Heating wood to improve performance dates back many thousands of years. This method results in increased decay resistance and improved dimensional stability to different degrees depending on the process used. Reductions in hygroscopicity, increased dimensional stability and decay resistance of heat treated wood depend on decomposition of a large portion of the hemicelluloses in the wood cell wall. In theory, these hemicelluloses are converted to small organic molecules, water and volatile furan-type intermediates. There is a strong connection between reducing the wood moisture content and decay resistance. As dimensional stability increases and hygroscopicity decreases, resistance to decay increases. A reduction in swelling over 40% results in no weight loss in a brown-rot decay test. However, strength properties are reduced in heat treated wood as a result of the degradation of the cell wall matrix due to the degradation of the hemicellulose polymer.
Keywords: heat treated wood, brown-rot fungus, equilibrium moisture content, weight loss, strength loss
Authors
Roger M. Rowell
University of Wisconsin, Madison, WI, USA
Guest Professor, EcoBuild, Stockholm, Sweden
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