Radiation-induced crosslinking of Nafion N117CS membranes

Iwai, Yasunori; Hiroki, Akihiro; Tamada, Masao

The successful formation of radiation-induced crosslinking in Nafion N117CS membranes was clearly demonstrated by tensile testing, a methanol uptake measurement, thermo-mechanical analysis (TMA) and fluorine-19 MAS NMR (F NMR). The possibility of radiation-induced crosslinking of Nafion never had been considered with regard to the thermal stability of Nafion membranes, since the scission of PFAE pendant-chains in Nafion membranes in their protonated form begins at 523 K. To improve the thermal stability of Nafion membranes, Nafion membranes were soaked in sodium chloride prior to irradiation. The sodium-exchange Nafion membranes were irradiated with rays in an argon atmosphere at temperatures ranging from room temperature to 618 K. The irradiated membranes were re-exchanged to the protonated form. Fluorine-19 MAS NMR results for the alcohol-swollen membranes indicate peaks which originated due to radiation-induced crosslinking. An increase in percent elongation at break, a decrease in methanol uptake, and a decrease in the softening temperature at a differential TMA peak for membranes irradiated at 598 K compared to received membranes also add support for our new finding.