Improving the weathering properties of heat-treated wood by acetylation

Abstract Heat-treated wood is widely used for outdoor furniture manufacturing. However, it is susceptible to against physical degradation such as cracking and discoloration. This study involved heat-treated wood at three different temperatures of 180 °C, 200 °C and 220 °C was acetylated using vacuum-pressure impregnation methods to enhance photostability, dimensional and thermal stability. The laboratory chromaticity data indicated a substantial enhancement of the photostability of the acetylated heat-treated wood. The color difference was reduced from 11.89 to 10.08 for the 180 °C treatment, then from 10.24 to 9.02 for the 200 °C treatment, and from 8.31 to 8.11 for the 220 °C treatment compared to unmodified wood at the same temperature. The microstructure analysis and chemical composition study suggested that the hydroxyl groups were greatly reduced, rendering the microstructure and chemical composition of wood relatively stable. In addition, the results of water contact angle, water absorption, swelling and shrinking data show that acetylated wood exhibits lower hydrophilicity and greater dimensional stability. Thermo-gravimetric analysis reveals that acetylated wood maintained better thermal stability, as evidenced by the greater maximum temperature for thermal degradation. The weathering resistance of heat-treated wood was significantly improved by acetylation treatment.