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

Abstract

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.

Keywords:

• Biological resistance
• dimensional stability
• mechanical properties
• Picea mariana
• thermally modified wood
• wood-rotting fungi

Acknowledgments

The authors thank Dr Yasar Kocaefe, Dr Noura Oumarou, and Ms Claire Fournier for their help during the heat treatment trials. The financial support of NSERC, UQAC, and FUQAC (Foundation of University of Quebec at Chicoutimi) is greatly appreciated.