Non‐Newtonian flow and the steady‐state shear compliance

Abstract

AbstractA survey of viscoelastic data on amorphous polymer melts indicates that the steady‐state shear compliance, Je, of many systems can be approximated from a knowledge of their flow response. For systems with monomodel molecular weight distributions, the absolute value of the reduced complex viscosity, η*/η0, is found to equal 0.67 ± 0.03 at the frequency ω, where ωη0Je = 1. This result applies to a variety of polymer systems and to a wide range of molecular weights and distributions as long as the highest molecular weight dispersion of the distribution constitutes more than 20 weight per cent of the sample. This relationship determines Je from non‐Newtonian flow data and thus provides a consistent way to relate differently shaped reduced variable curves and to calculate compliances from characteristic times reported in the literature. The connection between some commonly used times and Je is given. The method of calculating Je is successfully applied to capillary measurements of melt viscosities and to characteristic times determined from steady‐state shear measurements of concentrated polymer solutions.