The effect of molecular structure of lubricant polyol ester base oils on friction was studied. A Mini-Traction Machine was used to produce Stribeck curves under representative oil system conditions. The base oils were examined independent of viscosity to isolate the impact of the molecular structure. The effect of chain length, the number of ester groups and the effect of branching were investigated. Friction decreases as the chain length increases, as the number of ester groups increases and as the amount of branching decreases. The decrease in friction as the chain length and number of ester groups increases was attributed to improved packing efficiency and that longer chains can better separate surfaces. However, branching increases friction due to hindering packing efficiency.
- Base oil