The autoacceleration of polypropylene thermo-oxidation in reduced coordinates: effect of the oxidation temperature and of polyolefin structure

Polypropylene samples ranging from highly isotactic (100% by FTIR) to fairly isotactic (76.6% by FTIR) have been thermo-oxidised in the temperature interval 80–150°C and the chemiluminescence emission along the induction and autoacceleration stages has been recorded. Of these oxidation curves, some of them are superimposable when comparing them after normalisation to their respective inflection points, what we have called representation in reduced co-ordinates. For example, the auto-acceleration curves in reduced coordinates corresponding to the oxidation of the more isotactic samples at high temperature are extremely similar to curves corresponding to the less isotactic samples at low temperatures. This is interpreted as being due to the similarity in nature of the polymer fraction, which is actually oxidised at each temperature.