Hygroscopicity and dimensional stability of Populus euramericana Cv. modified by furfurylation combined with low hemicellulose pretreatment

Abstract

Hygroscopicity and dimensional instability usually impair the service of wood products. To upgrade the property, fast-growing poplar wood (Populus euramericana Cv.) was treated with furfuryl alcohol at a concentration of 25% combined with low hemicellulose pretreatment. Equilibrium moisture content and dimensional changes were measured within the range of 0–96% relative humidity (RH) at 25 °C. New voids caused by hemicellulose loss suggested by the scanning electron microscope contributed to higher weight percent gain of furfural resin with more obvious bulking of cell walls. The size distribution of mesopores increased after low hemicellulose pretreatment but decreased much more after furfurylation from the analysis of nitrogen adsorption. After hemicellulose loss, moisture sorption was weakened indicated from the decrease in moisture content (MC) and hydrated MC as well as dissolved MC due to the decrement of accessible hydroxyl groups calculated by Hailwood–Horrobin theory. Furthermore, dimensional stability was improved. Furfurylation led to further reduction in moisture sorption and enhancement of dimensional stability, since water paths were blocked and less hydroxyl groups were accessible. The bulking also limited the swelling of cell walls. After the combined modification, over 45% reduction in moisture content and dimensional changes of wood at 60% RH can be achieved. Such upgraded fast-growing wood could be utilized more widely with a longer service life as a potential replacement for traditional high-quality solid wood and helpful with building a more efficient and environmentally friendly material industry.