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Lubricants 2018, 6(2), 52;

Low Friction, Lubricity, and Durability of Polymer Brush Coatings, Characterized Using the Relaxation Tribometer Technique

Laboratoire de Tribologie et Dynamique des Systèmes, UMR 5513, École Centrale de Lyon, Université de Lyon, 69134 Écully CEDEX, France
National Institute of Technology, Tsuruoka College, Tsuruoka 997-8511, Japan
This paper is an extended version of our paper published in WTC 2017.
Author to whom correspondence should be addressed.
Received: 16 March 2018 / Revised: 29 April 2018 / Accepted: 1 May 2018 / Published: 20 May 2018
(This article belongs to the Special Issue Selected Papers in the Sixth World Tribology Congress (WTC 2017))
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Among the possible solutions for achieving low friction, polymer brushes that are grafted onto surfaces are good candidates. The tribological characterization of such layers becomes more difficult when the friction is lower: the signal-to-noise ratio of the friction force that is measured with conventional tribometers impedes the precise quantification. Therefore, we have applied a new technique that has been developed at the Laboratory of Tribology and System Dynamics (LTDS), called the ‘oscillating relaxation tribometer’. The advantage of this original technique is that it characterizes low friction with unequalled sensitivity. The lower the friction, the better the precision, and it permits obtaining the ‘friction law’ directly from robust and rapid experimental tests. In this study, the samples that have been used are the ionic liquid-type polymer brushes (ILPBs) with different thicknesses, which have been grafted onto silicon wafers and steel coupons. The counter-face is a mirror-polished steel ball. We show that (i) a thick ILPB layer on silicon is very resistant to high contact pressure, up to 555 MPa; (ii) the friction behavior that is obtained is close to that of a Newtonian viscous one, even under maximum normal loads; (iii) poorer results are obtained for the thinner sample; and (iv) the repetition, up to 5000 oscillations on the same surface, does not affect the friction damping of the contact, which demonstrates that this film provides a favorable resistance to friction under severe contact conditions. In addition, the feasibility of grafting onto steel surfaces is demonstrated. The results are then discussed, with respect to friction and dissipation. View Full-Text
Keywords: ultra-low friction; polymer brushes; ionic liquids; relaxation tribometer; damping ultra-low friction; polymer brushes; ionic liquids; relaxation tribometer; damping

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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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Belin, M.; Arafune, H.; Kamijo, T.; Perret-Liaudet, J.; Morinaga, T.; Honma, S.; Sato, T. Low Friction, Lubricity, and Durability of Polymer Brush Coatings, Characterized Using the Relaxation Tribometer Technique . Lubricants 2018, 6, 52.

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