期刊
JOURNAL OF RHEOLOGY
卷 57, 期 1, 页码 293-313出版社
SOC RHEOLOGY
DOI: 10.1122/1.4767982
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资金
- EPSRC [GR/T11807/01, GR/T11821/01]
- European Union Marie Curie Initial Training Network DYNACOP [214627]
This work analyses the high-strain extensional behavior of long-chain branched polyethylenes, employing two novel extensional rheometer devices, the filament stretching rheometer and the cross-slot extensional rheometer. The filament stretching rheometer uses an active feedback loop to control the imposed strain rate on a filament, allowing Hencky strains of around 7 to be reached. The cross-slot extensional rheometer uses optical birefringence patterns to determine the steady-state extensional viscosity from planar stagnation point flow. The two methods probe different strain-rate regimes and in this paper we demonstrate the agreement when the operating regimes overlap and explore the steady-state extensional viscosity in the full strain-rate regime that these two complimentary techniques offer. For long-chain branched materials, the cross-slot birefringence images show a double cusp pattern around the outflow centre line (named W-cusps). Using constitutive modeling of the observed transient overshoot in extension seen in the filament stretching rheometer and using finite element simulations we show that the overshoot explains the W-cusps seen in the cross-slot extensional rheometer, further confirming the agreement between the two experimental techniques. (C) 2013 The Society of Rheology. [http://dx.doi.org/10.1122/1.4767982]
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