Improving structural integrity and dynamics of lignocellulosic polymers in heat-treated wood with tung oil.

Wood is a renewable material rich in lignocellulosic macromolecules and is valued for its sustainability while facing durability challenges under environmental conditions. Heat treatment improves wood properties by modifying the structure of polysaccharides and lignin, but often compromises its mechanical properties. This study investigates the use of natural tung oil to reinforce these biopolymers in heat-treated wood. Tung oil-treated wood (HT wood) demonstrated superior thermal stability, better control of exothermic reactions, and enhanced mechanical performance. Compared to air-treated wood (HT wood), Young's modulus of HT wood increased by 40.4 % at 210 °C, with reduced viscoelastic relaxation and consistent suppression of creep displacement. HT wood exhibited a higher initial storage modulus and a new relaxation phase at 0-50 °C, with activation energy of 252.4-338.7 kcal/mol, while HT wood showed lower modulus values, a broader relaxation phase (0-100 °C), and activation energy of 237.6 kcal/mol. Tung oil restricted the micro-Brownian motion of cell wall components, increased cell wall thickness by 10.7 %, and mitigated the thermal degradation of wood components by protecting crystalline cellulose, lignin, and cross-linked products from structural disruption. These results highlight that tung oil is a sustainable modifier to extend the use of heat-treated wood in structural engineering.