A Kinetic Study of the γ-Radiation-Induced Polymerization of Ethylene at a Normal Temperature

Abstract

Abstract The gamma-radiation-induced polymerization of ethylene was carried out in the intermediate pressure region from 70 to 400 kg./cm2 with a dose-rate from 5×103 to 4.3×105 rad./hr. and at a temperature of 30°C. An overall G-value of the 104 order was usually obtained. No induction period for polymerization was observed. The polymerization rate and the molecular weight of the polymer formed were shown to increase almost proportionally with the reaction time and with the pressure of ethylene. The dose-rate exponents of the rate and the molecular weight were found to be 0.9 and 0 respectively. These results indicate that the stationary-state hypothesis, i. e., that the rate of initiation is equal to that of termination, is not realized in this polymerization. From the kinetic discussion of the initial stage of polymerization, where the concentration of monomer remains essentially constant, it was concluded that the rates of termination and transfer reaction are very small; the life of polymer radicals is, therefore, quite long and the growing of polymer radicals proceeds successively under irradiation.