Polymer electrolyte membrane
The present invention provides a polymer electrolyte membrane having excellent strength, a small dimensional change, and a low membrane resistance. The polymer electrolyte membrane includes a porous film and a polymer electrolyte. The porous film has a fibril/node area ratio of 90/10 to 75/25.
1. A polymer electrolyte membrane comprising:
a porous film; and
a polymer electrolyte,
the porous film having a fibril/node area ratio of 90/10 to 75/25 and a contact angle with a solution of the polymer electrolyte of 44 degrees or smaller,
wherein the porous film having a film density of 0.80 g/cm 3 or lower,
wherein the polymer electrolyte is a fluoropolymer electrolyte, wherein the fluoropolymer electrolyte is a copolymer comprising
a repeating unit derived from a COOZ or SO 3 Z group-containing monomer represented by the following formula (I):
CF 2 =CF(CF 2 ) k —O 1 —(CFY 2 ) m -A 1 (I)
wherein k is an integer of 0 to 2; 1 is 0 or 1; m is an integer of 0 to 12, if m=0, then 1=0, when m is an integer of 1 to 12, Y 2 is F or Cl and m Y 2 s may be the same as or different from each other; A 1 is COOZ or SO 3 Z, where Z is an alkali metal, an alkaline earth metal, hydrogen, or NR 1 R 2 R 3 R 4 , where R 1 , R 2 , R 3 , and R 4 are each individually a C1-C3 alkyl group or hydrogen, and
a repeating unit derived from tetrafluoroethylene.
2. The polymer electrolyte membrane according to claim 1 ,
wherein the porous film has a product of vertical and lateral matrix tensile strengths of 2.20×10 4 MPa 2 or greater.
3. The polymer electrolyte membrane according to claim 1 ,
wherein the polymer electrolyte is filled into pores of the porous film, and the porous film is a polytetrafluoroethylene porous film prepared by stretching semi-sintered polytetrafluoroethylene and heat-setting the stretched semi-sintered polytetrafluoroethylene at a temperature of not lower than the melting point of sintered polytetrafluoroethylene.
4. The polymer electrolyte membrane according to claim 1 ,
wherein the porous film has an average pore size of 0.05 μm or greater.
5. The polymer electrolyte membrane according to claim 1 ,
wherein the porous film has a thickness of smaller than 20 μm.
6. The polymer electrolyte membrane according to claim 1 ,
wherein the porous film is a polytetrafluoroethylene porous film and the polytetrafluoroethylene has a standard specific gravity of 2.160 or lower.
7. A membrane electrode assembly comprising the polymer electrolyte membrane according to claim 1 .
8. A polymer electrolyte fuel cell comprising the membrane electrode assembly according to claim 7 .