Abstract
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.
Highlights
High temperature is the main factor responsible for degrading the lubrication and antiwear properties of aero-lubricating oils
Ester oils prepared by dehydration and esterification reactions of acids and alcohols are relatively homogeneous [8], and ester lubricating oils (ELOs) show excellent resistance to thermal oxidation and wear, as well as low temperature fluidity, low volatility and toxicity, superior lubricating characteristics, and biodegradability [9,10,11]. erefore, these oils can play important roles, such as lubricating, cooling, antirusting, and sealing, under the harsh operating conditions found in aerospace applications and other industrial environments [12, 13]. e performance of ELOs is closely correlated with their molecular structure and chemical composition, while the viscosity and viscosity index of ELOs are largely determined by molecular conformation
Qian et al [27] examined the thermal oxidation mechanism of dioctyl adipate (DOA) using gas chromatography-mass spectrometry (GC-MS) and visual reactive force field molecular dynamics (ReaxFF MD). e results indicated that the acid number (AN) increased significantly and the tribological properties were improved owing to the formation of highly polar carboxylic acids and low-molecularweight monoesters
Summary
Each sample was subsequently cooled and filtered to obtain specimens referred to as DE180, DE200, DE230, DE250, DE270, and DE300, respectively. Prior to FTIR analysis, each sample was mixed with KBr and pressed into a pellet, from which spectra were recorded over the wavenumber range of 400–4000 cm−1. Degradation and oxidation of each of the seven oil samples were evaluated using the Synthetic Turbine Module from the InService Lubricants Analysis Pack in the FTIR software. E initial oxidation temperature (IOT) of each specimen was obtained based on the method QJ/DSH 275-1998. E specimen was heated from 50 to 300°C at 20°C min−1 under an oxygen flow rate of 20 mL min−1 and oxygen pressure of 3.5 MPa. e oxidation induction time (OIT) was determined using the method SH/T 0719-2002. High-purity oxygen was rapidly passed into the heating chamber until the oxygen pressure reached 3.5 MPa, after which oxygen flow was kept constant at 20 mL min−1
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
