Stabilization of nontoxic PVC formulation for gamma irradiation sterilization, II. Effect of antioxidants

In order to investigate the fundamental data for the resistance of gamma radiation sterilization of polyvinylchloride (PVC), the formulations of the antioxidants such as commercial Irganox series and inorganic, processing aids, stabilizer aids, trans-stilbene oxide (StO) and so on have been carried out. The control and irradiated PVC samples with 1.5, 2.5 and 4.0 Mrad were characterized by mechanical tester, colorimetry, and extractant in water. Irganox 1010 was more effective than Irganox 1076 for color changes whereas Irganox 1076 was more effective than Irganox 1010 for the change of extractant. It was also observed the significant diminution of color changes for inorganic antioxidants as CaO and ZnO. Oxidized paraffin wax as lubricant, styrene-methylmetacrylate copolymers as processing aids, and nontoxic debenzoylmethane as secondary stabilizer did not show good stabilization for the irradiation. The new proposed radiation stabilizer in this study, StO, showed the significant improvement of gamma radiation resistance for the plasticized PVC. The possible mechanism could be explained that an epoxy functional group stabilizes effectively the processes of dehydrogenation, the formation of hydroperoxides, and the formation of oxygen containing groups, and the synergetic effects of an epoxy compound are more notable for the prevention of radiation oxidation in the presence of an aromatic group.