Lubrication, adsorption, and rheology of aqueous polysaccharide solutions

Stokes, Jason R., Macakova, Lubica, Chojnicka-Paszun, Agnieszka, de Kruif, Cornelis G. and de Jongh, Harmen H. J. (2011) Lubrication, adsorption, and rheology of aqueous polysaccharide solutions. Langmuir, 27 7: 3474-3484. doi:10.1021/la104040d

Author Stokes, Jason R.
Macakova, Lubica
Chojnicka-Paszun, Agnieszka
de Kruif, Cornelis G.
de Jongh, Harmen H. J.
Title Lubrication, adsorption, and rheology of aqueous polysaccharide solutions
Journal name Langmuir   Check publisher's open access policy
ISSN 0743-7463
Publication date 2011-04
Sub-type Article (original research)
DOI 10.1021/la104040d
Volume 27
Issue 7
Start page 3474
End page 3484
Total pages 11
Place of publication Washington, DC, United States
Publisher American Chemical Society
Collection year 2012
Language eng
Formatted abstract
Aqueous lubrication is currently at the forefront of tribological research due to the desire to learn and potentially mimic how nature lubricates biotribological contacts. We focus here on understanding the lubrication properties of naturally occurring polysaccharides in aqueous solution using a combination of tribology, adsorption, and rheology. The polysaccharides include pectin, xanthan gum, gellan, and locus bean gum that are all widely used in food and nonfood applications. They form rheologically complex fluids in aqueous solution that are both shear thinning and elastic, and their normal stress differences at high shear rates are found to be characteristic of semiflexible/rigid molecules. Lubrication is studied using a ball-on-disk tribometer with hydrophobic elastomer surfaces, mimicking biotribological contacts, and the friction coefficient is measured as a function of speed across the boundary, mixed, and hydrodynamic lubrication regimes. The hydrodynamic regime, where the friction coefficient increases with increasing lubricant entrainment speed, is found to depend on the viscosity of the polysaccharide solutions at shear rates of around 10 4 s -1. The boundary regime, which occurs at the lowest entrainment speeds, depends on the adsorption of polymer to the substrate. In this regime, the friction coefficient for a rough substrate (400 nm rms roughness) is dependent on the dry mass of polymer adsorbed to the surface (obtained from surface plasmon resonance), while for a smooth substrate (10 nm rms roughness) the friction coefficient is strongly dependent on the hydrated wet mass of adsorbed polymer (obtained from quartz crystal microbalance, QCM-D). The mixed regime is dependent on both the adsorbed film properties and lubricant's viscosity at high shear rates. In addition, the entrainment speed where the friction coefficient is a minimum, which corresponds to the transition between the hydrodynamic and mixed regime, correlates linearly with the ratio of the wet mass and viscosity at ∼10 4 s -1 for the smooth surface. These findings are independent of the different polysaccharides used in the study and their different viscoelastic flow properties
Keyword Quartz-Crystal Microbalance
Surface-Plasmon Resonance
Hydrophobic Surfaces
Steady Shear
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ
Additional Notes Received: October 7, 2010; Revised: February 1, 2011; Published: March 02, 2011

Document type: Journal Article
Sub-type: Article (original research)
Collections: School of Chemical Engineering Publications
Official 2012 Collection
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