Effects of environmental conditions on physical and mechanical properties of thermally modified wood

The behaviour of industrially modified wood has not been systematically evaluated in controlled exposure conditions. The objective of this study was to assess the equilibrium moisture content (EMC), dimensions, and Brinell hardness of thermally modified wood in different temperature and relative humidity (RH) conditions. Tested materials consisted of European ash (Fraxinus excelsior), Norway spruce (Picea abies), and Scots pine (Pinus sylvestris), thermally modified with industrial Thermowood® processes into grades, Thermo S and Thermo D. The properties were measured at 20 °C, 65% RH; 10 °C, 90% RH, and 30 °C, 30% RH conditions. The results show that the reduction of EMC and the improvement in dimensional stability are dependent on the degree of thermal modification. Thermal modification was more resistant in moisture absorption at 20 °C, 65% RH than at 10°C, 90% RH and 30°C, 30% RH, and the more severe modification decreased the difference between different exposure conditions. The tangential-radial ratio of swelling and shrinkage was higher for thermally modified than non-modified wood. Brinell hardness of modified pine and spruce did not differ significantly from non-modified wood in normal and dry conditions, but the more humid conditions increased the difference by 12-17%.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author