Significance Statement
The interdisciplinary approach discussed herein shows the potential of novel polymeric lubricants involving ionic liquids (ILs). In general, siloxanes are known as cost-efficient high performance lubricants but with rather poor tribological capabilities. On the other hand, the investigation of ILs as lubricants has demonstrated that these novel substances are able to provide remarkable protection against wear and significantly reduce friction whether they are proposed as additives or in the neat form. Consequently, linking ionic groups to polysiloxane-polyalkylene oxide copolymers is expected to yield a lubricating material that combines the favorable properties of the constituents. We focused on fundamental investigations of IL-modified copolymers behaviour in comparison to their respective precursor copolymers. Furthermore, issues related to synthesis, viscometrical data, thermal-oxidative stability, tribology in steel-polymer and steel-steel contacts, as well as corrosiveness have been discussed in-depth. Moreover, the importance of structure confirmation of the synthesized IL-modified copolymers was demonstrated.
The findings obtained in this work suggest a fundamental, yet systematic approach of ionic liquids incorporated in siloxane copolymer lubricants for friction and wear reduction, and open up new opportunities for further research steps in terms of molecular design, synthesis and structure-property relationships.
Journal Reference
Tribology International, Volume 67, 2013, Pages 1–10.
Vladimir Totolina, Natalia Ranetcaiab, Viorica Hamciucb, Nicholas Shorea, Nicole Dörra, Constanta Ibanescuc, Bogdan C. Simionescub,c, Valeria Harabagiub
a AC²T Research GmbH, Wiener Neustadt, Austria and
b Petru Poni Institute of Macromolecular Chemistry, Iasi, Romania and
c Gheorge Asachi Technical University of Iasi, Romania.
Abstract
Lubricants based on ionic liquid (IL) modified poly(dimethylsiloxane–alkylene oxide) graft co-polymers (GC) were synthesised by condensation of hydroxyalkyl groups linked to GC chains and to IL moieties. The tribological performances of neat and IL-modified co-polymers were investigated in reciprocating steel–steel and in rotating steel–PTFE contacts at 30 and 100 °C. A clear dependence of friction and wear on temperature was observed for both neat and IL-modified co-polymers. Generally, friction decreased at higher temperature, especially pronounced for neat co-polymers. Neat as well as IL-modified co-polymers tend to increase wear at elevated temperature. At 30 °C, the IL-modified co-polymers exhibited significantly improved anti-wear properties when compared to neat co-polymers with bis(trifluoromethylsulfonyl)amide anion being the crucial moiety involved in tribochemical reactions.