Abstract
In this study, decay durability of heat-treated wood produced in supercritical carbon dioxide was investigated. Specimens were prepared from sugi heartwood for soil-buried test and sugi sapwood for fungal resistance test. The specimens were conditioned at 0% or 11% moisture contents and heated in supercritical carbon dioxide. The heat-treated specimens were buried in soil for 5 years at two test sites in Japan, and their weight loss was measured. The weight loss resulting from decay decreased with increasing treatment temperature and specimen moisture content. The results suggest that decay durability improved owing to the high treatment temperature and moisture content that accelerated the thermolysis of wood components leading to low equilibrium moisture content. From fungal resistance test, results showed that the wood specimens heat-treated in supercritical carbon dioxide featured higher decay durability compared with those treated in steam or nitrogen gas at atmospheric pressure. Heat treatment in supercritical carbon dioxide is performed under high temperature and pressure condition, and high reactivity of the water molecules in the specimen might be induced to accelerate the thermolysis of wood components.
