Research Papers: Lubricants

The Equation of State and the Temperature, Pressure, and Shear Dependence of Viscosity for a Highly Viscous Reference Liquid, Dipentaerythritol Hexaisononanoate

[+] Author and Article Information
Scott Bair

Georgia Institute of Technology,
Center for High-Pressure Rheology,
George W. Woodruff School of
Mechanical Engineering,
Atlanta, GA 30332-0405
e-mail: scott.bair@me.gatech.edu

Tsuyoshi Yamaguchi

Department of Molecular
Design and Engineering,
Graduate School of Engineering,
Nagoya University,
Furo-cho B2-3(611), Chikusa,
Nagoya, Aichi 464-8603, Japan
e-mail: tyama@nuce.nagoya-u.ac.jp

1Corresponding author.

Contributed by the Tribology Division of ASME for publication in the JOURNAL OF TRIBOLOGY. Manuscript received October 6, 2015; final manuscript received January 6, 2016; published online July 26, 2016. Assoc. Editor: Ning Ren.

J. Tribol 139(1), 011801 (Jul 26, 2016) (8 pages) Paper No: TRIB-15-1363; doi: 10.1115/1.4033050 History: Received October 06, 2015; Revised January 06, 2016

Measurements are reported for dipentaerythritol hexaisononanoate (DiPEiC9) of pressure–volume–temperature (pVT) response to pressures to 400 MPa and temperatures to 100 °C, and of viscosity at pressures to 700 MPa and temperatures to 90 °C and shear stress to 18 MPa. These data complement the low-shear viscosities published by Harris to pressures to 200 MPa and the compressions by Fandiño et al. to 70 MPa. The improved Yasutomi correlation reproduces all viscosity measurements with accuracy better than the Doolittle free volume and the Bair and Casalini thermodynamic scaling models which require an equation of state (EoS). The interaction parameter for thermodynamic scaling, γ = 3.6, is less than that reported by Harris (γ = 4.2) and the difference is primarily in the choice of EoS. The shear stress at the Newtonian limit, about 6 MPa, is exceptionally large given the high molecular weight of DiPEiC9. The large Newtonian limit is also seen in the oscillatory shear response.

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Fig. 1

Volume compressions of DiPEiC9 at three temperatures and compared to an 85 W-140 gear oil

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Fig. 2

Deviations of the Murnaghan EoS from the data of Fandiño et al. [16]. Volumes are relative to 100 °C.

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Fig. 3

The viscosities of this work as open points and the viscosities of Harris [15] as solid points. The curves are the improved Yasutomi model.

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Fig. 4

The viscosities of this work and Harris compared with the viscosity of three reference liquids and three commercial gear oils. The curves are the improved Yasutomi model with μg = 1012 Pa·s for all liquids.

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Fig. 5

The master curve for DiPEiC9 generated by plotting viscosity versus scaling parameter

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Fig. 6

Flow Curves for DiPEiC9 indicating an unusually high Newtonian limit stress

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Fig. 7

Flow curve generated with a cylinder set ordinarily used for polymer solutions. The solid curve is the Carreau Yasuda model with the same parameters as in Fig. 6. The dashed curve represents G = 2.5 MPa, the theoretical value.

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Fig. 8

The frequency dependent and steady shear dependent viscosity master curves for DiPEiC9. The relationship of steady shear dependence to oscillatory shear dependence is seen to be similar to that of SQL in Fig. 1 of Ref. [11] except that the Newtonian limit is greater.

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Fig. 9

Rendering of the molecular size, shape, and charge distribution of DiPEiC9 (at top) compared to SQL (SQL at bottom). (Courtesy of Arno Laesecke, NIST, Boulder, CO.) View “b” is view “a” rotated 90 deg counterclockwise viewed from the right-hand side. View “c” is view “a” rotated 90 deg counterclockwise viewed from the top.




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