Rheological and tribological properties of polyurea greases containing additives of MoDDP and PB

Molybdenum dialkyl dithiophosphate (MoDDP) and potassium borate (PB) were selected as additives for the greases. Results show that the polar MoDDP additive cause grease colloidal stability enhanced and apparent viscosity and structural strength increased, while potassium borate has less effect on the colloidal structure and structural strength of the grease. The solid additive PB has excellent anti-wear, extreme pressure and friction reduction properties at room temperature as well as at high temperatures under low loading conditions. Due to the synergistic effect, the PB/MoDDP additive combination can achieve excellent friction reduction and anti-wear performance. Under high temperatures, the content of metal phosphates and molybdenum disulfide decreases, the adsorption capacity of additives decreases, and friction and wear on metal surfaces increase.