Chlorine dioxide resistance of different phenolic antioxidants in polyethylene

A series of polyethylene tape samples containing 8 different phenolic antioxidants (concentration = 0.1 ± 0.01 wt.%) were exposed to water containing 10 ppm chlorine dioxide buffered to pH = 6.8 at 70 °C for different periods of time. The degradation rate and depletion time of the antioxidants in the polyethylene were obtained by oxidation induction time measurements using DSC. The majority of the tape samples (6 out of 8) showed a simple behaviour: the rate of antioxidant loss decreased and the antioxidant depletion time increased in linear fashion with increasing initial molar concentration of phenolic groups in the polymer. The tape that contained Hostanox O3 had a high initial phenolic concentration but it exhibited a short antioxidant depletion time due to the limited solubility of this antioxidant in polyethylene. Tapes containing Irganox 1330 and Cyanox 1790 showed antioxidant depletion times that were almost twice that of the other antioxidants with the same initial molar concentration of phenolic groups.