Experimental in-situ viscosity measurement of polymer melts in a film extrusion die

Abstract

In the present work, we employ an extrusion die as a viscometer to directly measure in-situ viscosity behaviors by measuring pressure drop and flow rate. The shear rate was properly scaled with flow rate, and the viscosity was again scaled with the ratio of pressure drop to flow rate. The scaling was achieved by the energy-dissipation based flow modeling method [Jang and Hwang, J. Non-Newt. Fluid, vol. 253, p.7–15], which extends the Metzner-Otto correlation to pressure-driven flows. We investigated polymeric flows in a slit die with three different polyethylene melts using experimental data in the literature. Additionally, two different polymeric flows inside complicated film dies were experimentally tested: (i) in a lab-scale film die with four different concentrations of dilute polymer solutions, and (ii) polymer melt flows through a film extrusion die with three polymer melts. The relative error between experimental and theoretical effective viscosity estimation appears less than 14 %. © 2024 Elsevier Ltd