More often than not, extrusion operators do not critique the barrel zone temperatures to the resin when being processed when using a barrier type extrusion screw. Typically, it is not uncommon to see the extruder barrel zones set at temperatures lower than the desired melt temperature. When this type of operating condition is used, the control of the extrudate temperature is totally dependent to the screw geometry and the viscous heat it develops from the shear rates that are generated by the channel depths, flight clearances and screw speed.
By studying the heater zone layout and how they are located in reference to the different sections of the screw this will help determine the proper zone setting. This paper will first give the reasoning of the process, based on the general configuration shown above, then suggested zone settings for the resin listed above will be recommended.
The feed throat section should be set to a temperature where it is "warm to the touch", which is somewhere between 110°F and 120°F.