Eco-friendly densified wood obtained by combining urea and hot-pressing treatment

Wood densification treatment is a process that effectively improves the soft texture of fast-growing wood, thus enhancing its mechanical properties. However, the densification process often causes cell wall damage and significant compression set recovery in densified wood, significantly limiting its applications. To address these limitations, urea-pretreated densified wood (UPDW) was developed in this study using different concentrations of urea solution. The UPDW exhibited enhanced dimensional stability and mechanical properties. The UPDW exhibited a reduced compression set recovery of 1.6–4.6 % and thickness moisture swelling of 0.9–2.3 %, which decreased by 86.8 % and 71.9 %, respectively, compared with water-pretreated densified wood, indicating superior dimensional stability. Additionally, UPDW exhibited enhanced modulus of rupture (MOR) (50.7–67.0 MPa) and modulus of elasticity (MOE) (5.5–6.4 GPa). The MOR and MOE of the optimized 50 %-UPDW increased by 41.6 % and 28.0 %, respectively, compared with the natural wood (NW). Additionally, the surface hardness of 50 %-UPDW was significantly enhanced (50.6–59.3 HD), which was 39.6 % higher than that of NW. Notably, 89.5 % of the urea in the 50 %-UPDW decomposed into gases and escaped, leaving a small amount of urea. Therefore, the UPDW demonstrates great potential application in construction and furniture materials.