Chemically modified graphene oxide with fatty alcohol as antiwear, antifriction and rheology modifier for lubricating oil

Graphene oxide is a diverse material for surface modification due to many –OH and –COOH groups present at terminal positions. This study reported the synthesis of nanoadditive from graphene oxide (GO) and hexadecanol (HD). The nanoadditive synthesized form was characterized by routine spectroscopic techniques like Fourier transform-infrared, X-ray diffraction and scanning electron microscopy. The thermal stability of a nanoadditive was further examined using thermogravimetric analysis. After confirming GO-HD formation, it was dispersed in mineral base oil (N-250) in three different compositions (0.2, 0.4 and 0.6% w/v) by ultrasonication method. The nanoadditives doped mineral oil was evaluated using standard ASTM methods for physicochemical analysis like kinematic viscosity, viscosity index and pour point. It was observed that GO-HD shows a considerable improvement in viscosity index and pour point at lower concentrations. Further, the resulting lubricant-doped GO-HD was also analysed for rheological and tribological analysis using Anton Paar MCR-72 and ASTM D4172 methods. It was observed that nanoadditives-doped lubricant exhibits non-Newtonian behaviour with respect to the base oil, whereas tribological results indicate a significant reduction in wear scar diameter ~9.5% and coefficient of friction ~11.8% as compared to the mineral base oil. Therefore, GO-HD nanoadditive shows multifunctional behaviour in terms of viscosity index, pour point, rheology and enhancement in antiwear and antifriction properties. The stable dispersion of chemically functionalized GO-HD provides low resistance sheared between the contacting surfaces due to the weak van der Waals interaction between their lamellas, thus significantly reducing both the friction and the wear. Graphical abstract