Extensional response of the pom-pom model through planar contraction flows for branched polymer melts

One objective of this study is to assess the influence of the number of dangling arms at each end of the pom-pom molecule on flow characteristics in a 4:1 planar rounded-corner contraction, where varying the number of arms affects the level of entanglement in the system. For these complex flows, we evaluate the major influence of extensional viscosity and Trouton ratio when comparing kinetic-based as opposed to phenomenological network-based models. The stability of the proposed extended pom-pom model (XPP) is investigated for a range of Weissenberg numbers utilising a hybrid finite-element/volume scheme. For this scheme, we solve the momentum-continuity equations by a fractional-staged Taylor–Galerkin/pressure-correction procedure and invoke a cell-vertex fluctuation distribution finite volume scheme for the constitutive law. Distinction may be drawn between fluid response in the extension-hardening regime and those displaying a degree of softening. In particular, trends in salient-corner vortex-intensity response can be associated with the extensional properties of the extended version of the pom-pom model. Critical levels of solution elasticity attainable depend on precise extensional viscosity characteristics. The influence of various model parameters upon field response is described through rates of deformation, stress and stretch. This would include consideration for parameters governing anisotropy (αα), and the ratio of stretch to orientation relaxation times (ɛɛ).