A Devolatilization Model for a Screw Extruder with Multi-vent Sections

概要

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A devolatilization model for polymer melt in a multi-vent screw extruder has been proposed. In this model an overall film-interface geometry factor (OFIGF) comprised of local film-interface geometry factors (LFIGFs) is used as a measure of devloatilizing performance of a screw extruder. Moreover, the OFIGF is related to screw geometry, and opening angles of the open areas in vent sections and dependent on degree of filling or flowrate and screw speed. A solution was given how to calculate the film-interface areas and their exposure time in a venthole unfitted zone (VUfZ) without an open area and a venthole fitted zone (VFZ) with an open area for intermeshing co-rotation twin-screw extruders, and the OFIGFs for the two cases mentioned above were predicted under the conditions found in screw geometry and the opening angle of open area. The results suggested that devolatilizing performance of VFZ is lower than that of VUfZ due to the decrease in surface renewal effect, and a plot of ln{(wout-w*)/(win-w*)} against N1/2/Q does not strictly satisfy with a linear relationship in the general range of flowrate and screw speed owing to the dependencies of the OFIGF on them and those dependencies should be further considered for predicting the devolatilizing performance, and designing and scaling-up screw extruders.
一般社団法人プラスチック成形加工学会の論文