Enhanced strength and chemical stability of Salix tetrasperma wood through thermal modification

Thermal modification of Salix tetrasperma wood was conducted at temperatures ranging from 60 to 200 °C for durations of 2, 4, and 6 h to evaluate changes in its chemical and mechanical properties. The treatment induced notable alterations in extractives and structural components. Peak values for cold-water (7.44%) and hot-water (11.56%) soluble extractives were recorded at 140 °C and 120 °C, respectively, while the lowest values (5.17% and 8.76%) occurred at 200 °C. Alcohol-benzene extractives and lignin content increased with temperature, reaching maxima of 13.61% and 24.77% at 200 °C, compared to 9.03% and 16.49% in the untreated control. Conversely, holocellulose content showed a declining trend with heat, dropping from 79.18% in the control to 70.89% at 200 °C. Mechanically, tensile strength peaked at 0.059 kN/mm² at 140 °C and declined to 0.040 kN/mm² at 200 °C. Bending strength was highest in the control (0.010 kN/mm²) and lowest (0.007 kN/mm²) at 180 °C and 200 °C. Compression strength parallel to grain reached its maximum at 160 °C (0.037 kN/mm²), whereas perpendicular compression was highest in the control (0.031 kN/mm²). Minimum compression values were noted at 200 °C. These results underscore the potential of thermal modification to strategically tailor the physico-chemical properties of Salix tetrasperma wood, improving its dimensional stability, durability, and overall performance for industrial and structural applications.