Tribological performance and mechanism of PMMA/SiO2 hybrid nanocomposite as lubricating oil additives

Polymethyl methacrylate/surface organically modified silica (PMMA/SiO2) hybrid nanocomposite was synthesized through 'one-step' soap-free emulsion polymerization. The resulting composite with core-shell structure was characterized by TEM. PMMA/SiO2 was well-dispersed spherical-shaped nano-particle with about 60 nm in diameter. The effect of PMMA/SiO2 hybrid nanocomposite as additives on the anti-wear and friction-reducing properties of AN 10 oil was examined using a four-ball friction and wear tester. PMMA/SiO2 hybrid nanocomposite was effective in improving steel-to-steel load-carrying capacity, anti-wear ability and in reducing friction coefficient of based oil, and it effectively enhanced extreme-pressure capacity of the based oil. Si element could not be detected on the worn steel surface under low load, when elastic roll of PMMA/SiO2 and formed films of polymer matrix on worn steel surfaces enhanced anti-wear and friction-reducing properties. A large amount of exposed high-active nano-SiO2 melted at middle and extreme loads and they deposited on the worn steel surface, and so they improved tribological performance of based oils.