Effects of temperature and sulfonation on shear deformation of spruce wood

Summary The effects of temperature and sulfonation on the deformation of spruce wood at conditions comparable to those during screw press impregnation prior to mechanical pulping were studied using a dynamic testing method. In addition to the physical properties of wood, shear fracture surfaces obtained at different deformation temperatures and at different sulfonation levels were studied using scanning electron microscopy (SEM).The results showed that the failure energy of wood decreased gradually with increased deformation temperature in the tested range of 20–95 °C, due to thermal softening of the material. In addition to thermal treatment, the failure energy could also be reduced by sulfite treatment of the wood before deformation, and decreased with increasing sulfonation degree.The SEM analysis showed that increasing the deformation temperature causes the fracture plane to travel around the fiber walls instead of through them, thus exposing a smoother wood surface with less fiber damage. At a given deformation temperature, particularly at the lower temperatures, sulfonation improves fiber separation.Financial support from the Swedish National Board for Industrial and Technical Development (NUTEK) is gratefully acknowledged