Measurement and simulation of low-density polyethylene extrudate swell through a circular die

Journal Article

Background: Extrudate swell is a common phenomenon in polymer processing. The investigation of its mechanism is of both scientific and industrial interest. Results: The rheological parameters of a material described by the viscoelastic PTT (Phan-Thien-Tanner) constitutive model are obtained by fitting the distributions of material functions detected with a strain-controlled rheometer. The swelling ratios of low-density polyethylene (LDPE) under different volume flow rates are indirectly obtained using a photographic technique. A mathematical model of extrudate swell is established and its finite element model is derived. A penalty method is employed to solve the extrudate swell problem with a decoupled algorithm. Computation stability is improved by using the discrete elastic-viscous split stress algorithm incorporating the inconsistent streamline-upwind scheme. Conclusion: The swell phenomenon of LDPE through a circular die is investigated using both experimental measurement and numerical simulation. The swelling ratios obtained from the simulation are compared with those measured: they agree well with each other. The essential flow characteristics of polymer melts are predicted and the mechanism of the swell phenomenon is further discussed. © 2009 Society of Chemical Industry.

Full Text

Duke Authors

Cited Authors

  • Mu, Y; Zhao, G; Li, H; Liu, J; Xu, X; Mu, W; Chen, A

Published Date

  • 2009

Published In

Volume / Issue

  • 58 / 5

Start / End Page

  • 475 - 483

International Standard Serial Number (ISSN)

  • 0959-8103

Digital Object Identifier (DOI)

  • 10.1002/pi.2551