Polymer degradation within the glass transition range

Polymer degradation around the glass transition temperature exhibits frequently an anomalous behaviour. Starting from the hypothesis that such anomalies are related to the glass transition phenomenon, the most relevant data reported in the literature are reviewed and a theoretical description, based on the free volume approximation is suggested. The degradation process is split in three steps. It is proved that the dominant contributions come from the defect's diffusion step and from the proper chemical stage, which may be supposed to be statistically independent. It is explain, using an extended WLF equation why these anomalies are not located exactly at the glass transition temperature. The agreement between theory and experimental data reported elsewhere is good.