ETH Polymer Physics seminar


2003 -01 -22
10 :15 at ML J 21

Modified constraint release: Are uniaxial flows more critical for the validation of molecular based model that shear flows?

Jan van Meerveld

Polymer Physics, Institute of Polymers, ETH

In a recent investigation of molecular based rheological models are compared with experimental results on concentrated PS solutions, number of entanglements ranges from 7 to 25, in stationary and transient extensional flows. The main conclusion is that >the steady state extensional viscosty are lower than the data in all cases and are lower by large amounts depending on the strain rate that is chosen<. Inspired by chain connectivity it is motivated that convective constraint release should decrease with increasing orientational order of the system. This improves the disagreement between experiments and current molecular based model uniaxial flows. Moreover it is shown that the predictions in shear and biaxial flows is rather insensitive to the formulation of convective constraint release.


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