Abstract
Earlier studies have indicated that consequential amounts of air can be incorporated into concentrated suspensions during their processing. In this study the effects of air entrainment on the rheological behavior and extrudability of two concentrated suspensions with 57 and 63% volume of solids were investigated. The air content was altered by the imposition of vacuum in a twin screw extruder. The rheological behavior of the suspensions was characterized by employing steady torsional flow in a Rheometrics System IV in conjunction with a flow visualization technique for the characterization of the yield stress, shear viscosity and wall slip behavior of the suspensions. The removal of air from the suspension was indeed found to modify the theological behavior and extrudability of the suspension. Furthermore, it was demonstrated that when the solid concentration approaches the maximum packing fraction the sudden decrease of the air concentration of the suspension results in severe instabilities which are manifested by results in significant oscillations in operating parameters during twin screw extrusion processing.
Original language | English |
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Pages (from-to) | 201-210 |
Number of pages | 10 |
Journal | Plastics, Rubber and Composites Processing and Applications |
Volume | 24 |
Issue number | 4 |
State | Published - 1995 |