Molecular physics of a polymer engineering instability: Experiments and computation

Hassell D. G. , Mackley M. R. , Sahin M. , Wilson H. J. , Harlen O. G. , McLeish T. C. B.

PHYSICAL REVIEW E, cilt.77, sa.5, 2008 (SCI İndekslerine Giren Dergi) identifier identifier


Entangled polymer melts exhibit a variety of flow instabilities that limit production rates in industrial applications. We present both experimental and computational findings, using flow of monodisperse linear polystyrenes in a contraction-expansion geometry, which illustrate the formation and development of one such flow instability. This viscoelastic disturbance is observed at the slit outlet and subsequently produces large-scale fluid motions upstream. A numerical linear stability study using the molecular structure based Rolie-Poly model confirms the instability and identifies important parameters within the model, which gives physical insight into the underlying mechanism. Chain stretch was found to play a critical role in the instability mechanism, which partially explains the effectiveness of introducing a low-molecular weight tail into a polymer blend to increase its processability.