Mutilayered material sheet and process for its preparation
The invention relates to a multilayered material sheet comprising a consolidated stack of unidirection monolayers of drawn ultra high molecular weight polyolefine. The draw direction of two subsequent monolayers in the stack differs. Moreover the thickness of at least one monolayer does not exceed 50 μm, and the strength of at least one monolayer is comprised between 1.2 GPa and 3 GPa. The invention also relates to a ballistic resistant article comprising the multilayered material sheet and to a process for the preparation of the ballistic resistant article.
1. A multilayered material sheet comprising a consolidated stack of unidirectional monolayers produced from a plurality of drawn ultra high molecular weight polyolefin tapes, wherein a draw direction of two subsequent monolayers in the stack differs, and wherein an areal density of at least one monolayer is between 3 and 200 g/m 2 and an areal density of at least one drawn ultra high molecular weight polyolefin tape is between 10 and 80 g/m 2 , and wherein at least one monolayer of the stack has a strength which is at least 1.2 GPa, and wherein the plurality of drawn tapes are aligned in the same direction and adjacent ones of the tapes do not overlap.
2. The material sheet according to claim 1 , wherein the areal density of the tape is between 15 and 60 g/m 2 .
3. The material sheet according to claim 1 , wherein the polyolefin is ultrahigh molecular weight polyethylene (UHMWPEI and the areal density of the tape is less than 50 g/m 2 .
4. The material sheet according to claim 1 , wherein the areal density of the at least one unidirectional monolayer is between 5 and 120 g/m 2 .
5. The material sheet according to claim 1 , wherein the areal density of the at least one monolayer is between 10 and 80 g/m 2 .
6. The material sheet according to claim 1 , wherein the at least one monolayer has a thickness which does not exceed 29 μm.
7. The material sheet according to claim 1 , wherein the at least one monolayer has a strength which is between 1.2 GPa and 3 GPa.
8. The material sheet according to claim 1 , wherein the polyolefin comprises ultra high molecular weight polyethylene.
9. The material sheet according to claim 1 , wherein two subsequent monolayers in the stack have respective draw directions which differ by an angle α of between 45 and 135°.
10. The material sheet according to claim 1 , wherein the at least one monolayer comprises gel-spun polyolefin tapes having a width of at least 2 mm and an areal density of between 3 and 200 g/m 2 .
11. The material sheet according to claim 1 , wherein the at least one monolayer comprises a plurality of unidirectional tapes of the drawn polyolefin, and wherein the unidirectional tapes form a woven fabric.
12. A ballistic resistant article comprising the material sheet according to claim 1 .
13. The ballistic resistant article according to claim 12 , comprising at least 10 unidirectional monolayers.
14. The ballistic resistant article according to claim 12 , comprising a further sheet of material selected from the group consisting of ceramic, steel, aluminum, magnesium titanium, nickel, chromium and iron or their alloys, glass and graphite, or combinations thereof.
15. The ballistic resistant article according to claim 14 , wherein the further sheet of material has a thickness which is at most 50 mm.
16. The ballistic resistant article according to claim 14 , further comprising a bonding layer between the further sheet of material and the material sheet, wherein the bonding layer comprises a woven or non woven layer of inorganic fiber.