Developing a Unilaterally Surface-Densified Wood Composite with Excellent Performance through Surface Impregnation of Furfuryl Alcohol Resin

Developing a unilaterally surface-densified wood material with high mechanical performance and excellent dimensional stability from fast-growing wood is highly desirable for furniture and building applications. Here, we propose a green and efficient synergistic modification technology that can endow the fast-growing wood with excellent performance. Specifically, the wood samples were unilaterally surface-impregnated with furfuryl alcohol (FA) aqueous solutions, followed by in situ polymerizations of FA solutions within the wood structure during unilateral surface densification. Benefiting from the formation of a water-resistant FA cross-linked network in the wood structure, the FA-impregnated and unilaterally surface-densified wood (IUSD-wood) exhibited dramatically improved dimensional stability. The densified layer impregnated at 30 wt % FA concentration yielded maximum thickness swelling values of 3.7% and 12.3% after moisture and water absorption, which were decreased by nearly 90% compared to that without FA impregnation. Furthermore, the FA resin filling also led to the increase of peak density and effective dense layer thickness as well as densification degree in IUSD-wood, thus further improving the mechanical properties. Meanwhile, the IUSD-wood provided a similar visual feeling to the precious tropical hardwood species. This synergistic modified approach widens the potential of low-quality poplar wood to replace hardwood for construction and interior decoration applications.