Physico-chemical aspects of polyethylene processing in an open mixer. Part 12: Heterogeneous kinetics of hydroxyl group formation at low temperature

The heterogeneous oxidation model is adapted to polyethylene melts at low temperature. It takes into account that decomposition of associated hydroperoxides in the low temperature range is no longer fast in comparison with their formation through successive oxidation of the same elementary volumes. Consideration of both formation and decomposition of associated hydroperoxides leads to a mathematical model accounting for the experimental results. Accumulation of associated hydroperoxides as well as alcohol formation in the low temperature range are explained. The rate of decomposition that is deduced from data fitting is comparable to the published rate for low molecular mass associated hydroperoxides. Different aspects of heterogeneous oxidation kinetics are discussed.