Mechanisms of antioxidant action: Effect of processing on the transformation products of thiophosphoryl compounds in polyolefins

It is shown that low density polyethylene or polypropylene processed in the presence of thiophosphoryl disulphides or thiocarbamoyl disulphides in air or in the presence of hydroperoxides are much more photo-stable than analogous samples processed normally. This is found to be true when the additives are added at normal (low) concentration levels or as concentrates which are subsequently diluted in the polymer to normal levels. Among the products formed when bis dialkyl dithiophosphoryl disulphides are oxidatively processed in polyethylene are polymer-bound thiophosphoryl compounds which are believed to generate sulphur acids slowly in the polymer.