光グラフト重合を利用したフッ素系高分子電解質膜の開発 Development of Fluorinated Polymer Electrolyte Membranes Using Photografting Methods
Polytetrafluoroethylene (PTFE)-based polymer electrolyte membranes were developed by radiation-grafting of styrene onto PTFE films and subsequent sulfonation. However, the PTFE is a radiation-degradation material. To overcome this disadvantage, we introduced the γ-crosslinked structure into the PTFE to increase its radiation-resistance before grafting. On the contrary, the UV method is very useful as an irradiation source for grafting. Under the UV irradiation, the mechanical properties of the PTFE films were almost not affected, while the radicals were generated on the surface of the film. The surface radicals initialed the styrene grafting, and the graft chains were readily propagated into the PTFE films. The resultant grafted films were sulfonated to obtain the polymer electrolyte membranes. Even through the degree of grafting was lower than 10%, the proton conductivity of the newly prepared electrolyte membranes can reach a value similar to Nafion. In comparison with γ-ray radiation grafting, the photografting technique is very simple and safe, and causes less damages to the membranes because the significant degradation of the PTFE main chains can be avoided.
膜 33(2), 63-69, 2008-03-01
THE MEMBRANE SOCIETY OF JAPAN