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The torque in the metering zone of single screw extruders
Author(s) -
Mennig G.
Publication year - 1987
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.760270302
Subject(s) - metering mode , drag , plastics extrusion , pressure gradient , flow (mathematics) , mechanics , materials science , conical surface , dissipation , torque , mechanical engineering , thermodynamics , engineering , composite material , physics
To study the energy dissipation in the different zones of an extruder, a special barrel has been designed where local torques T q can be measured at the beginning of the conveying, the transition, and the metering zone. Experiments carried out for a commercial polyethylene and poly(vinyl chloride) at different processing conditions show that in some cases negative T q in the metering zone may occur. A very basic analytical treatment of the flow situation in the metering zone shows that for a given drag flow T q is dependent on the pressure gradient and particularly on its sign. T q decreases with decreasing positive pressure gradient until there is pure drag flow. It further decreases with increasing negative pressure gradient until it becomes zero and even negative. A comparison of theoretical and experimental results for the metering zone shows good quantitative agreement though the main aim of the paper is to provide a better general understanding of the complex situations inside an extruder.