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Research Papers: Elastohydrodynamic Lubrication

Correlation of Polysiloxane Molecular Structure to Shear-Thinning Power-Law Exponent Using Elastohydrodynamic Film Thickness Measurements

[+] Author and Article Information
Thomas J. Zolper

Department of Mechanical Engineering,
University of Wisconsin,
Platteville, WI 53818
e-mail: Zolpert@uwplatt.edu

Paul Shiller, Gary Doll

Department of Civil Engineering,
University of Akron,
Akron, OH 44325

Manfred Jungk

Dow Corning GmbH,
Rheingaustr. 34,
Weisbaden 65201, Germany

Tobin J. Marks

Department of Chemistry,
Northwestern University,
Evanston, IL 60208

Yip-Wah Chung

Department of Materials
Science and Engineering;
Department of Mechanical Engineering,
Northwestern University,
Evanston, IL 60208

Aaron Greco

Energy Systems Division,
Argonne National Laboratory,
Argonne, IL 60439

Babak LotfizadehDehkordi

Department of Mechanical Engineering,
University of Akron,
Akron, OH 44325

Qian Wang

Department of Mechanical Engineering,
Northwestern University,
Evanston, IL 60208

1Corresponding author.

Contributed by the Tribology Division of ASME for publication in the JOURNAL OF TRIBOLOGY. Manuscript received July 30, 2014; final manuscript received February 18, 2015; published online April 15, 2015. Assoc. Editor: Zhong Min Jin.

The United States Government retains, and by accepting the article for publication, the publisher acknowledges that the United States Government retains, a non-exclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this work, or allow others to do so, for United States Government purposes.

J. Tribol 137(3), 031503 (Jul 01, 2015) (10 pages) Paper No: TRIB-14-1192; doi: 10.1115/1.4029940 History: Received July 30, 2014; Revised February 18, 2015; Online April 15, 2015

Siloxane-based polymers (polysiloxanes) are susceptible to temporary shear-thinning that manifests as a reduction of elastohydrodynamic film thickness with increasing entrainment speed or effective shear rate. The departure from Newtonian film thickness can be predicted with the power-law exponent ns, an indicator of the severity of shear-thinning in a polymeric fluid that is influenced by the macromolecular structure. In this paper, a combination of extant rheological and tribological models is applied to determine the power-law exponent of several polysiloxanes using film thickness measurements. Film thickness data at several temperatures and slide-to-roll ratios are used to validate the methodology for several siloxane-based polymers with alkyl and aryl branches.

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References

Figures

Grahic Jump Location
Fig. 1

General molecular structure of siloxanes depicting branch content (Q), pendant group (J), alkyl length (L), and degree of polymerization (DP) from Zolper et al. [5,15]

Grahic Jump Location
Fig. 2

Measured (symbols) and calculated (lines) film thickness versus entrainment speed for siloxane lubricants (a) D-F, (b) A100-12, and (c) P90 at 303 K (triangles), 348 K (squares), and 398 K (diamonds)

Grahic Jump Location
Fig. 3

Calculated (lines) coefficient of determination (R2) versus power-law exponent for siloxane lubricants (a) D-F, (b) A100-12, and (c) P90 at 303 K, 348 K, and 398 K

Grahic Jump Location
Fig. 4

Measured (symbols) and calculated (lines) film thickness versus entrainment speed for siloxane lubricant P10-B at (a) 303 K and (b) 398 K and slide-to-roll of Σ = 0 (triangles), Σ = 0.5 (squares), and Σ = 1 (diamonds)

Grahic Jump Location
Fig. 5

Calculated (lines) coefficient of determination (R2) versus power-law exponent for siloxane lubricant P10-B at (a) 303 K and (b) 398 K and slide-to-roll of Σ = 0 (black dot), Σ = 0.5 (gray dash), and Σ = 1 (black dash)

Grahic Jump Location
Fig. 6

Calculated (symbols) power-law exponent versus shear modulus for siloxane lubricants including PDMS (squares), PPMS (diamonds), and PAMS (triangles)

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