Abstract
Thermal modification of wood causes chemical changes that significantly affect the physical, mechanical and biological properties of wood; thus, it is essential to investigate these changes for better utilization of products. Fourier transform infrared spectroscopy and size exclusion chromatography were used for evaluation of chemical changes at thermal treatment of oak wood. Thermal modification was applied according to Thermowood process at the temperatures of 160, 180 and 210 °C, respectively. The results showed that hemicelluloses are less thermally stable than cellulose. Chains of polysaccharides split to shorter ones leading to a decrease of the degree of polymerization and an increase of polydispersity. At the highest temperature of the treatment (210 °C), also crosslinking reactions take place. At lower temperatures degradation reactions of lignin predominate, higher temperatures cause mainly condensation reactions and a molecular weight increase. Chemical changes in main components of thermally modified wood mainly affect its mechanical properties, which should be considered into account especially when designing various timber constructions.
Highlights
Wood is a sustainable and environmentally friendly natural material used for both structural and non-structural applications
The goal of this study is to examine the chemical changes of oak wood main components by Fourier-transform infrared spectroscopy (FTIR) and size exclusion chromatography (SEC), in thermally modified wood in order to clarify the processes of structural changes in wood polymers better
Hemicelluloses degraded more rapidly, and the decrease of non-glucose saccharides was observed in thermally treated oak wood [4]. This process is more evident at the temperature of 180 ◦ C leading to a decrease of degree of polymerization (DP) and an increase of polydispersity
Summary
Wood is a sustainable and environmentally friendly natural material used for both structural and non-structural applications. Thermal modification (TM) is environmentally friendly and one of the most effective pretreatment methods to enhance the dimensional stability and decay resistance of wood without using any toxic chemicals. The modified wood composition results in a lower hygroscopicity with a major influence on both dimensional stability and durability [6]. It appears that the higher the treatment temperature, the better the durability, stability and biological properties of the product become.
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