With the standard screw configuration, the system was unable
to maintain a steady-state process as the large mixing zones, with
higher temperatures, retarded the material movement, thus allowing
most of the ethanol in the mixture to be vaporized and move
backward along the barrel and escape through the feeding hopper.
This volatile ethanol might generate unstable pressures at the
injection port that led to fluctuations in the liquid ethanol flow.
For this reason, the modified screw configuration was designed
with two small mixing zones at the very beginning to aid in the
homogenization of the formulation components (Fig. 2). Additionally,
reversing elements were incorporated into the second mixing
zone to facilitate a melt seal, which prevented any gaseous ethanol
from traveling backward along the barrel and exiting through the
feeding hopper.