Effect of Vapor-Phase Surface Acetylation of Japanese Cedar Wood on Fungal Degradation and Dimensional Stability

Vapor-phase acetylation of heartwood in Japanese cedar wood (<i>Cryptomeria japonica</i> D. Don) was carried out as a surface acetylation method to elucidate the relationship between the depth of acetylated area and fungal decay resistance. The acetylated wood (VPAW), prepared with acetic anhydride vapor by heating at 80°C for 72 h, indicated a significant fungal decay resistance and dimensional stability in water-soaking test, similar to liquid-phase acetylated wood (LPAW). The VPAW provided more than 15% of the weight percent gain (WPG) up to a depth of 7 mm from the wood surface, while LPAW gave ∼20% WPG uniformly throughout the wood. However, 24-h vapor-phase acetylation, giving 15% WPG at a depth of 0–2 mm, showed insufficient fungal decay resistance. These results showed that at least 7 mm thickness of the acetylated region with 15% WPG was required to suppress the fungal decay of acetylated wood under laboratory conditions.