Chemical Composition and Selected Physical Properties of Oak Wood (Quercus robur L.) Modified by Cyclic Thermo-Mechanical Treatment

Abstract

Oak wood (Quercus robur L.) was subjected to cyclic thermo-mechanical treatment (CTMT). The temperature of the press platens during the CTMT was either 100 °C or 150 °C. The equilibrium moisture content and the dimensional changes of the oak wood were examined when it was exposed to 9 to 98% relative humidity at 20 °C (± 2 °C). Densified oak wood had lower equilibrium moisture content than the non-densified wood for the relative humidity ranges examined. Furthermore, when the temperature of the thermo-mechanical modification was higher, the equilibrium moisture content of the wood was lower. Thermo-mechanical modified wood was characterised by higher swelling values in the radial direction than in the tangential direction. When the temperature of the CTMT was higher, the water absorption of the wood was lower. The number of treatment cycles significantly influenced the water absorption of the oak wood at its maximum saturation. After CTMT, changes were observed in oak wood, in particular, with regards to soluble substances in 1% NaOH and to chloroform-ethanol extractives.