IL127528A - Anti-fragmentation material and method of producing same - Google Patents

Abstract

An improved anti-fragmentation material (10) comprising: at least one layer of HPPE (High-performance polyethylene) material (12) sandwiched between fire resistant and anti-fragmentation layers (14).

Description

ANTI-FRAGMENTATION MATERIAL AND METHOD OF PRODUCING SAME FIELD OF THE INVENTION The present invention relates to protective materials and more particularly to anti fragmentation materials.

BACKGROUND OF THE INVENTION Anti-fragmentation and bulletproof vests, or inserts incorporated into existing vests, are commonly used in military and police work. Prior art known to the applicant discloses the following kinds of protective devices: upgrades and additions incorporated into an existing vest, vests which protect exclusively against fragment threats, and vests which are designed to protect against both ballistic and fragmentation threats.

Present anti-fragmentation materials are made of aramid or HPPE r (High-performance polyethylene) materials. However, aramid material is heavy. For protection against fragment threat, for example, of 17 grain fragment having a velocity of 500 m/sec, the typical weight of aramid needed is about 3.3 Kg per square meter. An anti-fragmentation vest made for such use will be very heavy and cumbersome. Another drawback of this material is its sensitivity to water and chemicals. Aramid must be treated with fluorocarbons in order to prevent the inevitable 40-50% decrease in its performance due to water absorbency. Not only is such treatment expensive, but even after this treatment, the measured decrease in the aramid' s performance when wet is about 10%.

HPPE cloth is also used in manufacturing protective materials but, although HPPE cloth is not sensitive to water or chemicals as is aramid, it is highly flammable and no fire retardant compound can be added to it without drastically reducing its anti-ballistic characteristics. Another material that has excellent anti-fragmentation properties is HPPE felt.

However, due to its physical and chemical structure, HPPE felt is a very water absorbent material. It has been found that the ballistic ability of a wet HPPE felt decreases by 40% to 60% due to the water absorbed in it. Thus, from this material alone one can not produce an effective anti fragmentation vest.

In view of the disadvantages of these materials, there is a need for a lightweight protective material that can be safely used against fragmentation threat.

The present invention aims at providing a novel, lightweight anti fragmentation material that overcomes the above drawbacks of the prior art.

SUMMARY OF THE INVENTION The invention provides an anti fragmentation material comprising at least one layer of HPPE material sandwiched between layers of a fire resistant material. For the purpose of the present invention, the term "layer" includes at least one sheet of material.

In a preferred embodiment of the invention, the HPPE material is HPPE felt. In a second embodiment, the anti fragmentation material also includes sealing means to provide water resistance to the fire resistant structure.

Furthermore, the present invention provides the following method of manufacturing the anti fragmentation material. First and second layers of unidirectional fire resistant material are cut. Then a selected amount of HPPE material is packed between the first and second layers of the fire resistant material. Preferably, the fire resistant material is enclosed within sealing means to form a water-resistant shell. In another embodiment of the invention the HPPE material is enclosed within a water-resistant shell and then packed between the first and second layers of the fire resistant material.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be further understood from the following detailed description taken in conjunction with the drawings in which: Fig. 1 is a schematic cross sectional view of an anti-fragmentation material in accordance with one embodiment of the present invention.

Fig. 2 is a schematic cross sectional view of a second embodiment of the anti-fragmentation material of the present invention.

Fig. 3 is a front view of an anti-fragmentation armor made of the anti-fragmentation material of the present invention.

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an anti fragmentation material effective in protection against fragments of shells, grenades, bomblets etc. The anti fragmentation material of the present invention can be formed in a variety of configurations, such as blankets, coats, vests, pants or any other desired form designed for anti fragmentation protection.

Referring to Fig. 1, there is shown a schematic cross sectional view of one embodiment of an anti-fragmentation material 10 of the present invention. The anti-fragmentation material 10 includes non- woven HPPE material 12, preferably HPPE felt, sandwiched between at least two layers of fire resistant material 14, preferably unidirectional material of 0/90 structure. Anti fragmentation material 10 further includes sealing means to impart water resistance to the fire resistant material. According to one embodiment the fire resistant material is treated in order to obtain a water resistant coating or outer shell. The treatment is performed by impregnation and curing as will be described hereinafter, and by sealing closure means 16, such as a tape, which is secured to the edges of the impregnated layers. Each layer of the fire resistant material can be made of several layers, which can be made from one or more than one material. Furthermore, each layer can be formed in a variety of textures or in different thicknesses, all in accordance with the needs of the user. The fire resistant material 14 is preferably made of fibers or woven fabrics.

Preferred fire resistant materials are aramids, such as Kevlar® (Du-Pont) of 190 gr/m2 or TM2® (Akzo) of 220 gr/m2. However, it will be appreciated by those skilled in the art that these preferred materials are non-limiting examples only, and that one can use any other fire resistant material, such as Nomex or asbestos. Furthermore, it will be appreciated that the fire resistant material can consist of more than one layer, according to the needs of the user.

The amount of HPPE material is determined according to the fragmentation threat against which the vest is designed to protect. In a preferred embodiment of the present invention, the weight density of the HPPE layers is above 600 gr/m2 for protecting against 17 grain fragment having a velocity of 300 m/sec. In another embodiment of the invention, the weight density of the HPPE layers is above 1200 gr/m2 for protecting against 17 grain fragment having a velocity of 450 m/sec. In yet another embodiment of the invention, the weight density of the HPPE layers is above 1800 gr/m for protecting against 17 grain fragment having a velocity of 500 m/sec. It will be appreciated by those skilled in the art that the above are non-limiting examples only, and that for other threats, such as for 25 grain fragments, one can use any other effective amounts of HPPE.

