Antioxidative Properties of Phenyl-Substituted Phenols

Phenyl-substituted phenols and sulfides show remarkable antioxidant synergism in polypropylene at 180°C., i.e., close to processing conditions. In our investigations into phenyl-substituted phenols we synthesized potential end-use antioxidants of this type. Oven-aging at 80°, 120° and 140°C was carried out with polyproylene films. The decay of the phenyl-substituted phenolic antioxidants was measured during the induction period using UV spectrophotometry to predict the time to embrittlement. In contrast to other chain-breaking antioxidants, the concentration of the phenyl-substituted phenolic antioxidant remained constant even after severe processing. These observations agree with the results of model compounds in polypropylene, which show that the phenyl-substituted phenol is regenerated continuously at higher temperatures (150°-200°C) by the sulfide or oxidation products of the sulfide.