Page 31 - Plastics News April 2020

Other Factors That Impact Melt Temperature the screw.
The screw design in the melting zone directly impacts Often overlooked, pressure generation at the discharge
the melt temperature, and is significant. Temperature of the TSE also adds to the melt temperature. The more
setpoints in this zone will also contribute to the melt restrictive the front end, the higher the pressure and
temperature. Perhaps counter-intuitively, higher corresponding melt temperature.
setpoints generally result in a lower melt temperature.
Accordingly, in this study a reverse temperature profile The point is that the front-end design must be
(higher temperature setting in the first part of the considered when managing melt temperature in a
process) was selected to lessen the melt-temperature corotating twin-screw extruder.
rise associated with the melting zone. An optimized melt With corotating TSEs, screw design, front-end
zone is a good start. configuration, temperature settings and operating
conditions all impact what the formulation
In addition to melting, it is apparent that the screw must
also be designed to melt and mix without excessive shear “experiences” in the TSE process section and directly
inducement. The use of wide kneading blocks and influences the properties of the final part. Managing
melt temperature and minimizing degradation is key to
reverse elements for mixing will result in more energy
being imparted to the process and further raise the melt making high-quality parts and must be managed to
temperature, and must be considered when designing achieve optimization of any polymer process.

APRIL 2020 28 Plastics News