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

Abstract

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 analysisdifferential 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.