Effect of Temperature on the Composition of a Synthetic Hydrocarbon Aviation Lubricating Oil

Abstract

Synthetic hydrocarbon aviation lubricating oils (SHALOs) gradually degrade over time when subjected to high temperatures, resulting in their composition and properties varying over the operation lifetime. Therefore, understanding the SHALO degradation properties by elucidating the mechanism on a molecular level, as a function of high temperature, is of interest. A SHALO was subjected to thermal treatment (TT) at 180, 200, 230, 250, 270, or 300 °C for 2 h. The chemical compositions of six TT samples and one fresh oil were analyzed by fourier transform infrared F spectroscopy, advanced polymer chromatography, and gas chromatography/mass spectrometry. Furthermore, the physicochemical properties, such as kinematic viscosity, pour point, and acid number, of seven samples were determined. The oil samples were grouped by cluster analysis (CA) using a statistical method. The SHALO was identified to comprise 20 functional groups, including comb-like alkanes, long-chain diesters, amines, phenols, and other compounds. TT at <230 °C caused partial cracking of the SHALO base oils, with a concomitant change in the antioxidant content and type, and the polycondensation reactions were dominant. The observed antioxidant changes were not obvious from TT at >230 °C. A large number of small-molecule compounds were detected, including n-alkanes and olefins. TT at 250 °C was shown to be an important threshold for the kinematic viscosity, pour point, and acid number of the samples. Below 250 °C, the sample properties were relatively stable; but at elevated TT temperatures (>250 °C), the properties were observed to dramatically degrade. As the sample color was highly sensitive to temperature, the TT temperature induced rapid and significant color changes. The CA analysis results for the oil compounds at the molecular level were in good agreement with observed changes in the physicochemical properties at the macro level.

Recent Advances in Separation-Based Techniques for Synthetic Polymer Characterization

“…In more recent publications, APC technology has been demonstrated as an efficient tool for rapid and highly informative characterization of synthetic hydrocarbon aviation lubricating oils (SHALOs), polystyrenes bearing aldehyde chain end functionality, technical lignins, depolymerization products of lignosulfonates and starches …”

“…In more recent publications, APC technology has been demonstrated as an efficient tool for rapid and highly informative characterization of synthetic hydrocarbon aviation lubricating oils (SHALOs), 21 polystyrenes bearing aldehyde chain end functionality, 22 technical lignins, 23 depolymerization products of lignosulfonates 24 and starches. 25 An APC technique for rapid determination of molecular weight and distribution of acid catalyzed depolymerization products of lignosulfonate at different temperatures (70, 100, and 130 °C) was reported.…”

Effect of Temperature on the Chemical Composition and Physicochemical Properties of Diester Aviation Lubrication Oil

“…Minimal changes occurred in the RCs of these compounds with heating. As summarized in Table 1, dioctyldiphenylamine (50) in the oils generated N-(2-methylheptan-2-yl)-N-phenylaniline (25) and bis(4-(tert-butyl)phenyl)amine (26), while triphenyl phosphate (28), diphenyl tolyl phosphate (29,31,32), and phenyl ditolyl phosphate (36,38,40) were produced from tri-otolyl phosphate. It was reasonably inferred that the antioxidants and antiwear agents were all unstable, even under storage conditions.…”

“…Prior to analysis, samples (5 mg) were dissolved in THF (1.5 mL) and the injection volume was set at 10 μL. ese analysis conditions were based on a previously reported procedure [31].…”

Sliding bearings with lead-bismuth liquid metal lubrication

“…The use of oils for lubricating bearings at high temperatures is limited by the temperature regime of their operation and, as a rule, it is about 250 °C [1]. With an increase in temperature in the friction unit, special design improvements or an increase in the operating temperature of the lubricant are required.…”