Process for manufacturing an anti-ballistic article
The invention relates to anti-ballistic articles comprising a stack of sheets, each sheet having one or more mono-layers of polyethylene anti-ballistic fibers and a thermoplastic binder, wherein the specific energy absorption (SEA) of the anti-ballistic article is greater than 145 J/kg/m 2 and the maximum % thickness increase, measured at about 90° C., is less than 8% after storing the article for 160 hours at 90° C.
1. An anti-ballistic article comprising a vacuum compressed stack of sheets, each sheet comprising one or more mono-layers of polyethylene anti-ballistic fibers and a thermoplastic binder, wherein the specific energy absorption (SEA) of the anti-ballistic article is greater than 145 J/kg/m 2 and the maximum % thickness increase, measured at about 90° C., is less than 8% after placing the article on a tray in an oven for 160 hours at 90° C.
2. The anti-ballistic article according to claim 1 , wherein the specific energy absorption (SEA) of the anti-ballistic article is greater than 147 J/kg/m 2 .
3. The anti-ballistic article according to claim 1 , wherein the specific energy absorption (SEA) of the anti-ballistic article is greater than 151 J/kg/m 2 .
4. The anti-ballistic article according to claim 1 , wherein the specific energy absorption (SEA) of the anti-ballistic article is greater than 153 J/kg/m 2 .
5. The anti-ballistic article according to claim 1 , wherein the maximum % thickness increase, measured at about 90° C., is less than 7.5% after placing the article on a tray in an oven for 160 hours at 90° C.
6. The anti-ballistic article according to claim 5 , wherein the maximum % thickness increase, measured at about 90° C., is less than 7.0% after placing the article on a tray in an oven for 160 hours at 90° C.
7. The anti-ballistic article according to claim 5 , wherein the maximum % thickness increase, measured at about 90° C., is less than 6.5% after placing the article on a tray in an oven for 160 hours at 90° C.
8. The anti-ballistic article according to claim 5 , wherein the maximum % thickness increase, measured at about 90° C., is less than 6.0% after placing the article on a tray in an oven for 160 hours at 90° C.
9. The anti-ballistic article according to claim 1 , wherein the weight per unit area of the anti-ballistic fiber in the sheet or monolayer ranges from 5 to 250 g/m 2 .
10. The anti-ballistic article according to claim 1 , the article comprising at least 40 sheets.
11. The anti-ballistic article according to claim 1 , wherein the polyethylene anti-ballistic fibers are in the form of tapes.
12. The anti-ballistic article according to claim 1 , wherein the amount of thermoplastic binder is less than 20 wt %.
13. The anti-ballistic article according to claim 12 wherein the thermoplastic binder is chosen from thermoplastic polymer polyurethanes, polyvinyls, polyacrylics, polyolefins and thermoplastic elastomeric block copolymers, polyisopropene-polyethylene-butylene-polystyrene, polystyrene-polyisoprene-polystyrene block copolymers.
14. The anti-ballistic article according to claim 12 wherein the thermoplastic binder binder has a tensile modulus (determined in accordance with ASTM D638, measured at 25° C.) of at least 250 MPa.
15. The anti-ballistic article according to claim 1 , wherein the article has an areal density of at least 2 kg/m 2 .
16. The anti-ballistic article according to claim 15 , wherein the areal density of the article is at least 6 kg/m 2 .
17. The anti-ballistic article according to claim 15 , wherein the areal density of the article is at least 15 kg/m 2 .
18. The anti-ballistic article according to claim 1 , wherein the fibers in a mono-layer are unidirectionally oriented.
19. The anti-ballistic article according to claim 1 , wherein the fibers in a mono-layer are woven.
20. The anti-ballistic article according to claim 18 , further comprising at least one woven sheet with anti-ballistic fibers.