Melt free-radical grafting of hindered phenol antioxidant onto polyethylene

A monomeric antioxidant (3) was prepared by reacting 3,5-di-tert-butyl-4-hydroxybenzyl alcohol (1) with N-[4-(chlorocarbonyl) phenyl] maleimide (2). This reactive antioxidant was grafted onto polyethylene (PE) by melt processing with free-radical initiators in a mini-max molder. The IR spectra of the grafted PE showed that the monomeric antioxidant was introduced onto the PE. IR spectroscopic methods and titration were used for the quantitative determination of the extent of grafting of the monomeric antioxidant. Also, the extent of crosslinking was indicated by the gel content. Grafting occurred in the following order: dicumyl peroxide (DCP) > benzoyl peroxide > 2,2′-azobisisobutyronitrile. The influences of the DCP concentration and monomeric antioxidant on the extent of grafting were studied. The effects of the reaction time and temperature were also determined.