Numerical simulation of the transient flow of branched polymer melts through a planar contraction using the 'pom-pom' model

Calculations of the transient flow of branched polymer melts through a planar 4: 1 contraction and along a channel are presented. The polymer is modelled as a monodisperse suspension of 'pom-pom' molecules using the constitutive equation developed by McLeish and Larson [T.C.B. McLeish, R.G. Larson, J. Rheol. 42 (1998) 81-110], which provides a direct Link between the molecular topology and the flow properties of the melt. The branching produces an enhancement in the size of the upstream vortex, similar to that observed experimentally with branched polymer melts. The effect arises from the widely differing responses in shear and extensional flow, and is predicted to be sensitive to time, degree of branching and Weissenberg number. (C) 1999 Elsevier Science B.V. All rights reserved.