Changes in moisture exclusion efficiency and crystallinity of thermally modified wood with aging

This study aimed to investigate whether aging affects moisture exclusion efficiency and crystallinity of thermally modified wood. For this purpose, wood blocks of hornbeam (Carpinus betulus), Norway spruce (Picea abies) and oak (Quercus castanifolia), modified at 180 °C for 3 hours inside a ThermoWood kiln were exposed to a six-cycle artificial aging procedure. Aging reduced the efficiency and crystallinity of the modified woods. A significant negative correlation was found between the wood crystallinity and equilibrium moisture content (EMC) which indicates that change in the crystallinity index (CrI) measured by X-ray diffraction (XRD) affects the affinity of wood to moisture. The increased affinity of the modified wood to moisture after aging is probably due to the leaching of thermal degradation products as observed by Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) spectroscopy