A Thorough Examination of a Torsional Dynamic Rheometer with a Closed Oscillating Cavity

Abstract

The so-called Rubber Process Analyser, RPA 2000®, is a torsional dynamic rheometer, whose test cavity design is similar to that of the Moving Die Rheometer, a well known rotorless vulcameter, and the only available device which offers the possibility to test very stiff materials, in dynamic conditions. The paper systematically investigates the test conditions prevailing in the instrument, with respect to basic rheology principles, in order to identify the possible sources of errors and to quantify them. Using a monodisperse polymer melt, an experimental comparison is made with conventional cone-and-plan rheometers and data obtained with the RPA are found similar. A numerical simulation of the instrument test cavity is made in order to evaluate the error associated with the closed rim and the associate pressurisation. Results obtained show that rheological functions can be evaluated with a confidence of around 10%.