i.e., Example 4, 6 layers of a lightweight 
polyester nonwoven finished with a dilatancy agent are positioned behind 
the package comprising 28 layers of an aramid fabric. The nonwoven has a 
weight per unit area of 118 g/m.sup.2 after finishing (unfinished weight 
per unit area 81 g/m.sup.2). From outside to inside, the package therefore 
is structured as follows: 28 layers of aramid fabric and 6 layers of 
polyester nonwoven. With this package, the penetration depth in the 
bombardment test at 420 m/sec projectile velocity is 13 mm. 
For the third bombardment test, i.e., Example 5, an additional layer of 
unfinished aramid fabric as a so-called support layer is positioned behind 
the nonwoven layers, such that the package now has the following structure 
from outside to inside: 28 layers of aramid fabric, 6 layers of a 
polyester nonwoven woven finished with a dilatancy agent, and 1 layer of 
aramid fabric as a support layer. In a bombardment test at 420 m/sec 
projectile velocity, the penetration depth is only 6 mm. 
While the invention has been described in detail and with reference to 
specific examples thereof, it will be apparent to one skilled in the art 
that various changes and modifications can be made therein without 
departing from the spirit and scope thereof.