Physical-mechanical properties and weathering performance of poplar and spruce wood with various tung oil loadings

Applying tung oil (TO) in wood modification provides a green strategy for improving the performance of wood and promoting the application of TO. Nevertheless, the relationship between TO polymer loading and wood properties (physical-mechanical properties and weathering resistance) is unclear. Hence, by controlling the concentrations of TO solution, TO-treated woods (poplar and spruce) with different TO polymer loadings were prepared through the impregnation technique in this work. The resulting wood's density distribution, micromorphology, physical and mechanical properties, and weathering performance were comprehensively investigated. Results indicated that poplar wood exhibited a higher loading capacity than spruce wood. TO polymer was evenly distributed in poplar wood, except for the pure TO-treated samples. For spruce wood, the loading in earlywood was higher than that in latewood. TO treatment endowed wood with excellent water uptake and sorption and moderate ASE values (31.8 % for poplar and 23.3 % for spruce). TO impregnation had a negligible impact on the wood bending strength, while the impact bending strength was increased by 23 % for poplar wood (50 % TO) and 21 % for spruce wood (70 % TO). After artificial weathering, TO-treated wood with higher polymer loading exhibited higher color stability. The presence of the TO polymer could prevent the wood components from aging degradation by counteracting weathering and improving water resistance.