A mechanism for extrusion instabilities in polymer melts

M. Fyrillas, G. Georgiou, D. Vlassopoulos, S. Hatzikriakos

Research output: Contribution to journalArticleAcademic

11 Citations (Scopus)


A mechanism for explaining some of the instabilities observed during the extrusion of polymer melts is further explored. This is based on the combination of non-monotonic slip and elasticity, which permits the existence of periodic solutions in viscometric flows. The time-dependent, incompressible, one-dimensional plane Poiseuille flow of an Oldroyd-B fluid with slip along the wall is studied using a non-monotonic slip equation relating the shear stress to the velocity at the wall. The stability of the steady-state solutions to one-dimensional perturbations at fixed volumetric flow rateis analyzed by means of a linear stability analysis and finite element calculations. Self-sustained periodic oscillations of the pressure gradient are obtained when an unstable steady-state is perturbed, in direct analogy with experimental observations.
Original languageEnglish
Pages (from-to)2498-2504
JournalPolymer engineering and science
Issue number12
Publication statusPublished - 1999


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