Kinetics of the stabilizing effect of calcium and zinc stearates in the thermal degradation of PVC: Part II

Abstract The formation of ester groups during the thermal degradation of PVC sheets stabilized with mixtures of calcium stearate and zinc stearate was recorded by infra-red spectroscopic measurements. The kinetic analysis of these data showed that the formation of ester groups is an ionic reaction controlled by the ionic strength of the samples according to the Debye-Huckel theory. The complexation of the two stearates during the heating of the PVC sheets reduces the ionic strength and increases thereby the rate of ester formation. Rate equations based on this concept were derived and used conveniently for modelling the formation of ester groups and stearic acid as well as the consumption of stabilizers during the thermal degradation.