Tape and products containing the same
The invention relates to a fibrous tape comprising fused polymeric fibers, said fibrous tape having a tape thickness and a tape width and being characterized by a coefficient of variation (CV) of the tape thickness across the tape width of at most 6%.
1. A fibrous tape comprising fused polymeric fibers, wherein at least 75 mass % of the fused polymeric fibers are oriented so as to be substantially in parallel along a common direction, and wherein
the polymeric fibers have a fiber length and abutting ones of the polymeric fibers are fused to each other over an abutting length of at least 50% of the fiber length, and wherein
the fibrous tape has a tape thickness from 1 μm to 200 μm, a tape width, and a coefficient of variation (CV) of the tape thickness across the tape width of at most 6%, wherein the CV of the tape thickness is calculated by:
(i) obtaining a cross section of the tape by embedding the tape in epoxy resin and cutting slices of the embedded tape-resin system;
(ii) selecting an enlargement using a microscope such that the width of the tape is equal to about 40 times the thickness of the tape;
(iii) taking 5 measurements of the local thickness of the tape, evenly distributed across the width of the tape; and
(iv) dividing the standard deviation of the 5 measurements by the average of the 5 measurements.
2. The tape of claim 1 , wherein the CV of the tape thickness across the tape width is at most 3%.
3. The tape of claim 1 , wherein the ratio of width to thickness of the tape is at least 5:1.
4. The tape of claim 1 , wherein the width of the tape is between 1 mm and 2000 mm.
5. The tape of claim 1 , wherein the polymeric fibers are polyolefin fibers.
6. The tape of claim 5 , wherein the polyolefin fibers are polyethylene fibers.
7. The tape of claim 5 , wherein the polyolefin fibers are ultrahigh molecular weight polyethylene ([U]HMWPE) fibers.
8. The tape of claim 1 , wherein the tensile strength of the polymeric fibers is at least 1.2 GPa.
9. The tape of claim 1 , wherein the tensile modulus of the polymeric fibers is at least 5 GPa.
10. The tape of claim 1 , wherein the tape has a tensile strength of at least 1 GPa.
11. The tape of claim 1 , wherein the tape has a tensile modulus of at least 60 GPa.
12. A panel comprising a stack of two or more sheets comprising monolayers which include a fibrous tape of claim 1 .
13. A product comprising a fibrous tape of claim 1 , wherein the product is selected from the group consisting of automotive products, marine products, aerospace products, life-protection products and architectural products.
14. The product according to claim 13 , wherein the product is a product for ships, boats, marine panels, planes, helicopters, aerospace panels, body armor, ballistic vests, ballistic shields, ballistic helmets, ballistic vehicle protection, windows, doors, walls, cargo doors, cargo walls, radomes and shields.
15. A process for the manufacturing of a tape according to claim 1 , comprising the steps of:
(a) providing a plurality of polymeric fibers having a melting temperature Tm;
(b) forming a layer comprising a network of polymeric fibers;
(c) introducing the layer into a nip of a calendar and calendaring the layer with a calendaring line-pressure of at least 100 N/mm, at a temperature of below Tm of the polymeric fibers to form a tape comprising fused polymeric fibers; and
(d) cooling the tape.
16. The process of claim 15 , wherein step (d) includes cooling the tape to room temperature.
17. The process according to claim 15 , wherein the plurality of polymeric fibers are in the form of an ordered parallel array.
18. The process according to claim 15 , wherein step (b) comprises forming the layer comprising an abutting and unidirectionally aligned network of the polymeric fibers.
19. The process according to claim 18 , wherein the polymeric fibers forming the abutting and unidirectionally aligned network of the layer are grouped into a plurality of yarns, each yarn having a titer of at least 220 dtex.