The Behaviour of Substituted Diaryl Nitroxyl Radicals and their Derivatives as Antifatigue Agents for Rubbers

Abstract

A variety of arylnitroxyl radicals and their precursors have been evaluated as antifatigue agents, antioxidants and antiozonants in natural rubber. Nitroxyl radicals and their derived hydroxyl amines were shown to be the active species during fatiguing and mechanistic studies using ESR have shown that these stable nitroxyl radicals are regenerated in a cyclicalmechanism, N-nitroso diaryl amines were shown to be highly effective antifatigue agents due in part to the formation and regeneration of the diaryl nitroxyl radicals. Diaryl nitrones were also shown to produce the corresponding nitroxyl radical during processing, although their antifatigue activity was low. However inclusion of a semi-hindered phenolic moiety in the molecule markedly improved activity...