The efficiency of 2-(2-hydroxyphenyl)imidazole derivatives as copper deactivators in radiation crosslinked low density polyethylene

Abstract 2-(2-Hydroxyphenyl)imidazoles have proved to be effective copper deactivators in crosslinked low density polyethylene (XLDPE). The induction time of the oxidation of XLDPE/Cu/XLDPE sandwiches determined by the oxygen uptake in air and in oxygen at 165°C and in some cases at 180°C has been used to characterize the copper deactivating effect. The chemical structure of 2-(2-hydroxyphenyl)imidazole and above all -benzimidazole had been varied by substitution, and the oxygen induction time was determined as a function of this structure. The substitution of a labile hydrogen with an alkyl group largely removes the copper deactivation. On the other hand a nitro group, increasing the acidity of the phenolic OH group, causes the most effective copper deactivation in XLDPE.