Thermal Treatment of Poplar Hemicelluloses at 180 to 220 °C under Nitrogen Atmosphere

Hemicelluloses were separated from poplar wood and exposed to thermal treatment. Changes in chemical content were investigated from 180 °C to 220 °C in a nitrogen atmosphere. Fourier transform infrared spectroscopy, X-ray diffraction, and differential thermal gravimetric analysis were used to characterize the hemicellulose before and after the thermal treatment. The effects of temperature on hygroscopicity and color were measured. The results showed that hemicelluloses were sensitive to temperature. β-glucosidic bonds and side chains in hemicelluloses were cleaved around 180 °C, and the increased temperature promoted the breaking process. Esterification reactions happened during the treatment. When the treatment temperature reached 220 °C, all side chains broke down, and partial carbonization occurred. Therefore, the color became darker, and the hydrophobicity increased. This study could help to explain the changes in wood that occur during thermal treatment.