Two phosphonium cation-based ionic liquids used as lubricant additive

The lubricant film thickness and friction properties of a mineral base oil and its mixtures with two phosphonium cation-based ionic liquids: [P66614][(iC8)2PO2] and [P66614][BEHP] at 0.5 and 1 wt% concentrations were studied under different slide-to-roll ratios (SRR) and temperatures in an EHD2 ball-on-disc test rig. All lubricant samples showed similar lubricant film thickness in full film lubrication and behaved similarly in friction tests with polished discs at SRR of 5%, but the mixtures outperformed the neat base oil at SRR of 50%. The mixtures were also better in tests with rough discs. Tribological improvements with mixtures were achieved under mixed and boundary lubrication regimes. Real application such as rolling bearings will be presented in the second part of this work.