Comparison between uniaxial and biaxial elongational flow behavior of viscoelastic fluids as predicted by differential constitutive equations

✍ Scribed by T. Isaki; M. Takahashi; T. Takigawa; T. Masuda

• Publisher: Springer-Verlag
• Year: 1991
• Tongue: English
• Weight: 617 KB
• Volume: 30
• Category: Article
• ISSN: 0035-4511
• DOI: 10.1007/bf00444371

✦ Synopsis

Behavior of polymer melts in biaxial as well as uniaxial elongational flow is studied based on the predictions of three constitutive models (Leonov, Giesekus, and Larson) with single relaxation mode. Transient elongational viscosities in both flows are calculated for three constitutive models, and steadystate elongational viscosities are obtained as functions of strain rates for the Giesekus and the Larson models.

Change of elongational flow behavior with adjustable parameter is investigated in each model. Steady-state viscosities ~/e and r/B are obtained for the Leonov model only when the strain-hardening parameter fl is smaller than the critical value tier determined in each flow. In this model, uniaxial elongational viscosity r/E increases with increasing strain rate e, while biaxial elongational viscosity ~/B decreases with increasing biaxial strain rate tB. The Giesekus model predictions depend on the anisotropy parameter a. r/E and y/~ increase with strain rates for small a, while they decrease for large a. When a is 0.5, r/e in increasing, but ~/B is decreasing. The Larson model predicts strain-softening behavior for both flows when the chain-contraction parameter ~' >0.5. On the other hand, when ~' is small, the steady-state viscosities of this model show distinct maximum around ~r = ~B T = 1.0 with relaxation time r. The maximum is more prominent in ~/e than in r/B.