THERMAL AND PHOTOOXIDATION OF POLYPROPYLENE INFLUENCE OF LONG-TERM AMBIENT OXIDATION - SPECTROSCOPIC, THERMAL AND LIGHT-SCATTERING-STUDIES

The influence of long-term ambient storage conditions in the presence of air has been examined on the thermal and photooxidation of unstabil ized polypropylene. Samples of polypropylene have been aged under ambi ent storage for 12 years together with a control sample kept under ref rigeration at -20 degrees C. The samples have been examined using seco nd order-derivative absorption, fluorescence and phosphorescence spect roscopic techniques, thermal analysis (d.s.c.), light scattering and h ydroperoxide analysis. All the polymer samples stored under ambient co nditions exhibit significant increases in luminescent species and hydr operoxide concentrations as a consequence of slow oxidation processes. The d.s.c. and light scattering analysis show that these polymers exh ibit an increase in crystallinity compared with that which has been st ored by refrigeration. The data are related to the thermal and photoox idative behaviour of the polymers using Fourier transform infra-red sp ectroscopy (FTi.r.) and compared with that of a modern suspension grad e polypropylene. (C) 1996 Elsevier Science Ltd.