| The aviation lubricating oil consisting of poly?-olefin?PAO?synthetic lubricating oil as based oil and mixed with other additives,appeared color deepening and viscosity thinning gradually with the development of high-performance.Moreover,the PAO aviation lubricating base oil?PALB?is completely dependent on imports at present.Once there are trade disputes or strategic resource blockade,China's national defense security will be seriously threatened.In this paper,I took domestic PAO aviation lubricating oil?DPALB?of independent intellectual property right as the experimental oil,comparing with the imported PAO aviation lubricating base oil?IPALB?,evaluated the differences of viscosity-temperature performance,low temperature fluidity,lubricity and other performance indicators comprehensively.Simulating the high-speed and high-shear working environment of aero-engine by using high-temperature reaction kettle,the differences of performance index between DPALB and IPALB under different working temperature,reaction time,reaction atmosphere,metal catalysis and antioxidant were investigated,and the decay ruler of color,viscosity,acid value and pour point of thermal oxidation test?TOT?oil samples were discussed.It was found that DPALB and IPALB both had good viscosity-temperature performance,low-temperature fluidity and low corrosiveness.Temperature was the main cause of PALB property decay.When the temperature was lower than 200 oC,the viscosity temperature relation of oxidation oil samples followed the Vogel equation.Compared with the oxidation stability of DPALB and IPALB according to the standard methods which were used in the pressure differential scanning calorimetry?PDSC?test and thermogravimetric analysis?TGA?.According to the test results of PDSC,TGA,and TOT,evaluated comprehensively the changes of the key performance indicators of the TOT oil samples,fitted the kinetic equation of TOT to calculate activation energy,and compared the perception of two lubricating oil on different types of antioxidants.The activation energy in TOT of DPALB and IPALB were 134.3 kJ·mol-1 and 99.94 kJ·mol-1,which indicated thermal stability of DPALB was superior to that of IPALB.Different antioxidants had different catalytic effects,while phenolic antioxidant T501 was suitable for low temperature oxidation reaction,and amine antioxidant Tz516 or T531 was more suitable for high temperature oxidation reaction.The antioxidant effect of the compound of T501 and Tz516 was better than any antioxidant used alone.The tribological properties of DPALB and IPALB and the anti-friction and anti-wear ability of DPALB test oil samples after TOT were investigated by four-ball machine test.Analyzed the load capacity of lubricating oil film qualitatively and quantitatively,evaluated the tribological properties of DPALB test oil samples adding the antioxidants.It was found that DPALB and IPALB had little difference in the extreme pressure?EP?behavior,anti-wear and anti-friction properties.Antioxidants can improve the tribological properties.The structures of DPALB and TOT oil samples under different reaction conditions were identified by FTIR analysis and GC/MS analysis.The effects of reaction temperature,atmosphere,metal Cu catalysis and antioxidant action on the test oil samples were qualitatively and quantitatively evaluated at molecular level.Meanwhile,enriched and extracted different polarity oxidation products of the 300°C TOT,with or without Cu and antioxidants using the methanol,acetone and ethyl acetate as extraction solvents,and the structure of key color-generating substances was identified at molecular level.IR and GC/MS analysis showed that DPALB was composed mainly of trimer of?-decene and a small amount of dimer and tetramer.When the reaction temperature was low,only less than 10%of the lubricating oil molecules cracked into small molecules of n-alkanes,isoparaffins and olefins,in contract when the temperature increased to 300°C,the relative content?RC?of cracked molecules reached nearly 30%.The chromophores with higher polarity were mainly concentrated in the methanol extract,which makes the color darker.Dienes,aldehydes,ketones and other complex structure of organic compounds increased the acid value and deepened oil color obviously.On the basis of GC/MS analysis of DPALB test samples and extracts,the mechanism of thermal cracking and thermal oxidation of PALB in the TOT was discussed thoroughly,and analyzed the effect of Cu and antioxidants on free radical reaction of lubricating oil.In the normal temperature,the structure and properties of the isoparaffin of PALB are stable,and is not easy to occur the chemical reaction,but when temperature incresded,the C-C bond at the tertiary carbon position in the saturated hydrocarbon molecule is inclined to breaking to form the primary carbon and secondary carbon free radicals,following the free radical reaction mechanism,and generates small molecular n-alkanes,isoparaffins and olefins through coupling reaction and disproportionation reaction.Oxygen promotes the generation of peroxy radicals and alkoxyl radical,while Cu reduces the Ea of free radical reaction.The number of free radicals increased,and the Ea decreased,which deepened the degree of free radical reaction,to generate more small molecular substances.Antioxidants T501 and Tz516 with the scissile O-H bond and N-H bond can capture free radicals preferentially,which reduced the number of free radicals in the system,and slowed down the free radical reaction process of lubricating oil. |
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