Extrusion Flow of Polymer Blends with Droplet Morphology
Laboratory of Food Process Engineering,
E. T. H. Zurich,
CH-8092
The thermodynamically consistent blend model of Dressler and Edwards [1] has been solved computationally to understand the flow of polymer blends with droplet morphology in the metering section of a single screw extruder. Extending the method proposed in Dressler and Edwards [2] to non-symmetric flow fields, the dynamic model has been solved for a mixed Couette/Poiseuille flow as encountered in the metering section of a single screw extruder. In our code we consider both the mixing flow perpendicular to the flights of the extruder and the conveying flow parallel to the flights. We have performed calculations for different model (e. g. blend component viscosity ratio) and flow geometry parameters (e. g. helix angle of the extruder screw) to understand qualitatively microstructure-rheology relationships for polymer blends in extrusion flows. Macroscopic flow characteristics such as the volumetric throughput, the residence time distribution function, and the non-Newtonian flow stresses are discussed along with microscopic characteristics of the blend such as oblate/prolate configurations of the droplets, break-up/coalescence rates, and matrix microstructural characteristics.
[1] Dressler, M. and
Edwards, B. J. (2004). Rheology of polymer blends with matrix- hase viscoelasticity and a narrow
droplet size distribution. J. Non-Newtonian Fluid Mech., 120:189,205.
[2] Dressler, M. and Edwards, B. J. (2005). A
method for calculating rheological and morphological properties of
constant-volume polymer blend models in inhomogeneous shear fields. J. Non-Newtoian Fluid Mech., 130:77,95.