Preparation of ETFE-based fuel cell membranes using UV-induced photografting and electron beam-induced crosslinking techniques

Chen, J.; Asano, Masaharu; Maekawa, Yasunari; Sakamura, Takahiro*; Kubota, Hitoshi*; Yoshida, Masaru

A novel process comprising UV-induced photografting of styrene into poly(tetrafluoroethylene-co-ethylene) (ETFE) films in vapor and liquid phases, followed by electron beam-induced crosslinking has been developed for preparing polymer electrolyte membranes. The significance of this process is that the photografted polystyrene chains can completely penetrate into the base ETFE film; the membranes show proton conductibility available for fuel cell applications. On one hand, the proton conductivity of the liquid-phase photografted electrolyte membranes is higher than the vapor-phase one, and is anisotropic in the surface and thickness directions. On the other hand, radiation-induced crosslinking greatly improves the chemical stability of the resultant fuel cell membranes, and maintains the surface concentration of sulfonic acid groups at its higher level.