Abstract
The antagonism between nitroxides of hindered amine light stabilizers (HALS NO) and phenolic antioxidants, such as 2,6-di-t-butyl-4-methylphenol (BHT), was investigated. Identification of the reaction products of HALS NO and BHT clarified the formation of HALS hydroxylamine (HALS NOH) and HALS amine (HALS NH) by the reduction of HALS NO, and the formation of quinone methide and stilbene quinone by the oxidation of BHT. The identification of these products in the reaction of HALS NO with BHT suggests a new antagonism between HALS NO and BHT: two molecules of HALS NO form HALS nitrosonium by electron transfer. The nitrosonium has strong oxidation power, and uselessly oxidizes a phenol such as BHT to quinone methide and finally stilbene quinone, while the nitrosonium and HALS NO are reduced to HALS NOH and HALS NH.
