The thermal degradation of polyvinylchloride in solution—III. The effect of solvent on the kinetics of dehydrochlorination

Abstract

The dehydrochlorination of polyvinylchloride in solution has been studied over the temperature range 178–243° in an atmosphere of nitrogen. Benzophenone, tritoluylphosphate, ethylbenzoate, dioctylphthalate, dichloronaphthalene and benzyl alcohol were used as solvents. The reaction was fast in benzophenone and tritoluylphosphate, moderate in ethylbenzoate, dioctylphthalate, and dichloronaphthalene, and slow in benzyl alcohol. The apparent energy of activation varied from 22 to 30 kcal/mole. It was in the region of 30 for benzophenone and tritoluylphosphate, and from 22 to 26 kcal/mole for the remaining solvents. The rate depends upon the first power of the polymer concentration, but slight deviations occur at high concentrations and at the higher temperatures. The effect of degree of polymerization on the rate was studied using fractionated polymer. No systematic dependence was observed. The results have been discussed and explanations of the effects of solvents on the thermal degradation of polyvinylchloride have been put forward.