THERMAL-STABILITY OF STYRENE GRAFTED AND SULFONATED PROTON CONDUCTINGMEMBRANES BASED ON POLY(VINYLIDENE FLUORIDE)

The thermal stability of styrene grafted and sulfonated poly(vinyliden e fluoride), PVDF-g-PSSA, proton conducting membranes has been studied using thermal gravimetric analysis in combination with mass spectrome try and thermochromatography. The matrix polymer, PVDF, and the non-su lfonated counterpart, PVDF-g-PS, were studied as reference materials. It was found that the degradation of the PVDF-g-PS membrane proceeds i n two steps starting at ca. 340 degrees C with the evolution of degrad ation products typical of polystyrene. The PVDF-g-PSSA membranes are s table to around 270 degrees C even in a strongly oxidising atmosphere. The degradation starts with the simultaneous evolution of water and s ulfur dioxide. The polystyrene grafts start decomposing at 340 degrees C in the PVDF-g-PSSA membranes. Thus the Inetnbranes are suitable for tests in electrochemical applications at elevated temperatures.