Influence of inorganic salts mixture and a commercial additive on the degradation of poly(vinyl chloride)

Samples of commercial poly(vinyl chloride) (PVC) containing a Hindered Amine Stabilizer (HAS) and samples containing a salt mixture of CuCl2/KI both in 0.1, 0.3, 0.5 and 0.7wt% concentration of HAS or salt mixture were investigated. The samples were irradiated with gamma radiation (60Co) at room temperature in air at 25 kGy, sterilization dose of PVC medical supplies. The viscosity-average molecular weight (Mv) was analyzed by viscosity technique. Comparison of viscosity results obtained before and after irradiation ( at 25 kGy) of PVC showed crosslinking effect is predominant. On the other hand the PVC-HAS systems and PVC-salt systems showed a decrease in Mv values on irradiated samples reflecting the main chain random scissions effect. However the PVC-salt at 0.5wt% concentration showed no significant degradation index value. This result suggests that salt keeps the good radiolytic stabilization behavior of gamma-irradiated PVC and the HAS additive is not efficient on radiolytic stabilization of PVC. The CuCl2/KI mixture at 0.5wt% in the PVC matrix influenced the thermal behavior of the polymer increasing of 42 deg C in maximum thermal degradation temperature. In addition, the salt mixture influences significantly the Young's Modulus of PVC increasing the rigidity of polymer. (author)