Radiation-induced grafting of styrene into radiation-modified fluoropolymer films

Poly(tetrafluoroethylene) (PTFE), poly(tetrafluoroethylene-co-hexafluoropropylene) (FEP) and poly(tetrafluoroethylene-co-perfluoropropylvinyl ether) (PFA) films were modified by electron beam irradiation in the molten state. These radiation-modified films and original films were irradiated in vacuum at room temperature to initiate the grafting of styrene in the subsequent step. The grafting of styrene into the fluoropolymer films was proved by FT-IR spectroscopy. The influence of cross-linking dose, grafting dose and grafting time on the yield of grafting was studied. The yield of grafting can be enhanced by the pre-irradiation of the films in the molten state. The change in the geometric dimension of the films caused by grafting was also measured and discussed. The grafted PTFE films were sulfonated by chlorosulfonic acid. The molar ratio of sulfonic acid groups to styrene units was found to be close to unity.