Improvement of water resistance, dimensional stability, and mechanical properties of poplar wood by rosin impregnation

Rosin was used to improve the physical and mechanical properties of fast-growing poplar wood using the impregnation method. The rosin was dissolved in ethanol with different concentrations and the wood was impregnated with the solutions obtained. The weight percent gain, density, equilibrium moisture content (EMC), anti-swelling efficiency (ASE), and mechanical properties of the treated wood were measured in detail. The crystalline structure, morphology, rosin distribution, and dynamic wettability were also evaluated. Results showed that the density of the wood increased from 0.34 to 0.44 g/cm³ after the treatment with 20 % rosin solution. When the rosin content increased by 5, 10, 15 and 20 %, the ASE after 5 days water immersion increased to 15.6, 20.6, 30.3 and 36.0 % and EMC reduced by 17.8, 26.5, 36.2 and 42.7 %, respectively. Particularly, the modulus of rupture, modulus of elasticity, and compression strength of the 20 % rosin impregnated wood increased by 12.8, 18.9, 31.6 %, respectively. In addition, the dynamic wettability of wood was significantly changed by the rosin treatment. The rosin within wood could occupy the wood lumens, cell corners, and middle lamella, and partly penetrated wood cell walls, which was revealed by field emission scanning electron microscope and confocal laser scanning microscope.