Evaluation of dimensional stability, surface roughness, colour, flexural properties and decay resistance of thermally modified Acacia auriculiformis

This paper presents the effect of thermal modification of 14-15 year-old plantation grown Acacia auriculiformis wood in the 150-240ºC temperature range under vacuum condition. Important techno-mechanical parameters of thermally modified wood such as density, dimensional stability, colour, surface roughness, decay resistance against brown and white rot fungi and flexural properties were evaluated and compared with control. Depending on severity of heat treatment, colour of modified sapwood was turned from light to dark brownish. Moreover, the change in colour was found to be uniform throughout the thickness of wood blocks. Amount of shrinkage of Acacia auriculiformis wood was observed to be decreased with increasing treatment temperatures. Maximum dimensional stability of wood thermally modified at 240ºC was in the range of 60-65%. The surface roughness parameters (Ra and Rz) were reduced significantly after the treatment. The flexural strength (modulus of rupture-MOR) was observed to be reduced with increasing treatment temperatures. However, flexural stiffness (modulus of elasticity-MOE) was not found to be affected significantly up to 210ºC temperature. The lower amount of weight loss of thermally modified wood compared to untreated control showed improved decay resistance against white and brown rot fungi. With desirable improvements in various esthetic and technologically important quality parameters such as enhanced dimensional stability, biological durability against fungi and certain other properties, thermally modified wood from short-rotation Acacia auriculiformis may be considered as viable alternative to scarcely available timber resource for different value-added applications