Chemiluminescence from oxidation of polypropylene: Correlation with peroxide concentration

The chemiluminescence (CL) on heating in an inert atmosphere has been measured for samples taken at various times during oxidation of polypropylene (PP). Proportional relationships were obtained when the integrated emission (TLI) was plotted against peroxide concentration for all studied sets of parameters. Changes in melting temperature and molecular weight with ageing time were found to correlate with changes in the TLI. Oxidised PP was exposed to dimethylsulfide (DMS) for different periods with subsequent measurements of the CL and the peroxide concentration. The peroxide concentration has earlier been found to exhibit a two-step decay with DMS exposure time, indicating two fractions of peroxides with different reactivity. The CL was found to follow the same two-step decay, indicating that both peroxide fractions contribute to CL. The oxidative stability of PP, measured by CL induction times in oxygen, increases when the polymer is exposed to DMS. (C) 1996 Elsevier Science Limited