Effect of particle size and ligand on the tribological properties of amino functionalized hairy silica nanoparticles as an additive to polyalphaolefin

Hairy nanoparticles, which graft organic chains on nanoparticles, have led to a wide variety of advanced materials and have been applied in many fields over the past two decades. In this paper, effects of nanoparticle size and organic chain on the tribological properties of amino functionalized hairy silica nanoparticles (HSNs) were investigated. Silica nanoparticles with different sizes and amino group organic chains were synthesized and dispersed into polyalphaolefin (PAO) via a modified process. The synthesized HSNs were characterized by variety of methods. The tribology properties of those HSNs were investigated using a four-ball tribometer. The coefficient of friction and wear scar diameter were measured and analyzed. It was found that the HSNs could form a stable homogeneous solution with PAO. The tribological performance of the PAO 100 was enhanced dramatically by adding the HSNs. The data suggested that HSNs with larger size, longer organic chains, and more amino groups gave better antiwear and friction reduction properties than other nanoparticles.