Cation exchange membranes by radiation-induced graft copolymerization of styrene onto PFA copolymer films. III. Thermal stability of the membranes

Thermal stability of cation exchange, PFA-g-polystyrene sulfonic acid membr anes prepared by radiation-induced graft copolymerization of styrene onto P FA films followed by sulfonation was studied by thermal gravimetric analysi s (TGA) and oven heat treatment. The tested samples included original and g rafted PFA films as reference materials. All the membranes showed multistep decomposition patterns due to dehydration, desulfonation, dearomatization, and decomposition of the PFA matrix. Investigations of the individual deco mposition behaviors showed that the weight loss strongly depends upon the d egree of grafting. However, the decomposition temperatures were found to be independent of the degree of grafting. The loss in some selected membrane properties such as ion exchange capacity and water uptake was found to be f unction of the degree of grafting, temperature, and the time of heat treatm ent. (C) 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1877-1885, 2000.