also, throughput and screw "speed, wliiuli'(-1" be changed (hiring
extmsion, considerably alter vetocity distrit'ution; thereby, more
uniform shear stresses can be tchjcvcd, with consequent better ma-
terial horn oge" city.
f;urthemiort, in coun terra tat ing screws, the material forceti into
the calcndering gap untlcrgoes, as it has been nncntioned before, a
high shear but only a small fraction of the chamber's volume passes
through it. This adds to the nonhomogcneity of the cxtrudate. Mix-
ing devices as interrupted flights, etc., will arncliorate the results,
although only partially.
In corotating screw systems, the very presence of the area restric-
tion and stiapo cliange in the pasMge between screws further en lianccs
homogeneily without localized high shear at any poirft.