Lubrication of starch in ionic liquid-water mixtures: soluble carbohydrate polymers form a boundary film on hydrophobic surfaces
Date
2015
Authors
Yakubov, G.E.
Zhong, L.
Li, M.
Boehm, M.W.
Xie, F.
Beattie, D.A.
Halley, P.J.
Stokes, J.R.
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Journal article
Citation
Carbohydrate Polymers, 2015; 133:507-516
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Abstract
Soluble starch polymers are shown to enhance the lubrication of ionic liquid-water solvent mixtures in low-pressure tribological contacts between hydrophobic substrates. A fraction of starch polymers become highly soluble in 1-ethyl-3-methylimidazolium acetate (EMIMAc)-water solvents with ionic liquid fraction ≥60 wt%. In 65 wt% EMIMAc, a small amount of soluble starch (0.33 wt%) reduces the boundary friction coefficient by up to a third in comparison to that of the solvent. This low-friction is associated with a nanometre thick film (ca. 2 nm) formed from the amylose fraction of the starch. In addition, under conditions where there is a mixture of insoluble starch particles and solubilised starch polymers, it is found that the presence of dissolved amylose enhances the lubrication of starch suspensions between roughened substrates. These findings open up the possibility of utilising starch biopolymers, as well as other hydrocolloids, for enhancing the performance of ionic liquid lubricants.
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Data source: Supplementary data, http://www.sciencedirect.com/science/article/pii/S0144861715006050
Link to a related website: http://wrap.warwick.ac.uk/114464/1/WRAP-lubrication-starch-ionic-liquid-water-mixtures-soluble-hydrophobic-Xie-2015.pdf, Open Access via Unpaywall
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Copyright 2015 Elsevier