Radiation grafting to poly(ethylene terephthalate) fibres

Abstract

Polyethylene terephthalate (PET) monofilaments were grafted with styrene in methylene chloride solution using both the mutual and preirradiation methods. Good yields were obtained, the grafted fibres were dissolved and the graft copolymer and both homopolymers separated by various techniques. The graft copolymers were hydrolysed with potassium hydroxide in benzyl alcohol to destroy the PET backbone. The molecular weights were determined by osmometry. The G values of grafted side chains were 0.57 and 0.10 per 100 eV for the mutual and preirradiation methods, respectively. The corresponding fractions of PET grafted were 0.24 and 0.11. Less than 4% homopolymer was produced by either method. The yields contrast with radical yields measured by e.s.r. of only 0.025. It is suggested that the high grafting yields are due to the methylene chloride facilitating the accessibility of the monomer to the active sites created by the radiation rather than by the increased yields of radicals by chain transfer. Chlorine, for example, did not lead to increased yields even in the presence of methylene chloride. Presumably, in the mutual grafting system, radicals are available for grafting, which are too labile to be detected by e.s.r. In the case of the preirradiation method, the yields are also higher than the radical yields. This may be due to a regenerative chain transfer mechanism.