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

A series of noncommercial polyols which do not contain 13-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 H-1 and C-13 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 degrees 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 degrees 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 degrees 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. (C) 2014 Elsevier B.V. All rights reserved.