Preparation of PFA-g-polystyrene sulfonic acid membranes by the γ-radiation grafting of styrene onto PFA films

Poly(tetrafluoroethylene-co-perfluorovinylether)-g-polystyrene sulfonic acid (PFA-g-PSSA) membranes were prepared by radiation-induced grafting of styrene onto PFA films using a simultaneous irradiation technique and a subsequent sulfonation in a chlorosulfonic acid/dichloroethane mixture. The PFA films were exposed to γ irradiation doses of 50-200 kGy at a dose rate of 10 kGy/h. The physico-chemical properties of the PFA-g-PSSA membranes such as the degree of grafting, ion exchange capacity, water uptake and tensile strength were evaluated. The structure variations after the grafting and sulfonation were investigated using FTIR-ATR spectroscopy. Differential scanning calorimetry and thermogravimetric analysis have been used to study the thermal decomposition and the melting behavior of the grafted PFA films. The as-prepared PFA-g-PSSA membranes in this work showed a good combination of a high ion exchange capacity (1.8-3.25 meq/g), acceptable water uptake (40-70 wt%), low thickness and volume expansion and/or contraction.