Abstract
In recent years, environmental pollution and depletion of energy resources have been discussed as problems, and technologies for higher efficiency are required. Lubricants are used in gasoline vehicle transmissions to reduce friction, and ester mixed lubricants are used in boundary lubrication conditions where solid contact is severe. Ester mixted lubricants increase oil film thickness by adhering to metal surfaces to reduce friction, but it has been found that esters containing unsaturated fatty acids undergo thermal denaturation during friction. In this study, the effects of thermal denaturation of esters on friction properties were elucidated. Friction tests were conducted at 23°C, 60°C, and 80°C using lubricants with unsaturated fatty acids (TMPTO) added to the base oil (PAO), and the friction coefficient was the largest at 60°C and the smallest at 80°C. The oil film thickness was the smallest at 60°C and the friction coefficient was the largest at 80°C. The coefficient of determination between the friction coefficient and oil film thickness is 0.73, which means that the assumed oil film model is correct. This suggests that the effect of surface adsorption is stronger at low temperatures, while the effect of thermal denaturation of TMPTO with high viscosity is stronger at high temperatures, suggesting that more thermal modification products may be produced at high temperatures.
