Improved performance of poplar wood by an environmentally-friendly process combining surface impregnation of a reactive waterborne acrylic resin and unilateral surface densification

To improve the undesirable intrinsic properties of plantation wood, this study presents the development of unilaterally surface-densified wood with high dimensional stability, surface hardness, and bending property for value-added applications. Poplar wood (Populus euramevicana cv. ’I-214′) was surface impregnated with a reactive waterborne acrylic resin followed by unilateral surface densification and equilibration. The influence of resin weight percent gain (WPG) and compression temperature on the physical and mechanical properties were investigated. Results indicated that the waterborne acrylic resin permeated into cell lumens and cured to form a rigid three-dimensional, water-resistant network. Set-recovery (SR) of the surface densified layers decreased dramatically when the deformation was fixed by the cured resin. A higher resin WPG resulted in a lower SR. Densified layers with WPG lower than 4.7% yielded SR values lower than 2.0%. Surface properties of the surface densified wood were dependent on resin WPG and compression temperature. Surface hardness increased significantly with increasing resin WPG. Samples with WPG higher than 3.4% had a static hardness of 5.9 kN, which is more than double that of the un-densified control. Thickness of the effective dense layer and total dense layer increased with increasing WPG and compression temperature. The modulus of rupture (MOR) and modulus of elasticity (MOE) of the only surface densified (OSD) wood increased 28.2% and 37.6%, respectively, compared with the un-densified control. Samples with low WPG had comparable MOR and MOE to the OSD wood. The resin-impregnated and surface densified wood with excellent performance is suitable for flooring, desktop, tabletop, bathroom cabinet applications.