Effect of Microwave Pretreatment on Permeability and Drying Properties of Wood

Abstract

A microwave (MW) treatment of plantation eucalyptus (Eucalyptus urophylla) wood was investigated by applying MW treatments with varying conditions, such as radiation power, irradiation time, and initial moisture content of the wood. The wood permeability and drying properties were investigated. Results show that the permeability (both along the transverse and longitudinal directions) increased with the radiation power and the irradiation time. The permeability was considerably enhanced by the MW pretreatments, which effectively decreased the moisture content within the wood. A MW pretreatment can greatly accelerate the drying rate and shorten the wood drying time. Under atmospheric pressure the stain uptake along the transverse and longitudinal directions, with respect to the wood fibers, increased to 58% and 135%, respectively, compared to reference samples. Meanwhile, the drying rate increased to 171% and the drying time was cut by 65%. The MW pretreatment was found to generate a high-pressure internal steam that resulted in the rupture of wood cell pore membranes and ray cells. Therefore, a remarkable permeability increase and drying time reduction was achieved, which created favorable conditions for the fabrication of high value-added functional wood-based composites materials.