MODIFICATIONS IN SPRUCE WOOD STRUCTURE FOLLOWING HYDRO-THERMAL TREATMENT EVALUATED BY NIR SPECTROSCOPY.

Sitka spruce wood samples were subjected to different conditions of hydrothermal treatment at 140°C by varying the relative humidity and period of exposure. The control/reference and treated wood samples were evaluated using near infrared spectroscopy (NIRS), principal component analysis (PCA) and two dimensional correlation spectroscopy (2DCOS) in order to identify the structural modifications appearing during the treatment. Following this, the changes were reflected by the shifting of the bands position, modifications in bands intensities and width, as well as baseline offset. Higher modifications were identified in the 7400-6000 and 5100-4100 cm-1 regions assigned mainly to hemicelluloses and extractives, indicating that these components were the most susceptible to degradation in the present treatment conditions. Further, by PCA was possible to differentiate the modifications in the wood samples according to the time of treatment and relative humidity, while by 2DCOS was possible to identify the sequential order of modifications. [ABSTRACT FROM AUTHOR]