Beschreibung:
<jats:title>Abstract</jats:title><jats:p>Many attempts to formulate viscoelastic constitutive equations (CEs) for polymeric liquids have resulted in a situation where as many as several tens of popular CEs are in competition nowadays. None of these can describe the available data for simple flows, consistently, and almost all of them display nonphysical instabilities in high Deborah number flows. This paper discusses the most important classes of viscoelastic CEs, present recent results on their stability, recommends some principles of choice of CEs for practical use, and highlights a certain class of CEs for the description of the available set of rheological data for the most well characterized polymers, while satisfying all the stability constraints.</jats:p>