TWIN SCREW EXTRUSION DEVOLATILIZATION - FROM FOAM TO BUBBLE FREE MASS-TRANSFER

The present research program, based upon the experimental performance of a 20 mm counter‐rotating, non‐intermeshing twin screw devolatilizer with several polymer/solvent systems has developed theoretical approaches to modeling both the bubble growth dominated mass transfer regime as well as the essentially bubble free regime (1, 2). This work encompasses the area of transition from the bubbling to the non‐bubbling areas. This transition to some degree, probably exists in nearly all real devolatilization processes. The work combines a foam simulation model, which integrates elementary bubble processes, with the mass transfer from single phase liquid films through a penetration theory based model. The modeling is successful at correlating the experimental data and shows realistic effects with regard to residence time, surface area, and average mass transfer coefficient as functions of vent loading. Copyright © 1990 Society of Plastics Engineers