Thermal stability of radiation grafted PTFE-g-polystyrene sulfonic acid membranes

The thermal stability of radiation grafted PTFE-g-polystyrene sulfonic acid obtained by grafting of styrene onto PTFE films followed by sulfonation wa s studied using thermal gravimetric analysis (TGA) and oven heat treatment under nitrogen atmosphere. The TGA results were analyzed in correlation wit h the membrane two-step preparation procedure and the variation of the degr ee of grafting. The membranes were found to undergo a three-step degradatio n pattern due to dehydration, desulfonation, and decomposition of the PTFE matrix. The effect of desulfonation on some physico-chemical properties of the membranes such as ion exchange capacity and water uptake was investigat ed with respect to the degree of grafting, the temperature and the time of heat treatment. (C) 2000 Elsevier Science Ltd. All rights reserved.