Effects of hemicellulose removal combined with polyethylene glycol impregnation on dimensional stability of wood

To investigate the combined effects of hemicellulose removal and polyethylene glycol (PEG) impregnation on the dimensional stability of wood, Cunninghamia lanceolata (Lamb.) Hook. was hydrothermally treated and vacuum-impregnated with PEG. About 19.43% hemicellulose was removed, which partially facilitated the penetration and uniform distribution of PEG in wood cells suggested by SEM and FTIR analyses. The mass and volume increase as well as cell wall bulking were positively correlated with PEG concentration. Both solely hemicellulose removal and PEG treatment enhanced wood dimensional stability. The wood after combined treatments exhibited much better dimensional stability mainly due to water path block, cell wall bulking and sorption site reduction calculated by Hailwood-Horrobin theory. Moreover, higher PEG impregnation combined with hemicellulose removal caused lower water absorption, and the corresponding ASE reached 68%. Moisture sorption of wood after combined treatment was lower below about 77.6% RH, but then increased sharply because PEG 2000 became more hygroscopic at higher RH. The results confirmed the efficiency of combined modification on improving dimensional stability of wood and also indicated the importance of appropriate use of PEG in moisture sorption. The study could potentially provide useful knowledge of developing new modification techniques to improve wood dimensional stability for better utilization.