Method of making multilayered polyethylene material and ballistic resistant articles
The present invention relates to polyethylene material that has a plurality of unidirectionally oriented polyethylene monolayers cross-piled and compressed at an angle to one another, each polyethylene monolayer composed of ultra high molecular weight polyethylene and essentially devoid of resins. The present invention further relates to ballistic resistant articles that include or incorporate the inventive polyethylene material and to methods of preparing the material and articles incorporating same.
1. A method for the preparation of a bilayered material comprising a plurality of unidirectional monolayers consisting essentially of ultrahigh-molecular-weight polyethylene and essentially devoid of bonding matrices, with the direction of each monolayer being rotated with respect to the direction in an adjacent unidirectional monolayer, the method comprising:
(a) providing a first unidirectional ultrahigh-molecular-weight polyethylene monolayer;
(b) providing a plurality of unidirectional ultrahigh-molecular-weight polyethylene flat film strips;
(c) aligning the plurality of unidirectional ultrahigh-molecular-weight-polyethylene flat film strips such that each strip is oriented in parallel to adjacent strips such that each strip overlaps with an adjacent strip only along an edge region thereof, said plurality of strips being laid over the first unidirectional ultrahigh-molecular-weight polyethylene monolayer, with the direction of said plurality of strips being rotated with respect to the direction of said first unidirectional ultrahigh-molecular-weight-polyethylene monolayer at an angle; and
(d) compressing said plurality of unidirectional ultrahigh-molecular-weight-polyethylene flat film strips laid over said unidirectional ultrahigh molecular-weight polyethylene monolayer, thereby obtaining a bilayered material consisting essentially of ultrahigh-molecular-weight-polyethylene and essentially devoid of bonding matrices, comprising two compressed unidirectional monolayers with the direction of each monolayer being rotated at an angle with respect to the direction in an adjacent unidirectional monolayer.
2. The method of claim 1 , further comprising:
(e) repeating steps (a) to (d), at least once thereby obtaining a plurality of bilayered materials; and
(f) compressing-molding at least two bilayered materials obtained in step (e) thereby obtaining a multilayered material, with step (e) repeated until the desired number of bilayered materials is obtained.
3. The method of claim 1 , further comprising the step of cutting the multilayered material to a desired shape.
4. A method for preparing a ballistic resistant article, which comprises:
(a) aligning a plurality of unidirectional ultrahigh-molecular-weight polyethylene flat film strips such that each strip is oriented in parallel to adjacent strips, wherein adjacent strips partially overlap only along an edge region thereof, said plurality of strips being laid over a first unidirectional ultrahigh-molecular-weight polyethylene monolayer, with the direction of said plurality of strips being rotated with respect to the direction of said first unidirectional ultrahigh-molecular-weight polyethylene monolayer at an angle; and
(b) compressing said plurality of unidirectional ultrahigh-molecular-weight polyethylene flat film strips laid over said unidirectional ultrahigh-molecular-weight polyethylene monolayer, thereby obtaining a bilayered material consisting essentially of ultrahigh-molecular-weight polyethylene and essentially devoid of bonding matrices, comprising two compressed unidirectional monolayers with the direction of each monolayer being rotated at an angle with respect to the direction in an adjacent unidirectional monolayer, with the bilayered material being essentially devoid of resins or adhesives.
5. The method of claim 4 , which further comprises associating the bilayered material with an additional material selected from the group consisting of ceramic, steel, aluminum, titanium, glass and graphite.