Influence of Hydrocarbon Base Oil Molecular Structure on Lubricating Properties in Nano-scale Thin Film

In nano-scale thin film, the lubricant molecular structure may have more significant impact to lubricating performance than in bulk states. In order to investigate the influence of hydrocarbon base oil molecular structure to lubricating properties, three base oil samples with different molecular structure were synthesized in this study, the molecular structure was detected. Film thickness and friction coefficient were measured by EHD2 ultra thin film measurement system, and wear scar was evaluated by four-ball tester. The base oil with linear molecular structure show lower film thickness and friction coefficient, even the base oil has higher viscosity and viscosity index than other samples, while the branched structure makes the molecule more rigid than linear one, which increase the film thickness and friction coefficient. The linear molecules with high viscosity index sustained oil film at high temperature, which reduced the wear scar.