Mechanisms of antioxidant action: The behaviour of a bound antioxidant as an antiozonant

A rubber reactive antioxidant, 4-(mercapto acetamido)diphenylamine (I, MADA) was found to be more effective as an antiozonant when prereacted with the rubber chain (MADA-B) than when present as a conventional compounding ingredient (MADA-A) at the same molar concentration. In bound form after extraction MADA-B is as effective as an unextracted commercial antiozonant, iso-propylaminodiphenylamine (IPPD), at the same molar concentration. This result casts some doubt on the currently accepted view that antiozonants must migrate to the surface of the rubber in order to exert their protective effect.