In another embodiment of the invention 10', shown in Fig 2, the fire resistant material 14 consists of a first layer 14a and a second layer 14b.

Fire resistant material 14 is enclosed within sealing means 18, here, a water-resistant outer cover. Sealing means 18 is preferably made of a water-resistant fabric, such as Nylon 6 or 66, that was impregnated with polyurethane. The water-resistant cover is sealed around the fire resistant material by means of a water-resistant sealing closure 16', as known in the art.

A preferred method of preparation of an anti-fragmentation material according to the present invention is as follows.

First and second layers of fire resistant material 14, preferably unidirectional, are cut into the desired form, then impregnated with fire retardant compound, such as polyethylene, and cured, for example at 180°c and 50 PSI. The cured layers are water resistant. A selected amount of HPPE 12 is packed, preferably in layers, between the first and second fire resistant layers. The edges of the fire resistant material 14 are then sealed, as by heat. The resulting anti fragmentation material is now ready for further textile processing, such as sewing, after which an anti-fragmentation armor 20, for example, as shown in Fig. 3, is manufactured. If desired, the resulting anti fragmentation material can be covered with a water resistant material or with some other fabric.

Alternatively, as stated hereinabove, the HPPE material can be packed between dry (non-impregnated) layers of fire resistant material, and then the resulting structure is enclosed within an outer water resistant cover 18, such as Nylon 6 or 66 impregnated with polyurethane. The edges of outer cover 18 are sealed, as with a water-resistant sealing tape, as known in the art.

Another alternative (not shown) is packing the HPPE material first within a cover of water resistant material. The covered HPPE material is then enclosed between layers of fire resistant material that was impregnated with fire retardant compound, such as polyethylene, and cured.

The produced material can be used, by itself, as a protecting means, or can be further stylized to form garments, blankets, vehicle shield, or any other textile product for anti-fragmentation use.

EXAMPLE HPPE felt of 1200 gr/m2 is enclosed within aramid TM2® of 220 gr/m2. The aramid structure is then covered by a water resistant Nylon 6 fabric of 60gr/m2 . The Nylon cover is sealed by a sealing tape.

The product according to this example weighs about 1800 gr per square meter. It was tested under MIL-P-46593 and MIL-STD-662E standards and affords protection against 17 grain fragments having a velocity (V50) of about 450 m/sec.

It will be appreciated by those skilled in the art that the invention is not limited to what has been shown and described hereinabove by way of example. Rather, the scope of the invention is defined solely by the claims which follow.

Claims (20)

1. An improved anti-fragmentation material comprising: at least one layer of HPPE (High-performance polyethylene) material sandwiched between fire resistant and anti-fragmentation layers.

2. The anti-fragmentation material as in claim 1 wherein said HPPE material is an HPPE felt.

3. The anti-fragmentation material as in claim 1 or 2 wherein said fire resistant material further includes sealing providing water resistance to said fire resistant material

4. The anti-fragmentation material as in claim 3 wherein said sealing means includes material for impregnation and curing in the fire resistant material.

5. The anti-fragmentation material as in claim 3 wherein said sealing means includes a water-resistant fabric enclosing said fire resistant material.

6. The anti-fragmentation material as claimed in any of claims 1-5 wherein said fire resistant material is a unidirectional material.

7. The anti-fragmentation material as claimed in any of claims 1-6 wherein said fire resistant material is an aramid.

8. The anti-fragmentation material as claimed in claim 7 wherein said fire resistant material is unidirectional and of 0/90 structure.

9. The anti-fragmentation material as claimed in any of claims 1-8 wherein said HPPE material includes more than one layer.

10. The anti-fragmentation material as claimed in any of claims 1-9 wherein the weight density of said HPPE material is above 600 gr/m .

11. The anti-fragmentation material as claimed in any of claims 3, 5- 10 wherein said sealing means is Nylon 6 or 66 impregnated with polyurethane.

12. The anti-fragmentation material as claimed in any of claims 1- 11 wherein said sealing means further includes sealing closure means such as a water-resistant sealing tape.

13. A method of manufacturing an anti-fragmentation material comprising the steps: cutting first and second layers of fire resistant material; packing a selected amount of HPPE (High performance polyethylene) material between said first and second layers of said fire resistant material; and sealing said fire resistant material to form a water-resistant anti-fragmentation material. 127528/2 9

14. The method of manufacturing an anti fragmentation material as in claim 13 wherein the steps of sealing includes: - impregnating said fire resistant material with a water resistant compound and then curing the impregnated material, after said step of cutting; and - closing said first and second layers about the HPPE material after said step of packing.

15. The method of manufacturing an anti fragmentation material as in claim 14 wherein said step of closing includes sealing the edges of said first and second layers by means of a sealing tape to form a water resistant closure.

16. The method of manufacturing an anti fragmentation material as in claim 13 wherein the step of sealing said fire resistant material includes: providing an outer water resistant cover; and sealing the edges of said outer water resistant cover around said fire resistant material.

17. The method of manufacturing an anti fragmentation material as in any of claims 13-16 further including the step of providing a water resistant cover around the HPPE material.

18. The anti fragmentation material as claimed in any of claims 1-12 and substantially as shown and described hereinabove. 127528/2 10

19. The anti fragmentation material as claimed in any of claims 1-12 and substantially as illustrated in any of the drawings.

20. The method of manufacturing the anti fragmentation material as claimed in any of claims 13-17 and substantially as illustrated in any of the drawings. The method as claimed in any of claims 13-17 and substantially shown and described hereinabove. \\TLVl\DATA\Winword\david\FormsCovsEtc4-5-6=2002\446-98tOArepSheets.docs