Thermal-softening properties of water-swollen wood: The relaxation processdue to water soluble polysaccharides

To clarify the thermal-softening properties of water-swollen wood, the visc oelastic properties of wood specimens conditioned to various moisture conte nts and of water solutions of amorphous cellulose, hemicellulose and milled wood lignin, have been studied in the temperature range from -150 to 0 deg reesC at frequencies ranging between 0.5 and 10 Hz. A relaxation process ar ound -40 degreesC was observed in wood specimen with high moisture content. It was observed in wood specimens with lower moisture content at higher te mperature. The value of apparent activation energy for the relaxation proce ss was 50 kJ/mol. On the other hand, a similar relaxation process was obser ved in water solutions of amorphous cellulose and hemicellulose around -40 degreesC, but it was not observed in water or water solution of milled wood lignin. The values of apparent activation energy for the relaxation proces s were 230-545 kJ/mol. Therefore, we considered that the relaxation process was due to the water-swollen polysaccharides and affected by the situation s of water molecules. (C) 2001 Kluwer Academic Publishers.