Chemical characteristics and viscoelastic properties of Nothofagus alpina thinning wood thermally modified using a dynamic mechanical analysis (DMA)

This study investigated variations in the chemical characteristics and viscoelastic properties of Nothofagus alpina wood from thinning during a thermal modification. In order to study the viscoelastic properties during an in-situ thermal modification process, a dynamic mechanical analysis apparatus was used. The initial moisture content of wood, modification temperature and the heating rate to reach the modification temperature were used as variables to assess their effect on viscoelastic properties. Furthermore, changes in the chemical characteristics before and after the simulated thermal modification process were analyzed by FTIR. The results underlined the importance of water content in wood, as it influenced the chemical characteristics of the modified wood in relation to the initial moisture content, and the changes of viscoelasticity in the variation of the storage modulus (E ') and loss modulus (E ''), with E '' being more sensitive to the higher humidity used in this study. The modification temperature conditioned the effect of the moisture content, with a second additional peak being observed in E '' and tan delta (damping factor) at the modification of 210 degrees C and 12% moisture content, but not in the oven-dry samples. Additionally, the effect of the heating rate was more pronounced at the lower modification temperature.