The response of pulp fibers to mechanical treatment imparted during me
dium-consistency fluidization has been investigated as a function of f
iber morphology. Fluidization beats and induces curl and microcompress
ion in the fibers. The pulp freeness decreases, and the sheet stretch
per unit tensile strength increases as the treatment energy increases.
This change is observed irrespective of fiber morphology. Thicker-wal
led fibers are more microcompressed by this treatment than thinner-wal
led fibers.