Preparation of crosslinked fluoropolymer electrolyte membranes for use in fuel cells and then investigated their structural properties

Inoue, Yutaka; Kobayashi, Kazuhiro; Yamaki, Tetsuya; Asano, Masaharu; Kubota, Hitoshi*; Yoshida, Masaru

We prepared crosslinked fluoropolymer electrolyte membranes for use in fuel cells and then investigated their structural properties by X-ray diffraction (XRD) analysis. The radiation-induced grafting of styrene into crosslinked polytetrafluoroethylene (PTFE) films and subsequent sulfonation enabled us to obtain the electrolyte membrane with a sufficient ion exchange capacity, which exceeds that of the commercially-available film, Nafion. As the crosslinking and styrene grafting reactions proceeded, the size of the PTFE crystallites in the film became smaller, thereby decreasing the film crystallinity. Interestingly, in contrast to Nafion, the resulting sulfonated membranes were found to have high crystallinity.