Thermooxidative degradation of polyolefins in the solid state—6. Kinetics of thermal oxidation of polypropylene

Abstract

Thermal oxidation of polypropylene films at 80°C was examined as a function of aging time, sample thickness, polymer grade and sample preparation. The experimental kinetics of functional group formation do not correspond to clear power laws as claimed in the literature. After the end of the induction period, the kinetics conform rather to an autoaccelerated, exponential-type increase in the early stages of oxidation. This is followed by a linear increase of the concentration of carbonyl groups in more advanced stages of oxidation. It is found that formal homogeneous kinetics accounts for some aspects of the experimental results with PP.