Origin of the Sharkskin Instability: Nonlinear Dynamics

The appearance of surface distortions on polymer melt extrudates, often referred to as sharkskin instability, is a long-standing problem. We report results of a simple physical model, which link the inception of surface defects with intense stretch of polymer chains and subsequent recoil at the regi...

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Bibliographic Details
Published in:	Physical review letters 2021-08, Vol.127 (8), p.1-088001, Article 088001
Main Authors:	Varchanis, Stylianos, Pettas, Dionisis, Dimakopoulos, Yannis, Tsamopoulos, John
Format:	Article
Language:	eng
Subjects:	Computational fluid dynamics Creep (materials) Dynamic stability Extrusion Extrusions Hopf bifurcation Nonlinear dynamics Orange peel Period doubling Polymer melts Polymers Surface defects Surface distortion Surface stability
Online Access:	Get full text
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Summary:	The appearance of surface distortions on polymer melt extrudates, often referred to as sharkskin instability, is a long-standing problem. We report results of a simple physical model, which link the inception of surface defects with intense stretch of polymer chains and subsequent recoil at the region where the melt detaches from the solid wall of the die. The transition from smooth to wavy extrudate is attributed to a Hopf bifurcation, followed by a sequence of period doubling bifurcations, which eventually lead to elastic turbulence under creeping flow. The predicted flow profiles exhibit all the characteristics of the experimentally observed surface defects during polymer melt extrusion.
ISSN:	0031-9007 1079-7114