Radiolytic degradation of poly(vinyl chloride) systems

We examined the gamma radiation effects on PVC plasticized with di(2-ethylhexyl)phthalate (DEHP), diisobutyl phthalate, trioctyl trimellitate and Viernol(R), as well as its effect on PVC plasticized with DEHP and stabilized with Tinuvin P. The PVC samples were analysed, before and after irradiation at different doses, by UV spectroscopy, viscometry and mechanical testing. A multivariate statistical analysis was carried out on five properties: tensile strength, percent elongation, number of scissions per chain, viscosity-average molecular weight and UV-visible absorbance. The scores from a principal component analysis (PCA) of the nonstabilized samples show that the PVC/DEHP samples were the most degraded by chain scission upon irradiation, especially at the 25 and 60 kGy dosages, while the 400 nm absorbance, associated with film yellowing, remained relatively unchanged for these samples. For the other three systems, degradation by chain scission is smaller, and the UV absorbance is more dependent on radiation dosage. For the PVC/DEHP samples, the addition of Tinuvin P significantly decreases the number of scissions per chain, especially at 25 and 60 kGy irradiation doses. (C) 2004 Elsevier Ltd. All rights reserved.