γ-Ray Induced Graft Copolymerization

IV. Graft Copolymerization of Methacrylic Acid to Polyethylene by Mutual Graft Technique

Abstract

The grafted film was prepared by γ-irradiation of polyethylene film immersed in methanol solution of methacrylic acid. The photomicrograph of cross section of the grafted film demonstrated that the initial grafting took place predominantly at the surface, and as the copolymerization proceeded the grafted layer served as the matrix for further grafting. The plots of the weight of polyethylene grafted versus time showed an approximately linear increase with time. On the other hand, the weight ratio of branch to trunk of the graft copolymers as well as the molecular weight of polymethacrylic acid occluded in the films increased extremely with time. This increase of the grafting rate was explained by “gel effect” in swollen surface layer of the film. The amount of polymethacrylic acid grafted in benzene-methanol was greater than that in methanol. Structual characterization of the graft copolymers and the influences of thickness of polyethylene film, monomer concentration and dose rate on the rate of grafting, were discussed, and the electric surface resistance of the grafted film was also measured.