ASSESSMENT OF CHROMOPHORES IN CHEMICALLY TREATED AND AGED WOOD BY UV-VIS DIFFUSE REFLECTANCE SPECTROSCOPY
authors Tribulova, T; Kacik, F; Evtuguin, D; Cabalova, I
nationality International
journal CELLULOSE CHEMISTRY AND TECHNOLOGY
author keywords accelerated ageing; chemically treated wood; chromophores; diffuse reflectance spectroscopy; inorganic salts
keywords LIGHT-ABSORBING PROPERTIES; RAMAN-SPECTROSCOPY; PHENOLIC-COMPOUNDS; PULP COMPONENTS; COLOR; LIGNIN; PAPER; ABSORPTION; MECHANISM; HEAT
abstract The optical properties and degradation of fir wood treated by different inorganic salts, which are components of waterborne wood preservatives, were studied before and after wet-thermal accelerated ageing (T=85 degrees C, RH=65%, for 30 days) using UV-Vis diffuse reflectance spectroscopy. The colour of all impregnated samples was due to the same chromophoric structures, thus revealing that the primary reactions leading to colour changes are essentially very similar. These chemically treated as well as standard (non-treated, unaged) and reference (treated only with distilled water, unaged/aged) samples have a significant absorption band at 358 nm, along with a shoulder near 265 nm of various intensity. The broad band at higher wavelength is attributed to the chromophoric structures derived especially from lignin, i.e. quinones, stilbenes, charge transfer complexes causing a bathochromic shift and other conjugated carbonyl structures. Coniferaldehyde is also a major contributor to this absorption. The band at 265 nm belongs to chromophores arising predominantly from carbohydrate degradation products, i.e. furan derivatives, quinone-type derivatives, catechol structures. Catechol structures (colourless) form coloured complexes with transition metal cations (Cu2+, Fe3+) or are oxidized to form highly coloured benzoquinone structures. Alkaline solutions of borax cause the reduction of conjugated and non-conjugated carbonyls and the degradation of coniferaldehyde. Generally, after ageing, the samples show higher absorptions in the visible region of the spectra in comparison. with the unaged ones, which explains their yellowing and loss of brightness after the action of elevated temperature and moisture.
publisher EDITURA ACAD ROMANE
issn 0576-9787
year published 2016
volume 50
issue 05-Jun
beginning page 659
ending page 667
web of science category Materials Science, Paper & Wood
subject category Materials Science
unique article identifier WOS:000386993700018
link http://www.cellulosechemtechnol.ro/pdf/CCT5-6(2016)/p.659-667.pdf
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