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A mechanism for extrusion instabilities in polymer melts
Author(s) -
Fyrillas M.,
Georgiou G.,
Vlassopoulos D.,
Hatzikiriakos S.
Publication year - 1999
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.11637
Subject(s) - extrusion , materials science , mechanism (biology) , polymer , composite material , polymer science , epistemology , philosophy
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.