MOKUZAI HOZON (Wood Protection)

Effects of heat treatment in N₂ gas on bending strength and fungal resistance properties of Styrax tonkinensis have been examined. Heat treatments show the positive effect on the resistance to both types of fungi (white-rot and brown-rot) at 200°C and for more than 8 hours. However, heat treat-ment at the above conditions decreases its strength to as much as 40 %. The decrease of hemicel-lulose is thought to contribute to the durability improvements.

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In late years, several heat-treated woods which have high durability against wood decay fungi without chemicals are imported by Japanese business firms. Plato-treated wood is one of these products.
It was reported that the Plato-treated wood appealed high resistance against wood decay fungi such as Coniophora puteana (Schumacher ex Fr.) Karsten and Coriolus versicolor (L.) Quelet from the result of a modified EN 113 decay test method. In the paper, however, percentage mass losses of controls (untreated wood samples) are not large enough to obtain these conclusions especially against C. versicolor. So, Japanese consumers would like to know whether this treated wood has the same durability as preservative-treated wood. Therefore, we evaluated the decay and termite resistances of Plato-treated wood.
The result of JIS Z 2101 decay test showed that Plato heat-treatment reduced mass losses by white and brown rot fungi. Even the smallest mass loss percentage on treated-Douglas fir showed 10.0% by Trametes versicolor (L.: Fr.) without a weathering process. We concluded that Plato heat-treatment didn't give the substantial durability. Some species of Plato-treated wood showed more mass losses by termite feedings compared to untreated wood in a laboratory scale test.

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