Relation between thermal degradation and tacticity of PVC

Abstract

Abstract The thermal degradation up to 0.3% at 180°C of sets of PVC prepared in such a way that samples have different tacticity has been studied by conductimetric methods. The degradation rates of PVC were found to depend on the syndiotacticity content; the plots of degradation rates as function of a tacticity parameter show a minimum at which the corresponding polymers are very stable. The kinetic results as well as the shape of UV‐visible spectra of degraded polymers suggest an influence of tactic sequences on propagation step. The degradation of vinyl chloride copolymers with diethyl fumarate, isobutylene, and vinyl bromide, having the same composition but very different tacticity in PVC sequences, was also studied under the same conditions. For each pair of copolymers, the higher degradation rate was always that of the sample having more syndiotactic sequences.