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The sharkskin instability of polymer melt flows
1Department of Chemical Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706-1691.
Chaos (Woodbury, N.Y.)
|June 5, 2003
Summary
Polymer melt flow instabilities, like sharkskin, stem from elastic properties and wall interactions. Understanding polymer-wall slip and disentanglement is key to predicting and controlling these extrusion defects.
Area of Science:
- Rheology
- Polymer Physics
- Fluid Dynamics
Background:
- Polymeric liquids exhibit flow instabilities distinct from Newtonian fluids due to elasticity.
- The sharkskin phenomenon is a common extrusion instability in linear polymers.
Purpose of the Study:
- To review recent studies on the sharkskin instability in polymer extrusion.
- To highlight the role of polymer-wall interactions and slip.
Main Methods:
- Summary of key experimental observations.
- Review of recent theoretical developments on slip and disentanglement.
- Analysis of viscoelastic shear flow stability with slip boundary conditions.
Main Results:
- Experimental evidence emphasizes the significance of the polymer-wall interface, particularly near the exit contact line.
- Wall slip and disentanglement of adsorbed polymers are crucial factors.
- Mathematical models show promise in predicting instability but require further refinement.
Conclusions:
- The sharkskin instability is strongly linked to polymer-wall interactions and slip dynamics.
- Further research is needed to differentiate between proposed mechanisms and refine predictive models.