THERMAL-STABILITY OF PROTON-EXCHANGE MEMBRANES PREPARED BY GRAFTING OF STYRENE INTO PRE-IRRADIATED FEP FILMS AND THE EFFECT OF CROSS-LINKING

The thermal stability of crosslinked ion exchange membranes, prepared by pre-irradiation grafting of styrene into FEP films in the presence of divinylbenzene (DVB) as a crosslinker and subsequent sulfonation of the grafted films, was investigated by thermogravimetry. The formatio n of different fragments with increasing temperature was monitored by FTIR. Pre-irradiation leads to destabilization of the FEP backbone, sh owing both earlier depolymerization and substantial redistribution of monomer formation between the two main degradation steps. The presence of DVB had clear effects on the thermal degradation pattern of the su lfonated graft copolymer membrane. Desulfonation occurred at a lower t emperature whereas dearomatization was observed to shift to higher tem peratures.