Colour and chemical changes on photodegraded beech wood with or without red heartwood

Abstract

The focus of this study was to investigate the chemical and colour changes occurring at different exposure times on artificially photo-irradiated surfaces of normal and red heartwood in beech in order to understand the mechanisms that cause the changes and to evaluate the possibility of usages of beech not only for energy production purposes. In this sense, surface colour modifications are of crucial importance to define the commercial value of beech wood. The artificial photo-irradiation of the wood samples was performed in a Solar Box, equipped with an ultraviolet filter that cuts off the spectrum at 280 nm. Reflectance spectrophotometry and Fourier transform infrared (FTIR) spectroscopy were used to assess artificial sunlight influence. The experimental data were statistically treated to evaluate their significance. Colour monitoring revealed that wood surface colour undergoes an important variation due to photo-irradiation, occurring within the first 24-48 h. Moreover, it was found that the chromatic coordinates (L*a*b*) in normal wood and in red heartwood tended to similar values after 504 h. FTIR spectroscopy allowed for investigating the rate of photodegradation of wood surface due to oxidation reactions of wood components. The results were validated by statistical analysis applied both to the colorimetric and spectroscopic data.

Chemical composition of lignocellulosic biomass in the wood of Abies religiosa across an altitudinal gradient

“…The first band is related to lignin carbonyls, while the second is assigned to lignin and hemicellulose [39,44]. Changes in these carbonyl bands from wood samples are related to chemical variations mainly from lignin, as reported in another studies [59,[62][63][64].…”

A new approach for the modelling of chestnut wood photo-degradation monitored by different spectroscopic techniques

“…FT-IR spectroscopy, applied at the same samples and irradiation times, allowed investigating the rate of photo-degradation of wood surface due to oxidation processes of wood components (Calienno et Photo-degradation of wood components, particularly lignin, produces new nonconjugated/conjugated carbonyl group that causes the increase of the carbonyl band at 1740 cm −1 (5747 nm) and the decrease of the lignin band at 1507 cm −1 (6636 nm) (Calienno et al 2014;Müller et al 2003;Popescu et al 2011;Wang and Ren 2008). On the other hand, the intensity of the band of carbohydrates at 1377 cm −1 (7262 nm) is not significantly affected by irradiation, so it can be used as an internal reference to calculate the band ratios (Pandey 2005;Agresti et al 2013;Popescu et al 2011).…”

Effects of Air Relative Humidity and Temperature on Photodegradation Processes in Beech and Spruce Wood

“…The energy of UV photons is enough to split the chemical linkages of wood. Different investigations have found that the deterioration is primarily related to the decomposition of lignin (Hon and Minemura 2001;Bekhta and Niemz 2003;George et al 2005;Pandey 2005a;Sharratt et al 2009;Popescu et al 2011;Teacǎ et al 2013;Calienno et al 2014;Bonifazi et al 2015). Free phenoxyl radicals are created during lignin degradation, and these further react with oxygen to produce carbonyl chromophoric groups (Tolvaj and Faix 1995;Colom et al 2003;Xie et al 2005;Gou and Guan 2010;Rosu et al 2010).…”