Material sheet and process for its preparation
Material sheets are provided which include at least one monolayer, wherein the at least one monolayer has a plurality of drawn unidirectional polymer fibers having a strength of greater than 1.2 GPa and a thickness of less than 100 μm, and wherein the material sheet includes a bonding agent of less than 13 wt % relative to the total weight of the material sheet.
1. A process for the production a material sheet comprising the step of:
(a) unidirectionally aligning a plurality of drawn polymer fibers having a strength of greater than 1.2 GPa in abutting lengthwise contact with one another to thereby form a monolayer having a thickness of less than 100 μm and a bonding agent content of less than 13 wt % relative to the weight of the material sheet; and
(b) compressing the material sheet to cause adjacent fibers to be mechanically fused to one another along the abutting lengthwise contact thereof.
2. The process according to claim 1 , further comprising prior to step (b) the steps of:
(a1) repeating step (a) thereby producing at least two monolayers, and
(a2) stacking each monolayer such that the fiber direction in adjacent monolayers differs.
3. The process according to claim 1 , wherein
step (a) comprises aligning the drawn polymer fibers such that at least a portion of the fibers within at least one monolayer are in abutting contact along substantially an entire length of the fibers, and wherein
step (b) comprises compressing the material sheet under at least 75 bar pressure such that the abutting fibers are mechanically fused together, thereby forming the material sheet.
4. The process according to claim 1 , wherein the process comprises subjecting the material sheet to pressure and temperature conditions such that less than 5 wt % of the fibers within the material sheet have melted during the process as determined by DSC (10° C./min).
5. The process according to claim 1 , wherein the process comprises subjecting the material sheet to pressure and temperature conditions such that there is no detectable melt bonding as determined by DSC (10° C./min).
6. The process according to claim 1 , wherein each of the thickness of the monolayer is no more than 2 times a thickness of the unidirectionally aligned polymer fibers.
7. The process according to claim 1 , wherein step (a) is practiced such that the monolayer comprises less than 10 wt % of the bonding agent.
8. The process according to claim 1 , which further comprises providing the bonding agent as bonding strips or fibers to bond the fibers in the monolayer.
9. The process according to claim 8 , which further comprises orienting the bonding strips or fibers in a different direction than the unidirectionally aligned polymer fibers within the monolayer.
10. The process according to claim 8 , which comprises covering no more than 20% of a surface area of the monolayer surface area with the bonding strips or fibers.
11. The process according to claim 1 , wherein step (b) is practiced such that the adjacent fibers are mechanically fused along at least 40% of an abutting length thereof.
12. The process according to claim 1 , wherein step (b) is practiced such that the adjacent fibers are mechanically fused along at least 60% of an abutting length thereof.
13. The process according to claim 1 , wherein step (b) is practiced such that the adjacent fibers are mechanically fused along at least 80% of an abutting length thereof.
14. The process according to claim 1 , wherein step (b) is practiced such that the adjacent fibers are mechanically fused along at least 90% of an abutting length thereof.
15. The process according to claim 1 , wherein step (b) is practiced such that the adjacent fibers are mechanically fused along at least 95% of an abutting length thereof.