Physico-chemical aspects of polyethylene processing in an open mixer. Part 15: Product yields on bimolecular hydroperoxide decomposition

Abstract

The product yields are important characteristics of the various hydroperoxide decomposition reactions. The true bimolecular hydroperoxide decomposition is thought to be the dominant reaction in the early stages of polyethylene processing. The reaction probabilities and theoretical yields calculated for the reaction account for the ratio of alcohols to ketones in these early stages. The calculations yield a rate constant for the disproportionation between the alkoxy and peroxy radical that is of the same order as published data for corresponding very low molecular mass radicals. The other reactions of the caged radical pairs are the same as those discussed for the reaction between a hydroperoxide and an alcohol group. They easily account for the experimental data. Pseudo-monomolecular hydroperoxide decomposition involving a hydroperoxide group and a segment of the polymer requires only parameters already envisaged previously. It does not seem to be important for polyethylene processing. However, it has been envisaged for thermolysis of polyethylene hydroperoxides in a press. The product yields calculated in this work for this reaction do not agree with the data from thermolysis of polyethylene hydroperoxides. The calculations allow concluding that pseudo-monomolecular hydroperoxide decomposition cannot be the only reaction on thermolysis of polyethylene hydroperoxides.