Evaluation of parallel plate type rheometer using an oscillatory viscoelastic flow simulation

Abstract

The specimen of a polymer melt in a rotational-type rheometer protrudes from the jigs when we measure the rheological characteristics of polymer melts by use of rotational-type rheometers. To clarify the effect of this protruding part size on the estimated rheological characteristics in the oscillatory flow, we tried to estimate the storage modulus G' and loss modulus G" using the viscoelastic flow simulation results in the parallel plate rheometer by the finite element method. The multiple mode Phan-Thien Tanner (PTT) model was employed as the constitutive equation. The estimated G' and G″ increase with the protruding part size at the same frequency. The phase difference δ and the amplitude of shear stress τ0 need for the estimation of G' and G". The d was almost independent of the protruding part size. While, the τ0 increased with the protruding part size because of shear stress rise near the edge of the jigs in case of large protruding part size. The absolute deviations of the estimated G' and G″ using the simulation results were up to 20 % at the protruding part size of 1 mm when the plate radius is 12.5 mm and the distance between the plates is 2 mm. © 2009 The Society of Rheology, Japan.