Abstract: Lanthanum dialkyldithiophosphate (LaDDP) was synthesized by using n-octanol, phosphorus pentasulfide and lanthanum nitrate as the primary raw materials. The structure of LaDDP was characterized by infrared spectroscopy(IR) and nuclear magnetic resonance spectroscopy (NMR). LaDDP was addedinto the base greaseprepared with 500N base oil and lithium stearate as thickener, and the performances of grease such as dropping point, penetration, oil separation (steel mesh method), extreme pressure, anti-wear properties and oxidation stability were tested. Moreover, the performance of LaDDP was compared with that of zinc dialkyldithiophosphate (ZDDP) when added to the same base grease.The results indicated that LaDDP significantly improved the oxidation stability of the base grease, and it is superior to ZDDP in terms of extreme pressure and colloid stability. These results demonstrated the potential of LaDDP as an effective additive for enhancing the performance of lubricating grease.The bond energy of the active site in the model compound LaDDP was calculated by molecular simulation, and the mechanism of extreme pressure and anti-wear properties of LaDDP in the friction process was speculated.

Key words: lanthanum dialkyldithiophosphate, lubricating grease, extreme pressure and wear resistance, molecular simulation