Synthesis and characterization of new esters of oleic acid and glycerol analogues as potential lubricants

Abstract A series of noncommercial polyols which do not contain β-hydrogen were used to synthesize new oleic acid based esters as potential thermally stable biolubricants. Commercial trimethylolpropane (TMP) was used to synthesize TMP trioleate as a reference polyol ester. The esters were purified by column chromatography and their structures were confirmed by 1 H and 13 C NMR and HRMS. The evaluated properties were kinematic viscosity, thermo-oxidative stability (by TGA) and melting point (m.p., by DSC). All the esters showed high viscosity indices (160–200) and similar thermo-oxidative stability ( T onset of triesters around 330 °C), but a small change in the structure of the triols could generate esters of different viscosity grades (ISO VG 46 and 68) and different m.p. (ranging from −15 to −35 °C). Two of the polyols generated triesters with virtually the same properties of TMP trioleate: pentaerythritil monoethyl ether (PEET) and pentaerythritil monobutyl ether (PEBUT). Two polyols must be highlighted: pentaerythritil monophenyl ether (PEPH) and trimethyloltoluene (TMT). PEPH generated an ISO VG 68 lubricant with a m.p. of −19 °C, relatively low for this class, and TMT generated an ISO VG 68 lubricant with no defined melting peak, suggesting it has better cold temperature flow properties than TMP trioleate.