Some aspects of a new class of sulfur containing phenolic antioxidants

• Published in: Polymer degradation and stability 1995, Vol.49 (1), p.1-9
• Main Authors: Meier, Hansrudolf, Dubs, Paul, Künzi, Hanspeter, Martin, Roger, Knobloch, Gerrit, Bertterman, Hans, Thuet, Benoît, Borer, Armand, Kolczak, Urszula, Rist, Günther
• Format: Article
• Language: English
• Subjects: Applied sciences; Compounding ingredients; Exact sciences and technology; Polymer industry, paints, wood; Stabilizers (antioxydants, antiozonants, etc.); Technology of polymers
• ISSN: 0141-3910; 1873-2321
• DOI: 10.1016/0141-3910(95)00058-T

The commercial sulfur containing antioxidant AO2 (Irganox 1520) is compared with other classical phenolic antioxidants, and its special autosynergistic profile, particularly under dynamic test conditions (Brabender, 160 °C), in commercial polybutadiene rubber is investigated. AO2 outperforms all other tested phenolic stabilizers. A tentative mechanistic explanation for the action of AO2 is given, consisting of either a concerted reaction or a ‘tandem reaction’ of the antioxidant with macroalkylperoxy radicals. Other mechanistic pathways, for instance the role of the phenoxy radical 8 or its C,Orecombination products with oxygen centered radicals (such as macroalkylperoxy radicals) and of the recently synthesized stable quinone methide 10 are discussed. CIDNP experiments, generating the radical 8 from AO2, demonstrate that the main reaction between phenoxy radicals 8 is regioselective C,O-recombination, giving rise to the dimers 9a and 9b and no direct formation of quinone methide 10 and C,C-coupling products is observed.