Citric Acid-Based Esters as Potential Synthetic Lubricants: A Study of Their Synthesis, Rheological Properties and Thermal Stability

The failure of mineral oils to work in machinery and engines under intense pressure, heat, and corrosion has prompted researchers to consider the development of synthetic lubricating oils that are appropriate for these demanding conditions. This research was conducted to synthesize new esters by rea...

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Bibliographic Details
Published in:Tribology transactions 2023-11, Vol.66 (6), p.1095-1104
Main Authors: Haseeb, Mohamed E., Nasser, Rabab M., Nassar, Amal M., Ahmed, Nehal S.
Format: Article
Language:English
Subjects:
Acids
Citric acid
Decanol
Esters
Fourier transforms
Infrared analysis
Infrared spectroscopy
Low temperature
Lubricants
Lubricating oils
Mineral oils
NMR
NMR spectroscopy
Nuclear magnetic resonance
Octanoic acid
Octanol
Propane
Propionic acid
Rheological properties
Rheology
Shear rate
Spectrum analysis
Thermal analysis
Thermal stability
Thermogravimetric analysis
Valeric acid
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Summary:The failure of mineral oils to work in machinery and engines under intense pressure, heat, and corrosion has prompted researchers to consider the development of synthetic lubricating oils that are appropriate for these demanding conditions. This research was conducted to synthesize new esters by reaction of citric acids (CA) with mono-alcohols (hexanol, octanol, decanol and 2-ethylhexanol), then the products were reacted with propanoic acid, valeric acid, and octanoic acid separately using 1:1 molar ratio. The resulting esters were characterized using nuclear magnetic resonance spectroscopy (NMR), Fourier-transform infrared spectroscopy (FTIR), and thermal gravimetric analysis (TGA). The rheological properties were studied, and it was found that the prepared esters have high thermal stabilities as the degradation takes place in the range of 175 °C - 425 °C. The prepared esters show Newtonian behaviors as their viscosities do not change by changing shear rate. The physicochemical characteristic of prepared esters were also determined which showed improved low temperature properties (PP) -36 °C for ester (2R)-1,2-bis(2-ethylhexyl) 3-nonyl 2-(pentanoyloxy)propane-1,2,3-tricarboxylate (COEV) and viscosity index (VI) at 195 for ester (2R)-1-decyl 3-(2-ethylhexyl) 2-heptan-3-yl 2-(propionyloxy)propane-1,2,3-tricarboxylate (CDEP). The stabilities of the prepared esters were confirmed via the computational analysis and their stabilities were ranked as CDEP > COEP > COEO > COEV.
ISSN:1040-2004
1547-397X
DOI:10.1080/10402004.2023.2269242