Rheology pp 63-68 | Cite as

Time Dependency of Extrudate Swell of Molten Polyethylene

  • J. M. Dealy
  • A. Garcia-Rejon


Extrudate swell is of interest to rheologists because it is one of the very few readily measured properties that provide information on the elastic response of a melt to shearing at high strain rates. For a capillary, which is the flow normally used for rheological characterization, there is only one swell ratio, B ≡ D/Do, and this is usually represented as a function of wall shear rate or wall shear stress for steady flow. In fact, the swell ratio is also time-dependent, so that the swelling of an element of extrudate depends on the time which has elapsed since that element left the die. This introduces an element of uncertainty into the meaning of reported values of swell measured in the laboratory, and White and Roman1 have pointed out that measured values depend strongly on the details of the technique used.


Shear Rate Wall Shear Stress High Density Polyethylene Annular Flow Wall Shear Rate 
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Copyright information

© Plenum Press, New York 1980

Authors and Affiliations

  • J. M. Dealy
    • 1
  • A. Garcia-Rejon
    • 1
    • 2
  1. 1.Department of Chemical EngineeringMcGill UniversityMontrealCanada
  2. 2.Facultad de QuimicaUniversidad Nacional Autonoma de MexicoMexico

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