Physicomechanical properties of Japanese cedar wood modified by high-temperature vapour-phase acetylation (HTVPA), a simultaneous acetylation and heat treatment modification process

Abstract

Wood modification can be broadly categorized into chemical and physical processes, with acetylation and heat treatment being two of the most common methods in each category, respectively. This study, for the first time, combines these two modification methods and investigates the effects of high-temperature vapour-phase acetylation (HTVPA) on the physicomechanical properties of Japanese cedar (Cryptomeria japonica) wood in the temperature range of 145 to 220 °C for 2 to 16 h. Additionally, the acetylation variations within the wood were evaluated. Attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and near infrared spectroscopy (NIR) spectral analysis showed that the hydroxyl group of Japanese cedar wood reacted with acetic anhydride to form an acetyl group by HTVPA process. When the HTVPA temperature was 220 °C, dehydration and deacetylation of wood occurred. Furthermore, based on the weight percent gain (WPG) and physicomechanical properties of the treated wood, the 200 °C/8h was considered the optimal HTVPA treatment condition. The profiling analysis results showed that the acetylation depth in the longitudinal direction was 40 mm, while the depth in the tangential and radial directions was 3–4 mm. However, the theoretical WPG of the surface of HTVPA treated Japanese cedar wood was 30.0–31.6 %.