Transparent antiballistic article and method for its preparation
The invention relates to a method for the preparation of a transparent antiballistic article. The method comprises providing a plurality of anisotropic polymeric film layers, stacking the film layers to form an assembly and compressing the thus formed assembly at a temperature and pressure sufficient to consolidate the film layers, whereby the temperature is not more than 50° C. below the melting temperature of the polymer, the pressure is at least 80 MPa and sufficiently high to obtain an optical transparency according of at least 50% transmission. The invention also relates to a ballistic resistant article having an energy absorption for 17 grain FSP according to the STANAG 2920 standard of at least 10 J/(kg/m 2 ) and an optical transparency according of at least 50% transmission.
1. A method of preparing a transparent antiballistic article, the method comprising:
(a) providing a plurality of anisotropic polymeric film layers;
(b) stacking the anisotropic polymeric film layers to form an assembly thereof; and
(c) consolidating the film layers by compressing the assembly formed according to step (b) at a temperature which is not more than 50° C. below a melting temperature of the polymer, and at a pressure which is at least 80 MPa to obtain an optical transparency of at least 50%.
2. The method according to claim 1 , which comprises providing a plurality of multilayered material sheets of consolidated stacks of the anisotropic polymeric film layers, and stacking the plurality of multilayered material sheets such that an orientation direction of two subsequent film layers in the stack differs.
3. The method according to claim 1 , wherein the temperature is not more than 10° C. below the melting temperature of the polymer.
4. The method according to claim 1 , wherein the pressure is at least 200 MPa.
5. The method according to claim 1 , wherein the pressure is sufficiently high to obtain an optical transparency of at least 80% transmission.
6. The method according to claim 1 , which comprises applying a vacuum to the assembly before, during or after compressing the assembly according to step (c).
7. The method according to claim 1 , wherein at least one of the anisotropic film layers has a thickness which does not exceed 150 microns.
8. The method according to claim 7 , wherein the thickness of at least one of the anisotropic film layers does not exceed 30 microns.
9. The method according to claim 1 , wherein at least one of the anisotropic film layers has a strength, as measured in direction of greatest strength, which is at least 0.4 GPa.
10. The method according to claim 9 , wherein the strength of at least one of the anisotropic film layers is at least 1.5 GPa.
11. The method according to claim 1 , wherein the polymer is selected from the group consisting of polyolefins, polyesters, polyvinyl alcohols, polyacrylonitriles, polyamides, and polyketone.