Poly(ethylene-co-tetrafluoroethylene) (ETFE)-based graft-type polymer electrolyte membranes with different ion exchange capacities; Relative humidity dependence for fuel cell applications

Tran, D. T.; Sawada, Shinichi; Hasegawa, Shin; Katsumura, Yosuke*; Maekawa, Yasunari

Relative humidity (RH) dependence of the proton conduction and mechanical properties of poly(ethylene-co-tetrafluoroethylene) (ETFE)-based radiation grafted polymer electrolyte membranes (PEMs) were investigated in a wide ion exchange capacity (IEC) range at 80 C. The proton conductivities of the ETFE-based PEMs for IECs of 1.3-2.9 mmol/g were 0.001-0.013 S/cm at 30% RH. These PEMs have conductivities that are less dependent on RH than aromatic-hydrocarbon-polymer based PEMs. The ETFE PEM (IEC 2.4 mmol/g) showed higher tensile strength than Nafion at 100% RH. It was revealed that the mechanical strength and proton conductivity were clearly related to PEM crystallinities.