Numerical simulation of the fluid dynamics and morphology of a polymeric blend in a twin-screw extruder

Abstract The blending of homopolymers is commonly used to create polymeric materials with synergistic properties. Most polymer blends are immiscible, consequently they have a multiphase structure, conferring them highly tunable properties. The twin-screw extruder is the most common device used for polymer compounding. In this work, the evolution of a disperse polymer blend morphology in a twin-screw extruder is studied by numerical simulations. The fluid dynamics of the blend, treated as a pseudo-homogeneous Newtonian fluid, is solved by the finite element method under quasi-steady and isothermal conditions. The velocity gradient obtained along several trajectories of the flow field is used as input in a previously developed model able to predict the blend morphology. The history of deformation of the droplets and their topological changes in terms of evolution of the stretch ratio and the unstretched droplet radius are investigated. The average blend morphology is computed for a population of droplets, highlighting the effect of the screw rotation speed and the blend viscosity ratio.