BEHAVIOR OF ANTIOXIDANT IN POLYETHYLENE

In the reported experiments, the changes in the oxidative induction period of polyethylene and the concentration of antioxidant, 4,4 prime -thio-bis(3-methyl-6-t-butyl phenol), in polyethylene during thermal aging were investigated. The concentration decreased following a first-order kinetics. The induction period depended only on the antioxidant concentration and was independent of the aging conditions. The Arrhenius plot of the rate constants of the concentration decrease was linear above and below the polyethylene melting range, and an activation energy was obtained. The main factor in the concentration decrease was the evaporation of the antioxidant from the surface, and the evaporation rate constant of the antioxidant dissolved in polyethylene was obtained.