Thermal stability of ion-exchange Nafion N117CS membranes

Iwai, Yasunori; Yamanishi, Toshihiko

The effect of exchanged ions on the thermal stability of Nafion N117CS membranes was investigated. The ion exchange of alkaline metal ions was effective in improving the thermal stability of the Nafion N117CS membrane. We confirmed that the Na-exchange Nafion N117CS membrane possessed a distinctive degree of thermal stability among the alkaline ion-exchange Nafions. Thermal stability improved the most when the Nafion membrane was exchanged for alkaline ions, followed by divalent ions, then trivalent ions. As for the Nafion membrane when it was exchanged for divalent ions or trivalent ions, Nafion following the ion exchange had a thermal stability proportional to an increase in the ionic radius of the cation. The activation of molecular mobility in Nafion was observed between the decomposition stages of the loss of water and the loss of sulfonic groups. The temperature of activation of cation-exchange Nafion became much higher than that of Nafion in an acid form.