Structural analyses of viscosity index improvers in lubricant by means of small-angle X-ray scattering and dynamic light scattering

Takahashi, Ryohei*; Hirayama, Tomoko*; Tamura, Kazushi*; Sato, Nobuhiro*; Sugiyama, Masaaki*; Oba, Yojiro  

Viscosity index improvers (VII) are important additives for lubricants to suppress the temperature dependence of viscosity index. Although the temperature dependence of viscosity index of VII was thought to be related with the temperature dependence of nanostructures, only a few experimental results have been reported so far. Therefore, we performed small-angle X-ray scattering (SAXS) and dynamic light scattering (DLS) to characterize the nanostructures of VII in the lubricant. The results show the change in molecular size with increasing temperature. The relation between the viscosity index and the nanostructures are discussed.