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Effect of Accelerated Aging on the Chemical Signature and Performance of a Multiply-Alkylated Cyclopentane (MAC) Lubricant for Space Applications
Tribology Letters ( IF 2.9 ) Pub Date : 2020-12-08 , DOI: 10.1007/s11249-020-01372-z
Archim Wolfberger , Martin Zehl , Andreas Hausberger , Martin Tockner , Sandra Schlögl , Małgorzata Hołyńska , Christopher Semprimoschnig

The thermo-oxidative degradation of a multiply-alkylated cyclopentane (MAC) lubricant for space applications is investigated. Accelerated aging tests at temperature levels between 60 °C and 150 °C are performed and the aging behavior is investigated in detail with spectroscopic, mass spectrometric and chromatographic techniques as well as tribological testing on a ball-on-disk setup. The degree of oxidative aging of the MAC lubricant is monitored with the carbonyl index (CI), which is shown to be well-suited to monitor the degree of degradation of the lubricant. Gas chromatography/mass spectrometry (GC/MS) analysis is applied to identify 9-nonadecanone as the main volatile degradation product in all aged samples, suggesting a similar decomposition pathway at all tested temperatures. Size exclusion chromatography (SEC) is further applied to confirm the formation of higher molecular weight degradation products upon aging, affecting the viscosity of the lubricant. In the subsequent ball-on-disk tests, a good correlation of the performance loss with the FTIR measurements is seen and CI values of approx. 0.64 are regarded as threshold for the complete loss of performance at the selected test conditions. The determined CI values in dependence of the aging duration are further used to perform a time–temperature superposition (TTS) to acquire a master curve for accelerated aging. In the resulting Arrhenius plot, non-linear behavior is observed, highlighting the importance of a precise control of accelerated aging parameters for reliable lifetime estimations.



中文翻译:

加速老化对用于太空应用的多烷基化环戊烷(MAC)润滑剂的化学特征和性能的影响

研究了用于太空应用的多烷基化环戊烷(MAC)润滑剂的热氧化降解。在60°C和150°C之间的温度水平下进行了加速老化测试,并通过光谱,质谱和色谱技术以及在圆盘上进行的摩擦学测试详细研究了老化行为。MAC润滑剂的氧化老化程度可以通过羰基指数(CI)进行监测,该羰基指数非常适合于监测润滑剂的降解程度。气相色谱/质谱(GC / MS)分析用于确定9-十八烷酮为所有老化样品中的主要挥发性降解产物,表明在所有测试温度下均具有相似的分解途径。尺寸排阻色谱法(SEC)进一步用于确认老化后会形成较高分子量的降解产物,从而影响润滑剂的粘度。在随后的圆盘球测试中,可以看到性能损失与FTIR测量值之间具有良好的相关性,CI值大约为1。0.64被视为在所选测试条件下性能完全丧失的阈值。根据老化时间确定的CI值还可用于执行时间-温度叠加(TTS),以获取加速老化的主曲线。在所得的Arrhenius图中,观察到非线性行为,突出显示了精确控制加速老化参数对于可靠的寿命估算的重要性。影响润滑剂的粘度。在随后的圆盘球测试中,可以看到性能损失与FTIR测量值之间具有良好的相关性,CI值大约为1。0.64被视为在所选测试条件下性能完全丧失的阈值。根据老化时间确定的CI值还可用于执行时间-温度叠加(TTS),以获取加速老化的主曲线。在所得的Arrhenius图中,观察到非线性行为,突出显示了精确控制加速老化参数对于可靠的寿命估算的重要性。影响润滑剂的粘度。在随后的圆盘球测试中,可以看到性能损失与FTIR测量值之间具有良好的相关性,CI值大约为1。0.64被视为在所选测试条件下性能完全丧失的阈值。根据老化时间确定的CI值还可用于执行时间-温度叠加(TTS),以获取加速老化的主曲线。在所得的Arrhenius图中,观察到非线性行为,突出显示了精确控制加速老化参数对于可靠的寿命估算的重要性。64被认为是在所选测试条件下性能完全丧失的阈值。根据老化时间确定的CI值还可用于执行时间-温度叠加(TTS),以获取加速老化的主曲线。在所得的Arrhenius图中,观察到非线性行为,突显了精确控制加速老化参数对于可靠的寿命估算的重要性。64被认为是在所选测试条件下性能完全丧失的阈值。根据老化时间确定的CI值还可用于执行时间-温度叠加(TTS),以获取加速老化的主曲线。在所得的Arrhenius图中,观察到非线性行为,突出显示了精确控制加速老化参数对于可靠的寿命估算的重要性。

更新日期:2020-12-08
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