Abstract
The performance and capabilities of parallel and conical twin screw extruders are compared and contrasted. In particular, the processing behaviour of both systems is explored in the light of the extrusion requirements for specific PVC end-use applications including pipe, profiles, pelletising and sheet. System configuration, residence time and shear are reviewed, and overall performance is assessed using the Master Graph approach of Schuler. It is concluded that, although parallel extruders will continue to dominate the high performance market segment for the foreseeable future, conical extruders have great potential for development because of their processing flexibility. Provided increased screw speed does not have severe effects on wear rates, significant gains in output rate are possible which could lead to conical extruders becoming fully competitive with parallel systems.
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