Effect of high temperature treatment of Hevea brasiliensis on density, strength properties and resistance to fungal decay

Abstract

Plantation grown Hevea brasiliensis (rubberwood)—a tropical wood species of low natural durability was thermally processed at four temperatures in the range of 150–240 °C for different durations under vacuum. Effect of heat treatments on various important physical and mechanical properties such as weight loss, density, flexural strength (modulus of rupture—MOR), stiffness (modulus of elasticity—MOE), compressive strengths and surface hardness as well as decay resistance were evaluated and compared with untreated wood. The weight loss due to heat treatments was found to be in the range of 1.0–14.6%. Density and flexural MOR were found to decrease with increasing temperature (up to 210 °C), while flexural MOE, compressive strengths and hardness were not much affected. Higher treatment temperatures (210–240 °C) were observed to have deleterious effect on the mechanical strength of wood. Heat treated rubberwood showed excellent durability against brown rot (Polyporus meliae) and white rot (Coriolus versicolor) fungi as evidenced by lower amount of weight loss of exposed samples. The decay resistance was found to increase with severity of treatments. Based on improved durability and moderate variations in mechanical properties due to relatively mild heat treatments (180–210 °C), thermally modified rubberwood is found to be suitable for certain nonstructural applications. Moreover, heat-treated rubberwood may also be considered as an ecological alternative to chemically impregnated wood which offers many potential and attractive opportunities to the timber processing and product industry for commercial market.