CROSS-LINKED ION-EXCHANGE MEMBRANES BY RADIATION GRAFTING OF STYRENE DIVINYLBENZENE INTO FEP FILMS/

Ion exchange membranes were prepared by simultaneous radiation graftin g of styrene into FEP films and subsequent sulfonation, Divinylbenzene was used as crosslinker in the grafting medium. The distribution of p olystyrene grafts across the membrane matrix was determined by micropr obe measurements. It was observed that for low levels of grafting such as 13%, crosslinked membranes had a better homogeneity in graft distr ibution across its matrix as compared to the non-crosslinked ones. The latter showed a much higher concentration of grafts at the surface th an in the middle of the film. The membrane characteristics, such as sw elling and specific resistivity as a function of the degree of graftin g and crosslinking were evaluated. Membranes showed a sharp decrease i n the resistivity up to similar to 25% grafting, beyond which the decr ease was not significant. The higher the crosslinker content, the high er was the ionic resistivity. A relation between the degree of graftin g and membrane properties, such as degree of swelling and specific res istivity as a function of the crosslinker content was established.