Steady flow simulation of a polymer‐diluent solution through an abrupt axisymmetric contraction using internally consistent rheological scaling

Abstract

AbstractIn this work, a new methodology is developed that describes the viscoelastic scaling of a polymer‐physical foaming agent (PFA) solution in a detailed and internally consistent manner. The approach is new in that while previous researchers have largely focused on scaling down experimentally obtained high pressure polymer‐PFA solution viscosity data onto a master curve for the viscosity of the undiluted polymer melt at a reference temperature and atmospheric pressure, we have generated the shear viscosity data required for our simulations by systematically scaling up the viscosity values obtained from measurements on a pure polymer melt to the desired temperature, pressure, and concentration values characterizing the flow. Simulations have been run for the flow of a polymer‐PFA solution through an extrusion foaming die with an abrupt axisymmetric contraction and good qualitative agreement is obtained with experimental pressure drop measurements obtained previously in our laboratory. The pressure drop rates and temperature rise rates have been estimated at the surface of incipient nucleation. Because of the short residence times in the die for the microcellular foaming process, approximating the flow through the die as a single phase flow in our simulations still gives useful insights into the dynamics of the flow. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007