γ‐Ray‐induced copolymerization of ethylene and vinyl chloride in liquid carbon dioxide

Abstract

AbstractThe γ‐ray‐induced copolymerization of ethylene and vinyl chloride with the use of liquid carbon dioxide as a solvent was studied under a total pressure of 400 kg/cm2, with a dose rate of 2.5 × 104 rad/hr at 30°C. A rubberlike, sticky polymer is obtained when the molar concentration of vinyl chloride is less than 30% in the monomer mixture, and the polymer is a white powder at higher concentrations of vinyl chloride. Infrared, x‐ray, and differential thermal analyses confirm that the polymerization products are noncrystalline, true random copolymers. The rate of copolymerization decreases markedly when a small amount of vinyl chloride is added to ethylene monomer. In the range of vinyl chloride concentration higher than 5%, however, the rate and the molecular weight of copolymer increase with increasing concentration of vinyl chloride. It has been concluded from kinetic considerations based on these results that the rate of initiation increases proportionally with the concentration of vinyl chloride. Further, the growing chain radicals are shown to be deactivated by the cross‐termination reaction between the radicals with terminal unit of ethylene and vinyl chloride, and no transfer reaction occurs.