Influence of light intensity on the photooxidation of polypropylene

Polypropylene was photooxidized under polychromatic light (lambda greater than or equal to 300 nm) at different intensities of the incident light. The variations of intensity were obtained without changing the relative spectral distribution of the source or the temperature at the surface of the exposed samples. Oxidation curves were generated by FTIR analysis of the exposed polypropylene films. The light intensity dependence of both the induction period and the steady-state rate of oxidation was plotted. Simple kinetic behaviours were determined, showing a variation of the steady state rate of oxidation with the square root of the light intensity and the variation of the induction period being directly proportional to the inverse of the light intensity. (C) 1997 Elsevier Science Limited.