Effects of Industrial Heat Treatment on Some Physical and Mechanical Properties of Iroko Wood

The purpose of this study was to determine the effect of industrial heat-treatment (ThermoWood) effect on some important properties (density, anti-swelling efficiency (ASE), electrical resistance, strength, hardness and color) of Iroko wood (Chlorophora excelsa). Samples were subjected to heat treatment at 190 °C for 120 min during the main heat treatment period (the total time of the process was 60 hours). The results showed that the applied process caused 4.6 % decrease in density. Dimensional stability was considerably improved, with ASE values of 13.2 %. The color became darker after treatment. The process caused a significant (p<0.05) reduction (3.35 to 25 %) of all investigated mechanical properties at a specific moisture level (12 %). However, the mechanical properties of wood are closely related to its moisture content, and heat-treated wood is less hygroscopic than untreated wood. After long-term acclimatization, most heat-treated samples had almost half the equilibrium moisture content of control samples. Although heat treated samples have lower water content and higher electrical resistance at the same soaking time, the obtained data clearly showed that heat treated samples had a slightly lower electrical resistance for the same moisture content compared to control samples.