Ermittlung von Materialkennwerten von Kunststoffschüttgütern und Simulation der Vorgänge im Einzugsbereich von konventionellen Einschneckenextrudern
Mathematical simulations are already frequently used for the design of single-screw extruders for plastics processing and have the advantage of saving not only time and personnel, but are also economical. In order to obtain simulation results for the feed section of single-screw extruders with a good accuracy, not only the friction coefficients but also the pressure coefficients (the quotient of radial and axial pressure) of plastic bulk materials must be determined. It is of great importance that the determination of these material indices is based on the real conditions of the extrusion process. With this background in mind, available measurement devices for the determination of pressure coefficients, coefficients of friction, and density of plastic bulk materials were used to set boundary conditions for calculations in this work. A measurement device was then developed, which determines the material indices of the plastic bulk materials in the dynamic state. Measurements on several plastic bulk materials show that with rising axial pressure the product of coefficient of friction and pressure coefficient decreases. On the other hand this product rises for all examined plastic bulk materials with increasing velocity. The influence of temperature on the product of coefficient of friction and pressure coefficient is substantially more complex. The dependence of the friction characteristics and the plastic bulk density on temperature, axial pressure, and velocity are determined by means of a statistical testing plan and a regression analysis, and can be quantified by a regression equation. The regression equations are used in a model, which describes the processes in the feed section of single-screw extruders in two dimensions.
info:eu-repo/classification/ddc/660, Technische Chemie, Einschneckenextruder, Kunststoff, Schüttgut, Verarbeitungseigenschaft, Stoffwert
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