Effect of thermal treatment on the chemical characteristics of wood from Eucalyptus grandis W. Hill ex Maiden under different atmospheric conditions

Abstract

Thermal treatment (thermal rectification) is a process in which technological properties of wood are modified using thermal energy, the result of which is often value-added wood. Thermally treated wood takes on similar color shades to tropical woods and offers considerable resistance to destructive microorganisms and climate action, in addition to having high dimensional stability and low hygroscopicity. Wood samples of Eucalyptus grandis were subjected to various thermal treatments, as performed in presence (140ºC; 160ºC; 180ºC) or in absence of oxygen (160ºC; 180ºC; 200ºC) inside a thermal treatment chamber, and then studied as to their chemical characteristics. Increasing the maximum treatment temperatures led to a reduction in the holocellulose content of samples as a result of the degradation and volatilization of hemicelluloses, also leading to an increase in the relative lignin content. Except for glucose, all monosaccharide levels were found to decrease in samples after the thermal treatment at a maximum temperature of 200ºC. The thermal treatment above 160ºC led to increased levels of total extractives in the wood samples, probably ascribed to the emergence of low molecular weight substances as a result of thermal degradation. Overall, it was not possible to clearly determine the effect of presence or absence of oxygen in the air during thermal treatment on the chemical characteristics of the relevant wood samples.

Effect of the Brazilian thermal modification process on the chemical composition of Eucalyptus grandis juvenile wood: Part 1: Cell wall polymers and extractives contents

“…The same statistical behavior was reported by Moura et al (2012), for the same treatments and species as in this study. The difference was that they thermally modified wood in laboratory scale, with an oxygen (O 2 ) atmosphere.…”

“…There are few published studies about the chemistry of thermally modified Eucalyptus grandis wood, but we found a very similar Brazilian study where the process was carried out in laboratory scale with a nitrogen (N 2 ) atmosphere (Moura, Brito and Silva Júnior 2012). The authors reported higher averages of holocellulose content for thermally modified 18-year-old (the same age as in this research) Eucalyptus grandis wood than we found, with 58,95 and 54,84% respectively for treatments at 160 and 180 °C.…”

“…According to some authors who have studied Eucalyptus spp. (Brito et al 2008, Esteves et al 2008, Moura et al 2012, when some extractives are volatilized, new substances are produced from degradation of hemicelluloses (mainly) and lignin, and part of these new substances are also volatilized. Further research will be carried out about the qualitative nature of the extractives of thermally modified Eucalyptus grandis wood.…”

“…Some laboratorial scale studies have been performed about thermal modification of eucalyptus wood, mostly Eucalyptus globulus (Esteves et al 2007a, Esteves et al 2007b, Esteves et al 2008 from Portugal, Eucalyptus grandis (Batista and Klitzke 2010, Batista et al 2011, Calonego et al 2010, Moura et al 2012, Pessoa et al 2006, Pincelli et al 2002 and Eucalyptus saligna (Brito et al 2008) from Brazil.…”

Propriedades Físicas da Madeira Termorretificada de Quatro Folhosas

“…A termorretificação apresenta estudos que indicam sua eficácia na melhora da estabilidade dimensional e do aumento da resistência à degradação biológica e ao intemperismo (Moura et al, 2012). Embora esse processo não esteja consolidado no Brasil, no continente europeu, a madeira termorretificada é largamente empregada na confecção de produtos, como: decks, móveis para jardim, esquadrias, armários internos, parquet, painéis decorativos e interior de saunas (Esteves & Pereira, 2009).…”