Oxidation of ultra high molecular weight polyethylene (UHMWPE) part 3: Decomposition of hydroperoxides with SO2 and its effect on the chemiluminescence signal

Samples of slightly oxidised UHMWPE were treated with SO2 to decompose hydroperoxides prior to chemiluminescence measurements. It was found that the effect was quite substantial, but it was not just due to the elimination of hydroperoxides; a stabilising effect was also manifested. This effect increased with an increasing concentration of hydroperoxides in the samples. The stabilising effect could not be seen in fresh samples or when the hydroperoxides were decomposed by heating the sample in nitrogen. In addition, a stabilising effect was also observed for samples in which the hydroperoxides were reduced by DMS. It was concluded that the stabilisation was due to the formation of H2SO4 in the case of SO2 and DMSO in the case of DMS. Both these substances can act as stabilisers against oxidative degradation of polymers and were evenly distributed in the sample films after the reaction with the hydroperoxides.