Thermophysical and tribological properties of dispersions based on graphene and a trimethylolpropane trioleate oil

The objective of this work is to study the tribological and thermophysical properties of nanolubricants composed by a trimethylolpropane trioleate (TMPTO) oil, and graphene nanoplatelets (GnP). For this aim, nanolubricants based on TMPTO with 0.05, 0.10, 0.25 and 0.50 wt% of graphene nanoplatelets were prepared. The dependence on temperature and concentration of the viscosity, density and speed of sound was determined by means of a rotational viscometer and two mechanical oscillation densimeters. Likewise, the antifriction and antiwear properties of these nanolubricants were analyzed. For this purpose, tribological tests were carried out at room temperature in a tribometer operating in ball on plate configuration and in reciprocating mode under a working load of 2.5 N. A 3D optical profilometer was used to analyze the wear track through the width of the scar. As regards thermophysical behavior of density and viscosity, both increase as the concentration of nanoparticles increases, whereas the speed of sound slightly diminishes when the GnP concentration increases. The best antifriction-antiwear performance was obtained for the nanolubricant containing 0.25 wt% in GnP.