Chemically functionalized graphene oxide with N-phenyl-p-phenylenediamine as efficient tribo- and rheological modifier for lubricating oil

Nanoadditive with multifunctional properties holds commercial importance in the lubricant industry. Herein, GO-N-PPDA was synthesised as nanoadditive by functionalizing graphene oxide (GO) using N-phenyl-p-phenylenediamine and characterised by Fourier transform infrared spectroscopy, X-ray diffraction analysis, thermogravimetric analysis, scanning electron microscopy and transmission electron microscopy analysis. The antioxidant behaviour of GO-N-PPDA was analysed by 2,2-diphenyl-1-picryl-hydrazyl-hydrate. The nanoparticles dispersed mineral base oil (N-250) in 0.2%, 0.4%, 0.6% (w/v) concentrations were evaluated for tribological, rheological and thermophysical analysis by ASTM methods. The flow behaviour of the nanolubricant shows shear thickening behaviour with an increase in shear rate. In contrast, tribological results indicate a significant reduction in wear scar diameter and coefficient of friction to the base oil. Furthermore, GO-N-PPDA shows improved thermophysical properties compared with the mineral base oil. Thus, GO-N-PPDA shows multifunctional behaviour in terms of viscosity index, pour point, antioxidant activity, rheology and tribological properties.