Improvement of technological quality of eucalypt wood by heat treatment in air at 170-200 °C
2007
Esteves, B. | Domingos, I. | Pereira, H.
Eucalypt wood is a low-value wood considered a nondurable species with low dimensional stability, used almost exclusively for pulp and paper or as firewood. The heat treatment was made in an oven in the presence of oxygen during 2 to 24 hours and temperatures of 170 to 200 degrees C. Mass loss with treatment, equilibrium MC, dimensional stability measured as ASE in radial and tangential directions and at 35 percent, 65 percent and 85 percent relative humidity, MOE, bending strength and wettability were determined. Mass loss increased with treatment time and temperature reaching 9.5 percent for wood treated at 190 degrees C for 24h. Equilibrium MC decreased more than 50 percent (at 35 percent relative humidity) reaching a maximum of 61 percent reduction. At higher air relative humidity the reduction was smaller, 49 percent and 38 percent at the most for 65 percent and 85 percent relative humidity. Dimensional stability (ASE) increased with maximum values of 88 percent and 96 percent in radial and tangential direction, respectively. The improvement was higher for lower relative humidity. There was a reduction on mechanical resistance with heat treatment especially for bending strength that decreased about 20 percent for 3 percent mass loss, reaching 60 percent for mass losses higher than 10 percent. MOE decreased with heat treatment the reduction was under 10 percent until 8 percent mass loss. The contact angle increased until 5 percent mass loss, decreasing slightly afterward. Heat treatment was shown to be a useful method to improve the technological quality of eucalypt wood as regards dimensional stability, allowing it to compete with higher-cost woods for some applications.
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