Rheometry in uniaxial elongation
Non-linear Viscoelasticity of Polymer Melts

Elongation measurements on polymer melts present a number of difficulties. In particular, given the thinning of the sample cross-section and the resulting low forces, stationary flow regimes are very rarely reached by direct methods; thus, most results are obtained under transient conditions. The difficulty of direct measurements has led to the development of techniques for measuring parameters qualitatively related to elongation behavior (indirect methods).