Durability of irradiated polymers in solid-polymer-electrolyte water electrolyzer

Iwai, Yasunori; Yamanishi, Toshihiko; Nishi, Masataka; Yagi, Toshiaki; Tamada, Masao

Radioactive durability of organic polymers in solid-polymer-electrolyte water electrolyzer was investigated by -ray irradiation. Serious deteriorations for tensile strength and ion exchange capacity of ion exchange membrane (Nafion) were not observed up to 850 kGy. No serious damage was also observed for the gasket materials (Aflas) up to 500 kGy. PFA and FEP, insulator materials, lost their tensile strength at 300 kGy or less. As the result, it is concluded that the electrolyzer could be used up to around 500 kGy in the case where PFA and FEP are replaced by the polyimide resin whose durability is well demonstrated. Two degrading mechanisms were supposed. One is direct degradation by energy of radial rays. The other is that by the attack of radicals. It was demonstrated that the effect of radicals on the membrane was not dominant. The quantity of dissolved fluorine in water was found to correlate with the tensile strength and ion exchange capacity. Hence, it is possible to evaluate the degradation of the membrane by monitoring the quantity of dissolved fluorine.