Preparation of proton exchange membranes based on crosslinked polytetrafluoroethylene for fuel cell applications

• Published in: Polymer (Guilford) 2004-09, Vol.45 (19), p.6569-6573
• Main Authors: Yamaki, Tetsuya, Kobayashi, Kazuhiro, Asano, Masaharu, Kubota, Hitoshi, Yoshida, Masaru
• Format: Article
• Language: English
• Subjects: Applied sciences; Crosslinked polytetrafluoroethylene; Exact sciences and technology; Exchange resins and membranes; Forms of application and semi-finished materials; Polymer industry, paints, wood; Proton exchange membrane; Radiation grafting; Technology of polymers
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/j.polymer.2004.07.048

We prepared proton exchange membranes by the γ-ray-induced post grafting of styrene into crosslinked polytetrafluoroethylene (PTFE) films and subsequent sulfonation. The degree of grafting was controlled in the range of 7–75% by the crosslinking density of the PTFE matrix as well as the grafting conditions. Under our preparation conditions, the films at the grafting yield of ≥30% were found to produce ion exchange membranes with a homogeneous distribution of sulfonic acid groups. The resulting membranes showed a large ion exchange capacity up to 2.9 meq g −1, which exceeded the performance of commercially available perfluorosulfonic acid films such as Nafion; nevertheless, they appeared to be dimensionally stable in water. These should undoubtedly result from the use of the crosslinked PTFE films as graft substrates and make our ion exchange membranes promising for applications to polymer electrolyte fuel cells.