A New Extensional Mixing Element for Improved Dispersive Mixing in Twin-Screw Extrusion, Part 1: Design and Computational Validation

摘要

Twin-screw extruders (TSE) are typically the equipment of choice in polymer blending and compounding operations due to the relatively high stresses and controllable residence times they impart on the melts. However, the mixing action is shear dominated and shear flows are energetically inefficient for dispersive mixing by comparison with extensional flows. We present a new extensional mixing element (EME), developed as a static dispersive mixing element for TSEs with dispersive mixing provided by extension-dominated flow through stationary hyperbolically contracting channels. In Part 1 of the work, we present the design and show, experimentally and computationally, that the EME effectively imparts extension-dominated flow through its channels. We also show that the flow is fully developed throughout most of the EME sections, with only small inlet transients being observed, and that it is possible to predict the real pressure drop in the system. Experimental validation of the EME for immiscible blends of varying viscosity ratios will be discussed in Part 2.