Ballistic-resistant article based on films provided with matrix
A process for manufacturing a ballistic resistant article including steps: a) stacking a stretchable lamina of ultra-high molecular weight polyethylene (UHMWPE) and a stretchable continuous film of a polymer as organic matrix material to form a lamina-film stack, the continuous film not being an UHMWPE film; b) elongating the stack at a temperature below the melting point of the lamina, to an elongation ratio of at least 2, thereby providing a UHMWPE film with an organic matrix material in which the UHMWPE film is co-stretched with the film of polymer as organic matrix material; c) aligning a plurality of films to form a layer of films; d) stacking at least two layers of films to form a sheet; e) stacking a plurality of sheets to form a stack of sheets, and consolidating the sheets prior to and/or after step e) by applying pressure and optionally heat. Also, a ballistic-resistant article.
1. A process for the manufacture of a ballistic resistant article comprising the steps of:
a) stacking a stretchable lamina of ultra-high molecular weight polyethylene (UHMWPE) and a stretchable continuous film of polymer as organic matrix material to form a lamina-film stack, the continuous film of polymer as organic matrix material not being an UHMWPE film,
b) elongating the lamina-film stack formed in step a) at a temperature below the melting point of the stretchable UHMWPE lamina, to an elongation ratio of at least 2, thereby providing a stretched lamina-film stack in which the UHMWPE lamina is co-stretched with the film of polymer as organic matrix material,
c) aligning a plurality of stretched lamina-film stacks provided according to step b) to form a layer of the stretched lamina-film stacks,
d) stacking at least two layers formed according to step c) to form a sheet,
e) stacking a plurality of sheets formed according to step d) to form a stack of the sheets, and
f) consolidating the sheets prior to and/or after stacking the sheets according to step e) by applying pressure and optionally heat.
2. The process of claim 1 wherein the stretchable UHMWPE lamina has a thickness of 50-3000 microns and the stretchable continuous organic matrix polymer film has a thickness of 4-25 microns.
3. The process of claim 1 wherein the melting point of the stretchable organic matrix polymer film is below the melting point of the stretchable UHMWPE lamina and the elongating in step b) is performed at a temperature above the melting point of the stretchable organic matrix polymer film.
4. The process of claim 1 wherein the elongation ratio in step b) is at least 6.
5. The process of claim 1 wherein the elongating in step b) is performed in at least two elongating steps, or in at least three elongating steps.
6. The process of claim 1 comprising consolidating one of the plurality of sheets formed according to step d) individually prior to the stacking in step e) by applying pressure and optionally heat onto the sheet.
7. The process of claim 1 comprising consolidating the stack of sheets formed in step e) as a whole after the stacking in step e) by applying pressure and optionally heat onto the stack of sheets.
8. A ballistic-resistant article comprising:
a stack of sheets, the sheets comprising at least two layers of ultra-high molecular weight polyethylene (UHMWPE) films provided with a continuous film of polymer as organic matrix material,
wherein the UHMWPE films are provided over at least 95% of at least one surface thereof with the continuous film of polymer as organic matrix material, the continuous film of polymer as organic matrix material not being an UHMWPE film,
wherein the UHMWPE films have a thickness of 10-100 microns and the organic matrix polymer film has a thickness of 0.1-3 microns,
wherein the weight percentage of the organic matrix polymer film with respect to the total weight of the organic matrix polymer film and the ultra-high molecular weight polyethylene films is from 0.1 to 3 wt. %,
wherein the sheets in the stack are consolidated, and
wherein an orientation of polymer molecules in the continuous film of polymer as organic matrix material in a first direction of the organic matrix polymer film differs from an orientation of polymer molecules in the continuous film of polymer as organic matrix material in a second direction of the organic matrix polymer film, wherein the first direction of the organic matrix polymer film and the second direction of the organic matrix polymer film are at an angle of 90°.
9. The ballistic-resistant article of claim 8 wherein the UHMWPE films are provided with the continuous film of polymer as organic matrix material over at least 97% of the at least one surface thereof.
10. The ballistic-resistant article of claim 8 wherein the weight percentage of the organic matrix polymer film with respect to the total weight of the organic matrix polymer film and the ultra-high molecular weight polyethylene films is from 0.15 to 2.5 wt. %.
11. The ballistic-resistant article of claim 8 wherein the organic matrix polymer film is a polyethylene film.
12. The ballistic-resistant article of claim 8 wherein the ultra-high molecular weight polyethylene films have a thickness of 20-80 microns, and the organic matrix polymer film has a thickness of 0.15-2.5 microns.
13. The ballistic-resistant article of claim 8 wherein an orientation of the UHMWPE films within each of the layers is unidirectional and, optionally, the orientation of the UHMWPE films in one of the layers is at an angle to the orientation of the UHMWPE films in an adjacent one of the layers.
14. The ballistic resistant article of claim 8 wherein the sheets are individually consolidated.
15. The ballistic resistant article of claim 8 wherein the stack of sheets is consolidated as a whole.