An intrinsic route to melt fracture in polymer extrusion: a weakly nonlinear subcritical instability of viscoelastic Poiseuille flow

TL;DR

This paper identifies an intrinsic subcritical instability in viscoelastic Poiseuille flow that explains the onset of melt fracture during polymer extrusion, highlighting a fundamental limit related to elastic and viscous stress ratios.

Contribution

It provides the first weakly nonlinear analysis demonstrating a generic route to melt fracture via subcritical instability in viscoelastic flow.

Findings

Instability occurs at a fixed elastic-to-viscous stress ratio.

The analysis reveals a subcritical bifurcation leading to melt fracture.

Results suggest intrinsic flow limitations in polymer extrusion processes.

Abstract

As is well known, the extrusion rate of polymers from a cylindrical tube or slit (a ``die'') is in practice limited by the appearance of ``melt fracture'' instabilities which give rise to unwanted distortions or even fracture of the extrudate. We present the results of a weakly nonlinear analysis which gives evidence for an intrinsic generic route to melt fracture via a weakly nonlinear subcritical instability of viscoelastic Poiseuille flow. This instability and the onset of associated melt fracture phenomena appear at a fixed ratio of the elastic stresses to viscous stresses of the polymer solutionte