Inhibition of the anthraquinone photosensitised oxidation of polypropylene by a hindered piperidine stabiliser: A spectroscopic study |
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Authors: | Norman S Allen |
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Institution: | Department of Chemistry, John Dalton Faculty of Technology, Manchester Polytechnic, Chester Street, Manchester M1 5GD, Great Britain |
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Abstract: | A hindered piperidine stabiliser, bis{2,2,6,6-tetramethyl-4-piperidinyl}-sebacate, has been found to inhibit the photo-sensitising effect of anthraquinone in polypropylene. On flash photolysis in n-hexane solution transient formation due to the semi-quinone radical (AH·) at 370 nm and subsequent formation of the hydroquinone (9,10-dihydroxyanthracene (AH2) were found to be effectively inhibited by the corresponding nitroxyl radical but not by the amine. The absence of the hydroquinone photoproduct was confirmed using fluorescence spectroscopy. With the aid of phosphorescence spectroscopy it is concluded that the nitroxyl radical is the effective stabilising species and operates by a radical scavenging mechanism to form the hydroxylamine, and not by excited state quenching. |
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