Comparative study on the durability of heat-treated White Birch (Betula papyrifera) subjected to the attack of brown and white rot fungi

Abstract

The effect of heat treatment on decay resistance of white birch was evaluated for different incubation periods ranging from 2 to 12 weeks using three species of brown rot and one species of white rot fungus. The results of weight loss tests showed that the white rot fungus, Trametes versicolor, effectively degraded the untreated wood (73.5%). While the degradation of untreated wood by brown rot fungi species, Gloephyllum trabeum (11.6%) and Conifora puteana (6.2%), was considerably less compared to T. versicolor, the third brown rot fungi studied, Poria placenta, caused an appreciable degradation of the same species (52.4%). The results clearly showed that the heat treatment reduced the effect of fungi attack on white birch. Increasing the heat treatment temperature from 195 to 215°C resulted in reduction of weight loss, consequently, reduction in fungal attack. As an example, the weight loss reductions due to T. versicolor, P. placenta, G. trabeum and C. puteana attack was 62.2%, 71.3%, 89.6% and 100%, respectively, compared to the weight loss of untreated wood when it is heat treated at 215°C. Thus, these results confirmed that the heat treatment increased the biological resistance of white birch.     

Effect of thermal modification temperature on the mechanical properties,dimensional stability,and biological durability of black spruce (Picea mariana)

This study was aimed at evaluating the effect of thermal modification temperature on the mechanical properties, dimensional stability, and biological durability of Picea mariana. The boards were thermally modified at different temperatures 190, 200 and 210 °C. The results indicated that the thermal modification of wood caused a significant decrease in the modulus of rupture (MOR) after 190 °C, while the modulus of elasticity (MOE) seemed less affected with a slight increase up to 200 °C and slight decrease with further increase in temperature. The hardness of the thermally modified wood increased in the axial direction. This increase was also observed in tangential and axial directions but at a lesser extent. The final value was slightly higher in axial direction and lower in radial and tangential directions compared to those of the untreated wood. Dimensional stability improved with thermal modification in the three directions compared to the dimensional stability of unmodified wood. The fungal degradation results showed that the decay resistance of thermally modified wood against the wood-rotting fungi Trametes versicolor and Gloephyllum trabeum improved compared to that of the untreated wood. By contrast, the thermal modification of P. mariana had a limited effect on the degradation caused by the fungus Poria placenta.