Thermal Modification Benefits Wood

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Thermal modification of wood involves gradually heating it in a chamber – completely devoid of oxygen to prevent combustion – between 410-450 degrees (F). The process alters the wood on a cellular level, providing a number of benefits and giving the wood a pleasant brown color.

Thermally Modified Timber (TMT) has increased dimensional stability, ranging from 30-80 percent. The wood will work less or change dimensions less under the influence of air-borne humidity. Because the wood moves less, surface protection appearance is improved.

Equilibrium moisture content is reduced by 50 percent. In addition, TMT has increased resistance to wood-destroying fungi and insects without the need for chemical treating. The protective qualities permeate all the way through the wood. TMT also has improved heat insulation.

There are disadvantages of the thermal modification process, making the wood unsuitable for some applications. For example, TMT is more brittle, and screw holes should be pre-bored. Impact strength is reduced 30-50 percent, so TMT should not be used for load-bearing construction.

TMT is used in various construction applications in Europe. For example, it is used for cladding and siding, replacing chemically treated wood, and decking, similarly replacing chemically treated wood as well as tropical woods. Is also used in joinery wood, notably in windows because of its improved insulation quality, and also plywood.

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American Wood Technology’s improved Moldrup hydro-thermal process works with air pressure and pure wood moisture vapor pressure. It is 2-7 times faster than conventional processes for the actual treatment phase of the process. Temperatures are 20-30 degrees (Celsius) lower than conventional processes. The technology also collects acids, volatile organic compounds and degeneration chemicals without emissions to the environment.

Limited steam overpressure to reduce acidity of the modified wood limits corrosion, glueing and coating issues. The process also prevents the wood moisture from dropping to less than 3-4 percent, meeting the required equilibrium moisture content.

The technology involves simple plant equipment with a low investment per board foot; annual capacity is based on experience from industrial plant use since 1999.

For more information, contact American Wood Technology at (877) 785-0274, email or visit