Studies on copolymers of vinyl chloride with diethyl fumarate,isobutylene and vinyl bromide as PVC models with chain irregularities—III The influence of the tacticity and of the copolymer composition on the thermal degradation: The influence of the tacticity and of the copolymer composition on the thermal degradation

The thermal degradation kinetics of pairs of vinyl chloride copolymers with diethyl fumarate, isobutylene and vinyl bromide, having the same composition but different tacticity, were followed by conductivity measurements. From the results for degradation up to 0·3% and up to 10%, it follows that syndiotactic sequences in PVC give rise to high degradation rates in agreement with results of previous work on homopolymers of vinyl chloride. On the basis of kinetic aspects as well as u.v.- visible spectra of degraded samples, the influence of tacticity on the thermal degradation of copolymers is discussed. This effect is compared to that of weak points introduced in the PVC chain by means of copolymerization.