Abstract:The copper sheet was selected as metal material to be used in the high temperature thermal oxidation experiments of aviation lubricating oils by means of metal screening experiments.In the presence of metal and antioxidant,the hightemperature operating environment of aviation lubricating based oils including PAO and diisooctyladipate (DIOA) was simulated,and the variation of appearance,viscosity and acid value of the two oil samples after reaction were analyzed by contrast.The reason of oil property degradation was analyzed by FTIR.The results show that with the increasing of temperature,the color of PAO and DIOA oil samples is deepened,the kinematic viscosity is decreased and the acid value is increased due to the thermal oxidation and thermal cracking reactions of PAO and DIOA.According to the FTIR analysis results,it’s found that in the high temperature decay process,a large number of saturated hydrocarbons is produced for PAO oil samples,and the oxygen compounds,such as acid,aldehyde and ketone,are produced for the by the DIOA oil samples because of the hydrolysis of DIOA.The functional groups are found in the two kinds of oil samples,such as O=C-H,C=O,O-H and so on.The chain of PAO is easy to be broken under high temperature to produce the hydrocarbon molecules with less carbon number,leading to the sharply decreasing of viscosity at 260 ℃.While DIOA has good thermal stability,the sharply decreasing of viscosity is at about 300 ℃.The oxidation and cracking of the ester oil of DIOA will produce carboxylic acids,resulting in the acid value decay degree is much larger than that of PAO.
