AUTHORS: Grigory Pyshnograi, Darina Merzlikina, Petr Filip, Radek Pivokonsky

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ABSTRACT: The Vinogradov and Pokrovskii rheological model was extended for a description of rheological behaviour of branched polymer melts. Since stationary elongational viscosity is a nonmonotonic function of the elongational rate, it required a generalization of the law of internal friction for beads of macromolecule. To achieve high prediction accuracy was proposed multi-mode approximation. The contribution of each independent mode to a stress tensor corresponds to the individual polymer fractions differing in relaxation time and viscosity. The theoretical predictions of the generalized model provide a good agreement with the measured steady and transient rheological characteristics of two samples branched low density polyethylenes.

KEYWORDS: Constitutive equations, Mesoscopic approach, Polymer dynamics, Polymer melts, Viscometric flows, Viscoelasticity

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