Hassager, Ole

Jensen, Mette

Marin, Jose

Rasmussen, Henrik K.

Yu, Kaijia

Polymer extensional flow is the one of the most important deformation in polymer processing. It is the dominant deformation in melt-spinning, bottle-blowing, and roll-coating. Because the molecular structure of the polymeric system strongly influences the extension viscosity, extensional flow measurements are useful for polymer characterization. The Sentmanat extensional Rheometer[1] is an new testing platform for the study of polymers and elastomers in extensional flow. This technique employs a dual wind-up drum technique to perform an uni-axial extensional deformation during experiments. This miniature unit requires small amount of material and has been designed in such a manner that it can be used for polymer melt and soft elastomers characterization over a very wide range of temperatures and kinematic deformations and rates. In order to validate the reliability of this testing platform a finite element technique based on a Lagrangian kinematics description of the 3D time-dependent flow of K-BKZ type fluids [2] is used to simulate extension flow of both cylindrical and strip shaped sample in the SER. Here the purpose is to discuss the potential deviations from ideal uni-axial deformation, based on theoretical ideal configurations. Our simulation can setup a theoretical based 'safe' geometry range of samples for SER experiments. Furthermore, the simulations are able to capture flow instabilities in stress relaxation, which have been experimentally observed [4]. References: [1] M.L. Sentmanat, Rheol Acta, 43:657--669, 2004. [2] J.M.R. Marín, H.K.Rasmussen, J. Non-Newtonian Fluid Mech, 156 (3) , p. 177-188. [3] K.Y, J.M.R. Marín, H.K.Rasmussen, O.Hassager, J. Non-Newtonian Fluid Mech, 165 (1) , p. 14-23. [4] Y.Wang, P.Boukany, S.Wang, X.Wang, Physical Review Letters, 99, 237801 (2007). *The title of this submission has been modified to remove the name of a commercial product or company to bring the title into compliance with SOR policy

Modeling of dual cylinder wind-up extensional rheometers

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