Performance improvement of poplar wood based on the synergies of furfurylation and polyethylene glycol impregnation

Fast-growing wood usually exhibits dimensional instability and inferior mechanical strength, which severely obstructs its wide application. To improve the dimensional stability and mechanical strength, biomass-derived furfuryl alcohol combined with polyethylene glycol (PEG) was vacuum-impregnated into wood hierarchical structures, causing cell wall bulking and porosity reduction. Furfural resin and PEG distributed in cell lumina, cell walls and middle lamella regions indicated by analyses of scanning electron microscope and fourier transform infrared spectroscopy. Wood porosity was generally reduced and the specific surface area decreased by over 65% analyzed by the nitrogen absorption. Consequently, wood hydrophobicity and dimensional stability were highly improved, and the water absorption and volumetric change decreased by over 55% and 78%. The flexural strength and modulus elasticity were improved by over 49% and 46%. Furfural resin helped the fixation of PEG in wood and significantly reduced PEG leaching. PEG with flexible linear molecular structure formed interpenetrating polymer network in wood hierarchical structures with furfural resin and reduced self-crosslinking of furfural resin. Accordingly, the impact toughness of compound modified wood increased by 39% compared with solely furfurylated wood. This study provided efficient and sustainable concepts to facilitate better industrialized application of wood furfurylation and improve service value of fast-growing wood.