A Kinetic Study of the Free-Radical Bulk Polymerization of Ethylene

Abstract

Abstract The bulk polymerization of ethylene was carried out under mild conditions, i. e. pressures of from 183 to 400 kg/cm2 and temperatures of from 30 to 140°C, using azobisisobutyronitrile as an initiator. In polymerization at the low temperature of 40°C, both the polymerization rate and the molecular weight of the polymer formed increased with the reaction time. At the above temperature, the polymerization rate was shown to be proportional to the amount of initiator, and the molecular weight was found to be independent of it. Furthermore, both the polymerization rate and molecular weight were found to be proportional to the 2.5th power of ethylene fugacity. The dependencies of the polymerization rate and the molecular weight on the reaction time decrease with the rise in reaction temperatures from 30 to 100°C. A kinetical discussion indicated that the rate of termination is almost zero at 30–40°C, but that it increases with the temperature. The polymerization rate and the molecular weight were shown to be proportional to the 0.8 and 0.2th powers of the amount of the initiator. The activation energy of the initiation reaction was evaluated to be ca. 27 kcal/mol.