STUDIES ON THE WEATHERING PROCESS IN POLY(VINYL CHLORIDE) BY LASER-INDUCED FLUORESCENCE SPECTROSCOPY

Excimer laser induced fluorescence spectra of plasticised commercial poly(vinyl chloride) show two distinct regions of emission bands. The one in the ultraviolet region around 360 nm and the other in the visible around 450 nm are attributed to the emission from the plasticiser (dioctyl phthalate) and the carbonyl impurities, respectively. Artificial weathering is found to quench the fluorescence from the phthalates indicating a depletion of these chromophores through photo-oxidative reactions. A corresponding increase in the visible fluorescence suggests an increase in the concentration of carbonyl groups during the initial stages of weathering (up to 200 h of exposure in a Xenotest Weather-Ometer). Prolonged weathering (>200 h) depletes the primary chromophores and the fluorescence is then governed by the conjugated polyene generated through progressive photo-reactions. The phthalates and the carbonyl units constitute natural probes for the study of the photo-oxidative processes in commercial PVC. © 1989.