Bioresistance of poplar wood compressed by combined hydro-thermo-mechanical wood modification (CHTM): Soft rot and brown-rot

This work studied fungal bioresistance of combined hydro-thermo-mechanically modified (CHTM) poplar wood. The CHTM technique, introduced by Mohebby et al. (2009), is a combination of two wood modification techniques-hydrothermal wood modification and densification of wood. Blocks of poplar wood were initially treated hydrothermally at temperatures of 120, 150, and 180 °C for holding times of 0, 30, and 90 min. Afterwards, the treated blocks were compressed by a hot press (160 and 180 °C) for 20 min with a compression set of 60%. After the CHTM-treated blocks were dried, small specimens were cut for soft-rot and brown-rot decay tests according to ENV 807 and EN 113. Mass losses as well as metabolic moisture contents were determined in the decayed samples. Results revealed that the combination of wood modification techniques showed fungal suppression. It was also found that the hydrothermal treatment step could significantly reduce fungal attack in comparison with densification. Reduction of the mass losses was associated with the hydrothermal treatment temperature. Also, the level of metabolic moisture content was correlated with the mass losses for both fungi. Any reduction of the mass loss decreased the moisture content in the wood.