Comparative study on the properties of Eucalyptus urophylla wood modified by thermal treatment at different temperatures combined with paraffin impregnation

Plantation Eucalyptus urophylla wood has poor dimensional stability, limiting its utilization. Thermal modification and paraffin impregnation are effective, eco-friendly treatments, but their combined effects across parameters are not well established. This study systematically evaluated synergistic outcomes of three thermal levels (150 °C, 170 °C, and 190 °C) combined with paraffin impregnation (2h and 4 h) on eucalyptus wood properties. The results demonstrated that all combined treatments significantly improved wood performance, though outcomes were temperature-dependent. The 150/4P treatment optimally balanced key properties: it reduced hygroscopic swelling, equilibrium moisture content, and water absorption by 63%, 61%, and 58%, increased modulus of elasticity by 23%, and uniquely enhanced MOR by 18%. In contrast, higher temperatures (170/4h, 190/2h) achieved greater dimensional stability (72% and 80% swelling reduction) and higher MOE gains (27% and 33%), but at the cost of MOR loss (20% and 16%) and more pronounced colour darkening. Comprehensive evaluation, considering dimensional stability, mechanical property retention, and aesthetics, indicates that 150/4P offers the best overall performance balance, presenting a superior modification strategy for high-value eucalyptus wood utilization.