The effect of temperature gradients on the sharkskin surface instability in polymer extrusion through a slit die

Miller, Erik, Lee, Sung J. and Rothstein, Jonathan P. (2006) The effect of temperature gradients on the sharkskin surface instability in polymer extrusion through a slit die. Rheologica acta, 45 6: 943-950. doi:10.1007/s00397-006-0086-2


Author Miller, Erik
Lee, Sung J.
Rothstein, Jonathan P.
Title The effect of temperature gradients on the sharkskin surface instability in polymer extrusion through a slit die
Journal name Rheologica acta   Check publisher's open access policy
ISSN 0035-4511
1435-1528
Publication date 2006-08-01
Sub-type Article (original research)
DOI 10.1007/s00397-006-0086-2
Open Access Status Not yet assessed
Volume 45
Issue 6
Start page 943
End page 950
Total pages 8
Place of publication Darmstadt, West Germany
Publisher Springer-Verlag
Language eng
Subject 090408 Rheology
Abstract The sharkskin surface instability is commonly observed in the extrusion of polymer melts. We present a series of experiments in which a specifically designed rectangular slit die with insulated and independently heated sides and is used to induce precise temperature gradients across a flowing polyethylene melt. Our previous experiments demonstrated that the character of the surface distortions produced by the sharkskin instability was a function of the die wall temperature and therefore the extrudate had viscoelastic properties at the surface. In this paper, we explore the role of temperature and viscoelastic property gradients near the capillary wall. The amplitude of the sharkskin instability is quantified and plotted against apparent shear and extension rates. Analysis of the data demonstrates that the amplitude and frequency of the instability is independent of bulk temperature and temperature gradient and is dependent only on wall temperature. The data are normalized using a dimensionless Weissenberg number based on the extension rate to collapse the data collected over all temperatures and gradients onto a single master curve. We conclude with an example of a rectangular extrudate exhibiting varying surface roughness due to differential die heating and discuss the implications of our observations on the sharkskin surface instability mechanism and on commercial applications
Keyword Polyethylene extrusion
Slit geometry
Sharkskin
Surface instability
Temperature gradients
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Unknown

Document type: Journal Article
Sub-type: Article (original research)
Collections: Excellence in Research Australia (ERA) - Collection
Australian Institute for Bioengineering and Nanotechnology Publications
 
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