The effects of temperature and sulfonation on the deformation of spruc
e wood at conditions comparable to those during screw press impregnati
on prior to mechanical pulping were studied using a dynamic testing me
thod. In addition to the physical properties of wood, shear fracture s
urfaces obtained at different deformation temperatures and at differen
t sulfonation levels were studied using scanning electron microscopy (
SEM). The results showed that the failure energy of wood decreased gra
dually with increased deformation temperature in the tested range of 2
0-95 degrees C, due to thermal softening of the material. In addition
to thermal treatment, the failure energy could also be reduced by sulf
ite treatment of the wood before deformation, and decreased with incre
asing 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 su
rface with less fiber damage. At a given deformation temperature, part
icularly at the lower temperatures, sulfonation improves fiber separat
ion.