First insight into the high speed extrusion of polycarbonate

Increasing the economical efficiency of single screw extrusion is an important factor in the area of research and development in extrusion technology. Enlarging processing machines is an approach which raises the mass flow rate but at the same time increases costs for maintenance or batch changes. This is why the focus of this essay lays on an increasing speed at a constant diameter, in order to improve the output. Investigations with polyolefins show that in terms of high-speed extrusion (from 2m/s on) particular attention has to be paid on the partially poor feed behavior and high processing temperatures. Based on the results of previous studies, the investigation of amorphous thermoplastics (polycarbonate) in combination with high-speed extruders is promoted at the KTP institute. Due to the different molecular structure from amorphous to partially crystalline (polyolefin) it can be assumed that the state of knowledge in areas of feed behavior, temperature development or mixing homogeneity can be transferred only partially. The reason for the lack of melting is the enthalpy of amorphous polymers. This essay introduces the first observations of temperature homogeneity and pressure development partially at high-speed extrusion with polycarbonate. These observations are based on the evaluation of various speed ranges on an extruder (D = 30 mm) with vacuum degassing and torque direct drive. The measurements occur with a temperature sensor in the area of the screw tip and with several pressure sensors along the axial screw length. This arrangement allows making a statement about temperature homogeneity, pressure development and the melting process. Based on these results, approaches to process optimization are introduced.