Thermal degradation of PVC synthesized with a titanocene catalyst II. Complementary isothermal results

The use of an isothermal degradation method on metallocene produced PVC and commercial PVC, under nitrogen and air atmospheres, reveals more details about degradation routes. Without regard to the polymer origin, the hydrochloric acid release occurs in two steps, which are reflected in molecular weight only under a nitrogen atmosphere; otherwise, the oxygen appears to be included in the scission/crosslinking process. On the one hand, Met PVC has unsaturations from its synthesis, producing a faster HCl release compared to Com PVC; consequently, its degradation resistance is lower. On the other hand, Com PVC has more oxidized species and has a natural tendency to include more of them. Surface area seems to have an important effect and is directly related to the rate of hydrochloric acid release. The latter is not supported by the chain oxidation mechanism, making the effect of the applied atmosphere more critical to the results obtained from the degradation experiments.