High-Performance Lubricant Base Stocks from Biorenewable Gallic Acid: Systematic Study on Their Physicochemical and Tribological Properties

Abstract

Synthesis, characterization, and evaluation of a series of gallate derivatives as lubricant base stocks are described. The gallate derivatives were synthesized via sequential esterification and alkylation reactions from biorenewable raw material gallic acid. All the synthesized gallate derivatives were structurally characterized by using NMR, IR, and HRMS spectral data. Their physicochemical and lubricating properties including density, viscosity, viscosity index, pour point, flash point, volatility, corrosion level, thermal and oxidation stability, and frictionreducing and antiwear properties were systematically investigated. On the basis of the physicochemical and lubricating data, it can be concluded that gallate derivatives have good properties in terms of viscosity−temperature characteristics, corrosion ability, volatility, and low-temperature flow ability. More important, they have predominant thermal and oxidation stability, as well as hightemperature friction-reducing and antiwear performances compared with the existing synthetic ester oils. These favorable technical performances together with their biological available resources recommend gallate derivatives as excellent base stocks for the development of high-performance green lubricant products.

Ester Oils Prepared from Fully Renewable Resources and Their Lubricant Base Oil Properties

“…For ester oils, increasing the branched chain leads to higher dependence of viscosity on temperature. 35 , 37 Besides, the introduction of branched chains can increase KVs, e.g., KV 40 (3C 8 –C i8 , 56.7 mm 2 /s) < KV 40 (3C i8 –C i8 , 149.4 mm 2 /s) and KV 100 (3C 8 –C i8 , 8.4 mm 2 /s) < KV 100 (3C i8 –C i8 , 13.4 mm 2 /s). The VIs of the gallate ester oils vary from 81 to 135, which are all higher than that of Phe–3C i8 (74).…”

“… 33 , 34 In our former work, high-quality synthetic esters were developed through chemical modification of naturally available 3,4,5-trihydroxybenzoic acid. 35 Although they were found to have high thermal and oxidative stabilities, excellent friction-reducing and antiwear properties at high temperatures. In view of environmental pollution and energy-saving issues, the developed esters still have defects of dependency on nonrenewable petroleum resources and inadequate biodegradability due to the presence of long alkoxy chains.…”

Lubricating properties of ester oil prepared from bio-based 2,5-furandicarboxylic acid

“…The physical adsorption films play a major role, while the chemical reaction (oxidation) films play a minor supporting role in the friction reducing and antiwear efficiency of the ester oils. The former was ultrasonically cleaned prior to XPS testing [46]. XPS testing was also performed on the steel and aluminum metal surfaces (as shown in Figs.…”

Comparison of the oxidation resistance of synthetic ester oils DOA and TDTM: Experimental evaluation and theoretical calculation

“…Synthetic esters, including di‐isooctyl adipate (DOA) and tri‐isodecyl trimellitate (TDTM), are one of the most important types of synthetic oil. Many outstanding properties (eg, high thermal‐oxidative stability, excellent lubricating property and biodegradability, low volatility, and low temperature fluidity) encourage the use of ester oils in many fields, including the aerospace and automotive industries . Currently, the increasingly harsh operating conditions of mechanical equipment, such as heavy loads and high speeds, result in elevated working temperatures in lubrication systems.…”

“…Many outstanding properties (eg, high thermal-oxidative stability, excellent lubricating property and biodegradability, low volatility, and low temperature fluidity) encourage the use of ester oils in many fields, including the aerospace and automotive industries. [1][2][3][4][5] Currently, the increasingly harsh operating conditions of mechanical equipment, such as heavy loads and high speeds, result in elevated working temperatures in lubrication systems. Consequently, the synthetic ester oil inevitably undergo thermal oxidation, especially under sustained high temperature.…”