Suitability of some fluoropolymers used as base films for preparation of polymer electrolyte fuel cell membranes

Radiation grafting is a well-established technique for the preparation of polymer electrolyte membranes for fuel cells. The nature of the base films is an important parameter which is in close relation to the properties of the fuel cell membranes. In this study, six commercially available fluoropolymer films, PTFE, FEP, PFA, ETFE, PVDF and PVF films, together with the crosslinked PTFE (cPTFE) films have been studied with respect to their suitability for the preparation of fuel cell membranes. The PTFE and PVF films are not suitable for the preparation of fuel cell membranes. The former is quite unstable for radiation and the latter undergoes only surface grafting. The FEP-based membrane shows the highest proton conductivity over the entire ion exchange capacity range and the lowest water uptake over the entire conductivity range, while the ETFE-based membrane shows the opposite results. Perfluorinated film-based membranes are considerably more chemically stable than the partially fluorinated film-based membranes. However, the latter shows a significantly better mechanical property than the former. It is concluded that the perfluorinated film-based membranes are promising materials for the hydrogen-fed fuel cells, and the partially fluorinated film-based membranes are appropriate for the liquid methanol-fed fuel cells.