Evalution of Thermal Oxidative Degradation of Trimethylolpropane Trioleate by TG/DTA/DSC

Abstract

In order to evaluate the thermal oxidation degradation behavior of lubricant with different antioxidants, the thermal kinetics equation based on the anlyses of thermogravimetry(TG), differential thermal analysis(DTA), and differential scanning calorimetry(DSC) was established, respectively, to calculate the activation energy of lubricant thermal-oxidative reaction. The thermal analyses of TG and DTA were employed to determine the thermal decomposition properties of ester oils trimethylolpropane trioleate(TMPTO) with butyloctyl-diphenylamine/octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanoate/amine-phenol combination antioxidant. The activation energy of the lubricating oil adding antioxidant is increased relative to the TMPTO base oil, and the order of activation energy are E _c (93.732 kJ·mol⁻¹)>E _d (88.71 kJ·mol⁻¹)>E _b (58.41 kJ·mol⁻¹) >E _a (46.32 kJ·mol⁻¹). The experimental results show that octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propanoate in TMPTO has favorable resistance to thermal oxidation and decomposition. The thermal analysis method of DSC accurately reflects the heat exchange of lubricant thermal-oxidative reaction. The order of activation energy is calculated to E _D (144.385 kJ·mol⁻¹) > E _C (110.05 kJ·mol⁻¹) > E _B (97.187 kJ·mol⁻¹) > E _A (66.02 kJ·mol⁻¹). It is illustrated that the amine-phenol combination antioxidant has the best thermal oxidation resistance, which is the same as what the oxidation onset temperature effected.

Keywords

thermal oxidative degradation / thermal kinetics / antioxidants / trimethylolpropane oleate