Aromatic Secondary Amines as Antioxidants for Polyolefins. Part 1. 9,10-Dihydroacridine (Acridan) Derivatives

Abstract: A series of five acridan derivatives was studied as antioxidants in the thermoxidation of polypropylene. None induced major retardation in the polymer oxidation. Two of them, 9,9-diphenyl- and 9,9-dimethyl-acridans, showed synergism when used in the presence of dilauryl thiodipropionate (DLTP). In order to understand the role of the intermediate nitroxides during the oxidation, 9,9-diphenylacridan-1-oxyl was prepared and studied in the presence and in the absence of DLTP. The main reactivity of the nitroxide is explained through disproportionation and hydrogen abstraction reactions and formation of alkylated hydroxylamine, where the alkyl group is the polymer chain

SPIN LABELLING OF DEGRADED POLYPROPYLENE. PART 1. FORMATION OF OXAZOLIDINE NITROXIDE

Abstract: The kinetics of nitroxide formation on a polypropylene (PP) chain by reaction between carbonyl groups of gamma-irradiated PP and 2-amino-2-methyl-1-propanol has been studied, During the reaction the total concentration of carbonyl and amine groups passes through a maximum. At the end of the reaction a weak ESR signal due to nitroxide groups was detected and its intensity was strongly enhanced by peroxidation with m-chloroperbenzoic acid. The presence of nitroxides after the reaction with the aminoalcohol has been explained by the interaction of an oxazolidine moiety with singlet oxygen coming from the decomposition of PP-hydroperoxides or by reaction of the latter compounds with the oxazolidine nucleus