Effect of the concentration of carbon nanotubes (CNTs) on the rheological behavior in a lubricating oil of plant-derived lubricant

Nanofluids have attracted a lot of attention since their significant enhancement in thermal properties, however there are few reports on the study of the viscosity of nanofluids from an experimental point of view. In this work, the rheological behavior of functionalized multi-walled carbon nanotubes (F-MWCNTs) and coated with MoS₂ (MWCNTs-MoS₂) in a commercial palm oil as base fluid was evaluated. The purification and functionalization process of the MWCNTs was performed by acid leaching and investigated by FTIR, and stable nanofluids were prepared with MWCNTs concerning time. The rheological behavior of nanofluids with MWCNTs was performed as a function of temperature at different concentrations (0.1, 0.5 and 1% wt.). The effect of time, temperature, shear rate and shear stress versus shear rate were determined. The results indicate that the nanofluid behaves as a Newtonian fluid independently of the MWCNTs concentrations and temperatures evaluated. The viscosity index increases by 16% at a concentration of 1% wt. of F-MWCNTs and for nanofluids added with MWCNTs-MoS₂ had significant effect on the effect of temperature.