Enhancement lubrication effect of a novel thiophosphate as additive of lithium complex grease in comparison to ZDDP

The demand of high-performance additives suitable for lubricating grease is increasing with the development of high-end equipment. Herein, a novel thiophosphate 3-(O, O- di-nonylphenol di-thiophosphate)-2-methylpropanoic acid (NDMA) was synthesized and added to lithium complex grease as an extreme pressure and anti-wear additive. The physicochemical, rheological, and tribological properties of NDMA were studied and compared with ZDDP. The results indicate that NDMA can improve and enhance oil separation under pressure and dropping point. NDMA showed better shearing resistance, friction reducing, anti-wear and load carrying capability than ZDDP. The lubrication mechanism of NDMA was demonstrated through molecular dynamics simulation. The results indicate that NDMA has strong adsorption capacity on sliding surfaces, promoting the tribo-chemistry reaction between NDMA and iron surfaces.