Thermochemical and physical properties of two fast-growing eucalypt woods subjected to two-step freeze heat treatments

In this study, the effect of two-step freeze-heat treatments on the thermochemical and physical properties of two Eucalyptus wood were investigated. Five treatments were performed and compared to untreated control: freezing (WF), freezing followed by heat treatment at 180 and 200 degrees C (WFT180 and WFT200) and heat treatment at 180 and 200 degrees C (WT180 and WT200). The freeze step was performed at -22 degrees C for 72 h and the heat step was performed at 180-200 degrees C for 3.5 h. Thermochemical (wet chemical analysis, FTIR and TGA), physical (water absorption and ASE) and surface properties (wettability) were measured. The two-step freeze-heat treatments changed the holocellulose and extractives contents, and stabilized the 1% NaOH solubility. Dimensional stability increased and hygroscopicity of thermally treated eucalypt wood decreased. The two-step treatments resulted in lower chemical changes than the application of a heat treatment only. The apparent contact angle of thermally treated wood increased, confirming the improvement of wood hydrophobicity. (C) 2015 Elsevier B.V. All rights reserved.