Synthesis of polyphenylmethylsiloxanes and their enhancement on tribological properties of titanium complex grease

Polyphenylmethylsiloxanes (PPMSs) with the phenyl/methyl mole ratios of 0.25:1–0.75:1 were facilely synthesized using phenylmethyldichlorosilane, diphenyldichlorosilane, dimethyldichlorosilane, and hexamethyldisiloxane as the raw materials with the hydrolysis-condensation method. The molecular weights (M _w) of the as-synthesized PPMSs ranged from 1248.7 to 27 014.0. The maximum molecular weight was obtained at the phenyl/methyl ratio of 0.65:1. Titanium complex greases were prepared by using titanium carboxylate as the thickener and PPMS/mineral oil (KN4010) as the mixed base oil. When the weight percentage of PPMS (phenyl/methyl mole ratio of 0.45:1) in the mixed base oil was 20%, the dropping point of the resultant titanium complex grease increased by 21 °C as compared with the sole mineral oil-based titanium complex grease. The friction coefficient and the wear scar dimension were 0.54 and 0.69 times those of the sole mineral oil-based titanium complex grease, respectively. According to thermogravimetric analysis–differential scanning calorimetry analysis, the working temperature of the titanium complex grease could reach 240 °C. The addition of PPMS in the titanium complex grease obviously improved its thermal stability and tribological properties. The present work developed a new category of titanium complex grease using PPMS and mineral oil as the mixed base oil. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47168.