Sealing of a membrane electrode assembly
A sealed and/or reinforced membrane electrode assembly is disclosed. Encapsulation films, each comprising a backing layer and an adhesive layer, are positioned on the edges of at least one face of each gas diffusion substrate such that the adhesive layers impregnate into each gas diffusion substrate. Methods of forming sealed and/or reinforced membrane electrode assemblies are also disclosed.
1. A membrane electrode assembly comprising a polymer electrolyte membrane, electrocatalyst layers disposed on either side of the membrane and gas diffusion substrates contacting each of the electrocatalyst layers, wherein encapsulation films, each comprising a backing layer and an adhesive layer, are positioned on the edges of at least one face of each gas diffusion substrate such that the adhesive layers impregnate only part way through the thickness of each gas diffusion substrate and wherein the adhesive layer comprises a hot-melt adhesive.
2. A membrane electrode assembly according to claim 1 , wherein the backing layers contact the at least one face of each gas diffusion substrate.
3. A membrane electrode assembly according to claim 1 , wherein the thickness of the backing layer is between 5 μm and 50 μm.
4. A membrane electrode assembly according to claim 1 , wherein the thickness of the adhesive layer is from 1 μm to 300 μm.
5. A membrane electrode assembly according to claim 1 , wherein the encapsulation films are positioned on the outer faces of the gas diffusion substrates.
6. A membrane electrode assembly according to claim 5 , wherein the adhesive layer of the encapsulation film bonds to the membrane.
7. A membrane electrode assembly according to claim 5 , wherein the membrane extends beyond the gas diffusion substrates and the adhesive layers and bonds directly to the protruding membrane.
8. A membrane electrode assembly according to claim 5 , wherein the encapsulation films extend beyond the edges of the gas diffusion substrates and beyond the edge of the membrane, and the adhesive layers of the encapsulating films bond to one another, thus enveloping the membrane edge and substrate edges.
9. A membrane electrode assembly according to claim 1 , wherein the encapsulation films are positioned on the inner faces of the gas diffusion substrates.
10. A membrane electrode assembly according to claim 9 , wherein the encapsulation films have only one adhesive layer and there is no adhesion between the encapsulation films and the membrane.
11. A membrane electrode assembly according to claim 10 , wherein the thickness of the backing film is approximately the same as the thickness of the catalyst layer.
12. A membrane electrode assembly according to claim 9 , wherein the encapsulation film has two adhesive layers, wherein a first adhesive layer impregnates the substrate, and a second adhesive layer adheres to the membrane.
13. A membrane electrode assembly according to claim 12 , wherein the combined thickness of the backing layer and the second adhesive layer is the same as the thickness of the catalyst layer.
14. A membrane electrode assembly according to claim 9 , wherein the adhesive layers impregnate only part way through the thickness of the substrate and the remaining portions of the substrates are impregnated with an elastomeric material.
15. A membrane electrode assembly according to claim 1 , wherein encapsulation films are positioned on the outer and on the inner faces of the gas diffusion substrates.
16. A membrane electrode assembly according to claim 1 , wherein the adhesive layer comprises an adhesive selected from the group consisting of polyethylene-based and polypropylene-based adhesives.
17. A membrane electrode assembly according to claim 1 , wherein the adhesive layer comprises an adhesive selected from the group consisting of a copolymer of ethylene and methacrylic acid and a copolymer of ethylene and vinyl acetate.
18. A membrane electrode assembly according to claim 1 , wherein the adhesive layers bond to the membrane.