Effect of sample size and environment on the thermal degradation of polymers

A model that takes into account mass transfer resistances at the polymer-melt and at the melt-carrier gas interfaces during the course of thermal degradation of relatively ‘large’ samples of polymer, is proposed. It is tested against experimental weight loss data for polypropylene, in the temperature range 390–430°C, obtained from the pyrolysis of 0·1–5 g samples. The weight loss data do not follow first-order kinetics and depend on the sample size. It is found that the model is capable of predicting the experimental observations.