Antioxidative properties of phenyl-substituted phenols. Part I. The mechanism of synergism between 4-alkoxy-2,6-diphenylphenols and ββ′disubstituted diethyl sulphides

A pronounced synergism between 4-alkoxy-2,6-diphenylphenols and ββ′disubstituted diethyl sulphides has been observed in the inhibition of autoxidation of polypropene at 180 °C. The mechanism of this synergistic action (at temperatures 150 °C) has been investigated. N.m.r. model experiments have shown that the phenolic antioxidant (AH) is regenerated continuously from the phenoxyl radical (A·) by hydrogen atom donation by the sulphenic acid, a product originating from the ββ-′disubstituted diethyl sulphide. This observation is of possible contributory importance to the understanding of the mechanism of synergistic effects.