Paraffin oil solutions of the mixture of sorbitan monolaurate–ethoxylated sorbitan monolaurate as lubricants

Paraffin mixtures of sorbitan monolaurate (SML)–ethoxylated sorbitan monolaurate (ESML) were applied as lubricant additives. The esters tested can be obtained from natural resources. They are environment-friendly. Tests under steady load conditions were performed to assess their tribological properties. The friction coefficient and wear scar diameter were measured. On the basis of the results obtained one can conclude that the mixtures tested significantly reduce motion resistance and wear. As compared to paraffin oil, wear scar diameter was reduced four times, while friction coefficient—even six times. The influence of total concentration and SML:ESML ratio on tribological properties was analyzed. The synergistic effect, attaining its optimum for comparable mole fraction of both esters, was observed. The results can be interpreted in terms of creation of micellar solutions and interaction of these structures with friction surface.