Abstract:Isothermal oxidation,pressurized differential scanning calorimetry and oxidation kinetics analysis were combined to study the oxidation performances of dipentaerythritol ester.The ester was oxidized at different temperatures respectively,and the effects of temperature and time on kinematic viscosities,viscosity indexes and acid values were analyzed.In order to compare the endurance of static oxidationat temperatures,the initial oxidation temperature,activation energy and oxidation rate constant of samples oxidized under various conditions were detected respectively.The results show that,the variation trends of kinematic viscosity and acid value are close to logistic function,that is,the kinematic viscosity and acid value increase slowly at the initial stage,then grow rapidly and reach the fastest rate,and finally the rate gradually decreases.High temperature oxidation above 180 ℃ leads to the significant changes of kinematic viscosity,viscosity indexes and acid values,while the variation trends are gentle at the temperature lower than 130 ℃,therefore,the dipentaerythritol ester can meet the operating requirement of refrigerator oil.High temperature oxidation above 180 ℃ results in the decrease of initial oxidation temperature,while it has less influence on the activation energy and oxidation rate constant.Hence,dipentaerythritol ester possesses good oxidation stability at high temperatures.