1969 Volume 42 Issue 12 Pages 3380-3384
The cobalt-60, γ-radiation induced copolymerization of ethylene with tetrafluoroethylene was carried out in the gas phase and in the liquid phase by using five solvents (liquefied carbon dioxide, carbon tetrachloride, ethylchloride, chloropentafluoroethane, and 1,2-dichloro-tetrafluoroethane) at a dose rate of 25000 rad/hr under a pressure of 300 kg/cm2 at 30°C. A lower rate of the copolymerization and a copolymer of a lower molecular weight were obtained in liquid carbon dioxide and carbon tetrachloride than in the gas phase without a solvent. In ethyl chloride, the rate increased slightly, but the molecular weight decreased. On the other hand, both the rate and the molecular weight increased markedly in the fluorocarbon solvents. As a result of a detailed investigation of the copolymerization in 1,2-dichloro-tetrafluoroethane, a linear increase in the copolymerization rate and the copolymer molecular weight with the amount of solvent was noted, and there was no noticiable influence of the solvent on the copolymer composition. A kinetical discussion indicated that the addition reaction of tetrafluoroethylene to radicals produced by the influence of primary radiation on the reaction mixture is an important step in initiating the copolymerization. Also, the propagation reaction seemes to be strongly promoted by the fluorocarbon solvents.
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