3.2.2. Single Screw Extrusion. For single-screw extrusion,
only two processing parameters need to be studied: screw
rotation speed and barrel temperature profile. Screw rotation
speeds ranging from 10 to 120 rpm were compared, with the
best expansion being obtained at 50 rpm corresponding to a
torque between 30 and 40 Nm.
The barrel temperature profile was similar to the previous
one used for the twin-screw extrusion (heating zone 1:
30
◦
C; die: 160
◦
C). A heterogeneous material was obtained
with nonmelted granules within low expanded foam.
Increasing the temperature of the feeding zone (Tabl e 5)
leads to a foam similar to the one produced by twin-screw
extrusion.