Colour Stability of Thermally Modified Wood during Short-Term Photodegradation

Abstract

Dry thermal treatments of wood samples were carried out at 160 and 200 °C. After each treatment, the samples were irradiated using a strong UV emitter mercury lamp, and the colour change was then evaluated. For control, untreated samples were also irradiated using the same mercury lamp. Results showed that the extractive content of the wood played an important role in the colour change not only during thermal treatment but also during light irradiation. It was found that, compared to the thermally untreated samples, the thermal treatment at 200 °C reduced the red colour change due to photodegradation. The yellow colour change of photodegradation was hardly affected by the applied thermal treatments, showing that thermal treatments were not able to reduce the light degradation of lignin. The applied treatments slightly stabilized the wood against the degrading effect of light. The wood treated at lower temperature (160 °C) had less colour change induced by the light source.

Colour stability of oil-heat treated black locust and poplar wood during short-term UV radiation

“…The dry thermal treatment generated twice the diversity in lightness than OHT (Fig. 2), applying the same temperature and time conditions [25]. The reason is that oil-heat treatment prevents the oxidation.…”

“…The colour stability of OHT samples was compared to the results of dry heat-treated samples published in Tolvaj et al [25]. Some of these data are presented in this paper as well.…”

“…Tolvaj et al [25] monitored the short-therm photodegradation properties of black locust, poplar, spruce and larch samples pretreated at 160 and 200 C for 2, 4 and 6 h. The short term UV irradiation was carried out for up to 36 h. "Results showed that the extractive content of the wood played an important role in the colour change not only during thermal treatment but also during light irradiation. It was found that, compared to the thermally untreated samples; the thermal treatment at 200 C reduced the red colour change caused by photodegradation.…”

Color and FTIR Analysis of Chemical Changes in Beech Wood (Fagus sylvatica L.) after Light Steaming and Heat Treatment in Two Different Environments

“…More advanced color and related chemical structural changes (e.g., Tdjeersma and Militz 2005;Hill 2006;Windeisen et al 2007;Niemz et al 2010;Esteves et al 2013;Yildiz et al 2013;Tolvaj et al 2014;Fabiyi and Ogunleye 2015;Cheng et al 2016) occur by heat treatment of wood at high temperatures (180 to 240 °C) in controlled inert atmosphere, steam, vacuum, fumes with low/no content of oxygen to avoid burning. Chemical changes following exposure of wood (including beech) to elevated temperatures have been extensively studied (e.g., Militz 2002;Tdjeersma and Militz 2005;Windeisen et al 2007;Esteves et al 2013;Yildiz et al 2013;Tolvaj et al 2014;Fabiyi and Ogunleye 2015;Cheng et al 2016).…”

Effects of Ageing on the Color and Surface Chemistry of Paulownia Wood (P. elongata) from Fast Growing Crops

“…Infrared spectra are sensitive indicators of chemical changes, especially light-induced natural and accelerated ageing (Colom et al 2003;Pandey 2005;Pandey and Vuorinen 2008;Chang et al 2010a,b;Roşu et al 2010;Tolvaj et al 2013). Moreover, chemical changes in thermally treated wood revealed by FTIR (Tdjeersma and Militz 2005;Esteves et al 2013;Chen et al 2014;Tolvaj et al 2014b;Fabiyi and Ogunleye 2015) may be helpful in understanding temperature-induced ageing (Matsuo et al 2011).…”