Physical and Mechanical Properties of Gmelina Wood (Gmelina arborea Roxb.) Modified with Furfuryl Alcohol-Tannin

Furfurylation, a renowned chemical modification technique, uses furfuryl alcohol to enhance the properties of wood. This technology can be further refined by incorporating renewable tannins, which promote cross-linking with furfuryl alcohol. This study investigates the effects of furfurylation and tannin-modified furfurylation on the physical and mechanical properties of tropical Gmelina wood (Gmelina arborea Roxb.). Experiments involved impregnating Gmelina wood with aqueous solutions of furfuryl alcohol (FA) at 40% and 70% concentrations, as well as FA-tannin combinations (FA 40%-TA and FA 70%-TA), followed by polymerization at 103°C. The results demonstrated that both FA and FA-tannin treatments significantly improved the wood’s physical and mechanical properties. Notably, FA-tannin treatments achieved anti-swelling efficiency comparable to FA alone. However, the addition of tannins (FA 70%-TA) enhanced leaching resistance by up to 47%, contributing to a more environmentally sustainable modification process. Mechanically, the inclusion of tannins in FA 70%-TA slightly increased the modulus of elasticity (14%~8732 kg/cm2) and the modulus of rupture (9%~40.9 kg/cm2). Furthermore, the tannin addition imparted a darker color to the modified wood, enhancing its aesthetic appeal. This study highlights the potential of tannin-modified furfurylation to advance wood modification technology, combining improved performance with environmental benefits.