The thermal degradation of polyvinylchloride in solution. II. The kinetics of the crosslinking reaction

Abstract

AbstractThe cross‐linking of polyvinylchloride in ethyl benzoate solution was studied over the temperature range 178 to 212°C. in an atmosphere of nitrogen. The effects of variation in polymer concentration and in molecular weight of the polymer on the time taken for the polymer solution to gel were observed, and the rate of crosslinking was calculated from such data by applying Flory's theory of gelation. Over the above‐mentioned temperature range the expression for the rate of crossbond formation was found to be 2.0·103 e‐23,000/RT cw2 crossbonds/1.·sec., where cw is the polymer concentration in monomoles/1. This expression applies to polymer samples with number average degrees of polymerization varying from 192 to 905, and may well apply to an even wider range.The addition of free radical initiators and free radical inhibitors had little effect on the time of gelation whereas oxygen retarded or prevented gel formation. The results in general support the view that the crosslinking process proceeds by a non‐radical mechanism, and involves a random condensation reaction between two structural units in different polymer molecules with the elimination of HCl.