The tribological properties of the polyurea greases based on oil-miscible phosphonium-based ionic liquids

Oil-miscible phosphonium-based ionic liquids have recently been attracted much attention. This study is to develop potentional high temperature lubricating greases based on oil-miscible phosphonium-based ionic liquids. This lubricating grease is prepared using oil-IL blend, which was obtained by adding 10wt% oil-miscible phosphonium-based ionic liquids into the PAO 40 base oil as base stock. Compared with the traditional PAO 40 polyurea grease, this polyurea grease has a little lower dropping point. Corrosion test results show the polyurea grease that was prepared using phosphonium-based ionic liquids cations connected with longer alkyl chains that are no corrosion to brass and steel. Most importantly, the polyurea greases demonstrate very promising tribological properties at 150°C, such as low friction coefficient, small wear volume, and high lubrication failure load. Surface characterization revealed the tribochemical film containing iron oxide, and Fe[PO 4 ] was formed on the worn surface.