Nitroxide compounds hindered amine stabilizers

The second category is that of free radicals traps. For example, hindered amines are excellent light-stabilizing compounds their oxidation generates stable free radicals called nitroxide that are able to efficiently trap reactive free radicals. Very recently, such nitroxide radicals were used to prevent a... 

Attachment of B ansformation Products of Stabilizers. Up-to-date knowledge dealing with the chemistry of transformation products of phenolic [6, 15, 17, 20] and aromatic aminic [16, 43, 230] antioxidants and photoantioxidants based on hindered piperidines [10] indicates the possibility of attaching compounds having structures of quinone imine or quinone methide, or of radical species like cyclohexadienonyl, phenoxyl, aminyl or nitroxide to polymeric backbones. These reactions proceed mostly via reactivity of macroalkyl radicals derived fi-om stabilized polymers. Various compounds modelling this reactivity have been isolated [19, 230]. These results are of importance mainly for the explanation of mechanisms of antioxidant activity [6, 22, 24]. 

In Table III, the positive interaction between IMZ stearate (6) and the hydroxybenzoate stabilizer UV-Chek AM-340 is shown. This degree of lifetime enhancement was not achieved in any of the HALS compounds synthesized in which the hydroxybenzoate group was present as an intramolecular substituent. The proximity of the hindered phenolic group may in some way affect generation of the nitroxide radicals from the amine nitrogen. 

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