Characterising in situ activation and degradation of hindered amine light stabilisers using liquid extraction surface analysis-mass spectrometry

Paine, M. R. L., Barker, P. J., & Blanksby, S. J. (2014) Characterising in situ activation and degradation of hindered amine light stabilisers using liquid extraction surface analysis-mass spectrometry. Analytica Chimica Acta, 808, pp. 190-198.

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Changes in the molecular structure of polymer antioxidants such as hindered amine light stabilisers (HALS) is central to their efficacy in retarding polymer degradation and therefore requires careful monitoring during their in-service lifetime. The HALS, bis-(1-octyloxy-2,2,6,6-tetramethyl-4-piperidinyl) sebacate (TIN123) and bis-(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate (TIN292), were formulated in different polymer systems and then exposed to various curing and ageing treatments to simulate in-service use. Samples of these coatings were then analysed directly using liquid extraction surface analysis (LESA) coupled with a triple quadrupole mass spectrometer. Analysis of TIN123 formulated in a cross-linked polyester revealed that the polymer matrix protected TIN123 from undergoing extensive thermal degradation that would normally occur at 292 degrees C, specifically, changes at the 1- and 4-positions of the piperidine groups. The effect of thermal versus photo-oxidative degradation was also compared for TIN292 formulated in polyacrylate films by monitoring the in situ conversion of N-CH3 substituted piperidines to N-H. The analysis confirmed that UV light was required for the conversion of N-CH3 moieties to N-H - a major pathway in the antioxidant protection of polymers - whereas this conversion was not observed with thermal degradation. The use of tandem mass spectrometric techniques, including precursor-ion scanning, is shown to be highly sensitive and specific for detecting molecular-level changes in HALS compounds and, when coupled with LESA, able to monitor these changes in situ with speed and reproducibility. (C) 2013 Elsevier B. V. All rights reserved.

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ID Code: 68921
Item Type: Journal Article
Refereed: Yes
Additional Information: ISI Document Delivery No.: 281TC
Times Cited: 1
Cited Reference Count: 31
Paine, Martin R. L. Barker, Philip J. Blanksby, Stephen J.
Australian Research Council (ARC) [LP0775032, LP110200322]; BlueScope Steel Limited; ARC Centre of Excellence For Free Radical Chemistry and Biotechnology [CE0561607]; Australian Postgraduate Award (Industry)
M.R.L.P. and S.J.B. acknowledge funding from the Australian Research Council (ARC) (LP0775032), (LP110200322), BlueScope Steel Limited, and support from the ARC Centre of Excellence For Free Radical Chemistry and Biotechnology (CE0561607). M. R. L. P. is the holder of an Australian Postgraduate Award (Industry).
Elsevier science bv
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Keywords: Hindered amine light stabiliser, Liquid extraction surface analysis, Ambient mass spectrometry, Polymers, Tandem mass spectrometry, Polymer, additives, automotive paint systems, uv-absorber addition, organic coatings, polymer stabilization, molecular-structure, mechanistic aspects, nitroxyl radicals, photostabilization, oxidation, hals, ARC
DOI: 10.1016/j.aca.2013.09.039
Subjects: Australian and New Zealand Standard Research Classification > CHEMICAL SCIENCE (030000)
Divisions: Current > QUT Faculties and Divisions > Science & Engineering Faculty
Copyright Owner: Elsevier
Deposited On: 20 Mar 2014 00:11
Last Modified: 17 Feb 2015 06:51

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