Quenching of singlet oxygen by hindered amine light stabilisers. A flash photolytic study |
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| Authors: | R Ballardini G Beggiato P Bortolus A Faucitano A Buttafava F Gratani |
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| Institution: | Centro di Studi per la Fotochimica e la Reattività degli Stati Eccitati dei Composti di Coordinazione del C.N.R., 44100 Ferrara, Italy;Istituo di Fotochimica e Radiazioni di Alta Energia del C.N.R., Via de'' Castagnoli 1, 40126 Bologna, Italy;Istituto di Chimica Generale, Università di Pavia, Via Teramelli 12, 27100 Pavia, Italy;Montefluos C.R.S., Via Bonfadini 148, 20100 Milano, Italy |
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| Abstract: | Rate constants for the quenching of singlet oxygen (1O2, 1δg) for a series of piperidines, piperidine-N-oxyl free radicals and some commercially used hindered amine light stabilisers (HALS) have been measured by a laser flash photolysis method. Quenching rate constants are in the order: piperidine-N-oxyl free radicals ≤ secondary piperidines < tertiary piperidines. For some commercial HALS, 1O2 quenching rate constants and the light protective effect towards polypropylene photo-oxidation have been compared. No correlation has been found between the stabilizing action and the quenching efficiency towards 1O2. The data obtained point to little contribution of singlet oxygen to the key steps of polyolefin photo-oxidation. |
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