Abstract:The application of nano-TiO2 in the lubricating oil industry was seriously restricted because of its low dispersion stability. In this paper, tetrabutyl titanate (TBT) was used as the initiator to initiate the ring opening polymerization of δ-Valerolactone (DVL) at 60 ℃ to produce four arm star shaped polyvalerolactone (4-PVL), and then the oil soluble nano-TiO2 was hydrolyzed under acid condition. The Scanning electron microscopy (SEM) showed that the product nano-TiO2 had spherical particles of uniform size, with an average diameter of about 20-30 nm. This modification process was feasible, which was demonstrated by Fourier Transform Infrared Spectrometry (FT-IR), termogravimetric analysis (TG) and X-raw Diffraction (XRD). It had been proved that the dispersion stability of nano-TiO2 in base lubricating oil had been significantly optimized which could keep the stability of dispersion for 2 months without obvious precipitation. Lubricant with nano-TiO2 additive showed lower friction coefficient and wear spot diameter due to the “bearing effect” and “filling and repairing effect”. The friction coefficient of composite nano-base oil varied from 0.049 to 0.025, and the average wear spot diameter decreased from 1028 μm to 979 μm. Compounded nano-TiO2 lubricant exhibited excellent anti-wear and self-repairing performance.