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Changes caused by heat treatment in chemical composition and some physical properties of acacia hybrid sapwood

Abstract Acacia hybrid (Acacia mangium×auriculiformis) sapwood was heat-treated in nitrogen under laboratory conditions for 2–6 h at 210°C–230°C. Chemical composition and physical properties including water absorption and swelling were examined. The results showed that these properties were reduced significantly by heat treatment, and there is an interactive effect of temperature and time on them. Chemical changes of the wood surface were determined by X-ray photo-electron spectroscopy analysis. Results indicate that the O/C ratio decreases as a function of treatment intensity due to the migration of extractives and degradation products to the surface during heat treatment. The C1s peaks showed an elevated content of lignin and extractives, whereas the hydroxyl group content was diminished with elevated treatment temperature. The O1s peaks revealed an increase in the O1 peak and confirmed the course of C1s peaks. These results coincide with the decrease in water absorption and swelling of wood after heat treatment.