Permeability of Eucalyptus wood improved by microwave treatment
Xia He, Xianjun Li, Jie Xie, Xingyang Xiong
The wood species with low permeability may cause many problems during timber manufacturing. Extreme difficulties take place in fabricating new wood-based composites by impregnating low- permeability timber with functional materials, such as flame retardant, preservatives and resins. Microwave (MW) treatment can increase the permeability of wood both in transverse and longitudinal directions. The effects of MW radiation time, MW radiation power and initial moisture content (MC) on permeability of wood were investigated in this study. The results showed that the permeability (both transverse and longitudinal direction) of wood significantly increased by the MW treatment; the wood permeability increased with the increasing MW radiation power and radiation time, but decreased with increasing initial wood moisture content. Microwave treatment had a more significant effect on the permeability of Eucalyptus (Eucalyptus urophulla) wood on longitudinal direction than that on transverse direction. Compared with the control group, the weight gain percentage of transverse and longitudinal directions of wood increased from 0.80% to 57.53% and 22.49% to 125.88% respectively when radiation time increased from 30s to 90s; when radiation power increased from 5kw to 20kw, the weight gain percentage of transverse and longitudinal directions increased from 1.50% to 21.8% and5.57% to 134.63% respectively; The samples with 25% initial MC showed the biggest stain absorption as 11.79g and 5.47g in transverse and longitudinal directions respectively. MW treatment generated high internal steam pressure, resulting in the rupturing of wood cell pore membranes, ray cells. Therefore, the great increase of permeability can be achieved and created favourable conditions for the fabrication of high value-added functional wood based composites materials.