The strain-hardening behaviour of linear and long-chain-branched polyolefin melts in extensional flows

Wagner, Manfred H.; Bastian, Heike; Hachmann, P.; Meißner, J.; Kurzbeck, Stefan; Münstedt, Helmut; Langouche, F.

doi:10.1007/s003970050010

Cited by 164 publications

(108 citation statements)

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“…The division by in Eq .2 , inherent to the DoiEdwards strain tensor, normalises the length of the deformed segments, but effectively draws the 'strain ellipse' back to being a 'strain sphere' (see Figure 1). Thus the Doi-Edwards model assumes a constant cross-section under elongation; the orientation of the segments is accounted for, but the stretching of the tube is not accounted for [19]. This indicates the need for 'f 2 u′ 2 ' in Eq.2.…”

Section: The Molecular Stress Function Modelmentioning

confidence: 99%

“…[18],and the Quadratic Strain Function (QMSF) for modelling long chain branched molecules; is derived in ref. [19] in parameter-free form:…”

Section: The Molecular Stress Function Modelmentioning

confidence: 99%

“…Significant improvement, particularly in capturing the rate of strain hardening, is suggested by use of the Molecular Stress Function (MSF) model [16][17][18][19][20]. The MSF model is based upon considerations of the geometry and stored energy of the polymer segments undergoing deformation; a particular version, the Quadratic Molecular Stress Function (QMSF) model [19] has been shown to fit transient planar elongation, uniaxial elongation, biaxial elongation and First and Second Normal Stress Difference measurements for strain hardening flows.…”

Section: Introductionmentioning

confidence: 99%

“…The MSF model is based upon considerations of the geometry and stored energy of the polymer segments undergoing deformation; a particular version, the Quadratic Molecular Stress Function (QMSF) model [19] has been shown to fit transient planar elongation, uniaxial elongation, biaxial elongation and First and Second Normal Stress Difference measurements for strain hardening flows. The accuracy of fit is remarkable particularly as only a single adjustable parameter is used in the model.…”

Section: Introductionmentioning

confidence: 99%

“…The single parameter QMSF model without constraint release, described in reference [19] has been shown to have many strong points. The model also has an elegant physical derivation in its favour, and provides a natural bridge between earlier KBKZ models, and the MSF with CCR model, described in ref.…”

Section: Introductionmentioning

confidence: 99%

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A study of the quadratic molecular stress function constitutive model in simulation

Olley

2005

Journal of Non-Newtonian Fluid Mechanics

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Constitutive models that conform to separable KBKZ specification have been shown to fit steady-state strain hardening rheological data in planar and uniaxial elongational flows, but with inaccuracy in the rate of strain hardening. The single parameter Molecular Stress Function model of Wagner [Rheol. Acta, 39 (2000), 97-109] has been shown to accurately fit the rise-rate in experimental data for a number of strain hardening and strain softening materials. We study this models accuracy against the well characterised IUPAC LDPE data, and present a method for full implementation of this model for flow solution which is suitable for incorporating into existing separable KBKZ software. A new method for particle tracking in arbitrarily aligned meshes, which is efficient and robust, is given. The Quadratic Molecular Stress Function (QMSF) model is compared to existing separable KBKZ based models, including one which is capable of giving planar strain hardening; the QMSF is shown to fit experimental rheological and contraction flow data more convincingly. The issue of 'negative correction pressures' notable in some Doi-Edwards based models is addressed. The cause is identified, and leads to a logical method of calculation which does not give these anomalous results.

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Section: The Molecular Stress Function Modelmentioning

confidence: 99%

“…[18],and the Quadratic Strain Function (QMSF) for modelling long chain branched molecules; is derived in ref. [19] in parameter-free form:…”

Section: The Molecular Stress Function Modelmentioning

confidence: 99%