Antioxidants

Antioxidants can be classified by the way in which they interfere with the process of autoxidation. Two main types can be identified; the chain-breaking antioxidants which either reduce the alkylperoxyl radical or oxidise the alkyl radical and the preventive antioxidants which either retard the breakdown of hydroperoxides (metal deactivators, UV absorbers) or destroy them by non-radical mechanisms. Synergism results from the complementary action of antioxidants when used together. Recent studies of antioxidant mechanisms have led to the discovery of “stable” redox systems which are able to catalytically scavenge alkyl and alkylperoxyl radicals in competition with the normal reactions of these species in autoxidation. The physical behaviour (solubility, volatility etc.) of antioxidants can dominate their behaviour under certain conditions and the development of polymer-bound antioxidants is believed to be a solution to antioxidant migration and loss.