High temperature is the main factor responsible for degrading the lubrication and antiwear properties of aero-lubricating oils. Accordingly, this study assessed the effects of thermal treatment of diester aviation lubricating oil and the associated mechanism. Fourier-transform infrared spectroscopy and gas chromatography/mass spectrometry analyses showed that low-molecular-weight compounds, such as monoesters, diesters, alcohols, and olefins, were the primary degradation products. An assessment of the degradation mechanism of bis(2-ethylhexyl)decanedioate showed that pyrolysis, resulting in the cleavage of β-C–H and C–C bonds, was the main process involved. Additional investigation using advanced polymer chromatography showed that the molecular weights of oil samples changed slightly at high temperatures, while the viscosity and viscosity-temperature index values were relatively stable. High-pressure differential scanning calorimetry established that the thermal oxidation stability of these oils decreased above 250°C. Finally, variations in the chemical compositions of the oil samples were found to be highly correlated with changes in physicochemical properties during thermal processing, with the formation of low-molecular-weight polar compounds greatly increasing the acid numbers of the oils.

中文翻译：

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温度对二酯航空润滑油化学成分和理化性能的影响

高温是导致空气润滑油的润滑和抗磨性能下降的主要因素。因此，本研究评估了二酯航空润滑油的热处理效果及其相关机理。傅里叶变换红外光谱和气相色谱/质谱分析表明，低分子量化合物（例如单酯，二酯，醇和烯烃）是主要的降解产物。对双（2-乙基己基）癸二酸酯的降解机理的评估表明，热解导致了β的裂解-C–H和C–C键是主要的过程。使用高级聚合物色谱的其他研究表明，高温下油样品的分子量略有变化，而粘度和粘度-温度指数值则相对稳定。高压差示扫描量热法确定了这些油的热氧化稳定性在250°C以上下降。最后，发现油样品的化学成分变化与热处理过程中的物理化学性质变化高度相关，低分子量极性化合物的形成极大地增加了油的酸值。