Influences of Combined-Hydro-Thermo-Mechanical (CHTM) Modification on Moisture Absorption and Dimensional Stability of Poplar Wood

In this research work, it was planned to study influences of hydrothermal treatment temperature, holding time and press temperature on wood density, spring back, moisture absorption as well as dimensional stability of combined-hydro-thermo-mechanically modified poplar wood. Wood blocks were treated hydrothermally at temperatures 120, 150 and 180°C for holding time of 0, 30 and 90 min. Afterwards, those blocks were compressed immediately in a press at temperatures 160 and 180°C for 20 min with a compression set of 60% in radial direction. Density, spring back, moisture absorption and dimensional stability of treated samples were determined and compared with the untreated ones. Results revealed that density was increased due to the treatment. Spring back was reduced by raise of hydrothermal treatment temperature. Moisture absorption was also decreased by treatment temperature. Although, any increase of relative humidity caused increase of moisture content in compressed wood, however it was less than that of untreated one. Any extended holding time had no significant effects on moisture absorption. There was also a reductive effect of press temperature on moisture contents. Radial swelling of treated samples was also reduced by gained treatment temperature. Press temperature also decreased the swelling; however, it was not as much as the treatment temperature. Generally, this research work indicated proper capability of this innovated combined-hydro-thermo-mechanical wood modification on properties of compressed wood to be used practically.