High Speed Extrusion of Modified Polycarbonate

An important topic in the area of research and development in extrusion technology is to increase the economical efficiency. In general, an increase in mass flow rate is done by designing bigger machines, but this also increases costs for maintenance and batch changes. Another possibility to increase throughput is to use smooth barrel extruders with high screw speeds (from 2 m/s on). In further investigations several issues were detected in the field of high speed extrusion and the processing of polycarbonate. Because of the high shear sensitivity of this polymer, at higher screw speeds temperature increases massively. The reason for the lack of melting is the enthalpy of amorphous polymers. To handle this issue we decided to analyze the behavior of a modified polycarbonate with a high shear thinning range and the same zero viscosity as a typical extrusion material. In this essay, the manufacturing of a special blended polycarbonate is presented as well as first results of processing this material at high screw speeds. These investigations are based on the evaluation of various speed ranges on an extruder (D = 30 mm) with vacuum degassing and a direct torque drive. In addition, several pressure sensors along the axial screw length and a temperature sensor in the area of the screw tip were installed. With this arrangement, it is possible to make a statement on temperature homogeneity, pressure development and the melting process. The overall goal is to achieve optimization strategies for the high speed extrusion of polycarbonate.