Process for improving interfacial adhesion in a laminate
A method for improving adhesion between two adjacent layers of a laminate membrane includes annealing the laminate membrane at a temperature between an α-transition temperature and a β-transition temperature of at least one polymeric component of at least one of two adjacent layers for a time sufficient for the at least one polymeric component of at least one of the adjacent layers to partially diffuse into the other adjacent layer. A sealed, inflated bladder of the invention prepared from the laminate membrane can experience high strains without layer separation or peeling of the laminate layers, even at a seam.
1. A method for improving adhesion between two adjacent layers of a laminate membrane, comprising the steps of:
(a) forming a laminate having a first thermoplastic layer adjacent to a second thermoplastic layer and having an interfacial boundary between the first thermoplastic layer and the second thermoplastic layer;
(b) after a lag time when the laminate is below a temperature at which significant diffusion across the interfacial boundary takes place, annealling the laminate at least one temperature between an α-transition temperature and a β-transition temperature of at least one polymeric component of at least one of the layers for a time sufficient for the at least one polymeric component to partially diffuse into the adjacent layer.
2. A method according to claim 1 , wherein the laminate is shaped with heat during the annealing step.
3. A method according to claim 1 , wherein the annealing step takes place immediately after a step of forming the laminate into a desired shape.
4. A method according to claim 1 , wherein the annealing step is carried out for a time sufficient to produce an interfacial adhesion strength of at least about 20 pounds per linear inch.
5. A method according to claim 1 , wherein one of the layers has a semi-crystalline polymer and the annealing step (b) is carried out at one or more temperatures between an α-transition temperature and a β-transition temperature of the semi-crystalline polymer.
6. A method according to claim 1 , wherein the annealing step (b) increases the peel strength between the layer and the adjacent layer by at least about 100%.
7. A method according to claim 1 , wherein the annealing step (b) increases the peel strength between the layer and the adjacent layer by at least about 500%.
8. A method according to claim 1 , wherein the laminate has at least three layers and further wherein during the diffusion occurs at two or more interfaces between layers.
9. A method according to claim 1 , wherein a polymeric material of the adjacent layer has molten regions at the annealing temperature or temperatures.
10. A method according to claim 1 , wherein the annealing step (b) is carried out for a time sufficient that the peel strength between the layer and the adjacent layer would increase less than 10% if annealed for another hour.
11. A method according to claim 1 , wherein the polymeric component comprises a thermoplastic gas barrier polymer and the adjacent layer comprises a thermoplastic elastomer.
12. A method according to claim 11 , wherein the thermoplastic elastomer comprises a material selected from the group consisting of polyurethanes prepared using polyester, polyether, and polycarbonate diols, flexible polyolefins, styrenic thermoplastic elastomers, polyamide elastomers, polyamide-ether elastomers, polymeric ester-ether elastomers, flexible ionomers, thermoplastic vulcanizates, vulcanized EPDM in polypropylene, flexible poly(vinyl chloride) homopolymers and copolymers, flexible acrylic polymers, and combinations thereof.
13. A method according to claim 11 , wherein the thermoplastic elastomer comprises a polyurethane prepared form a polyester diol.
14. A method according to claim 11 , wherein the thermoplastic gas baffler polymer comprises a material selected from the group consisting of ethylene-vinyl alcohol copolymers, vinylidene chloride polymer, acrylonitrile polymer, copolymers of acrylonitrile and methyl acrylate, semicrystalline polyesters, polyethylene terephthalate, polyamides, crystalline polymers, epoxy resins based on N,N-dimethylethylenediamine and resorcinol, polyurethane engineering thermoplastics, and combinations thereof.
15. A method according to claim 11 , wherein the thermoplastic gas barrier polymer comprises an ethylene-vinyl alcohol copolymer.
16. A method according to claim 1 , wherein the laminate membrane has at least one layer comprising an ethylene-vinyl alcohol copolymer and at least two layers comprising thermoplastic elastomer adjacent to the ethylene-vinyl alcohol copolymer layer, and wherein the annealing step (b) is carried out at one or more temperatures between an α-transition temperature and a β-transition temperature of the ethylene-vinyl alcohol copolymer.
17. A method according to claim 16 , wherein the laminate membrane has outer layers that are at least about 125 microns thick.
18. A method according to claim 1 , wherein the laminate membrane has a layer of a microlayer polymeric composite, wherein the microlayer polymeric composite has alternating layers of at least one polymeric fluid barrier material and at least one thermoplastic elastomeric material.
19. A method according to claim 1 , including a further step of forming the laminate membrane into a desired shape.
20. A method according to claim 19 , wherein the laminate membrane is formed into the desired shape with heat.
21. A laminate membrane produced by the method of claim 1 .
22. An inflated bladder, wherein said bladder is formed by sealing and inflating a laminate membrane according to claim 21 .
23. An inflated bladder according to claim 22 , wherein said bladder is inflated with gas comprising a member selected from the group consisting of air and nitrogen.
24. An article comprising a laminate membrane according to claim 21 .