Adipates of poly(propylene oxide-co-tetrahydrofuran) as a novel base stock for varied lube applications

Abstract

Three biodegradable polyalkylene glycols containing 1:1, 1:2 and 1:4 mol% fraction of propylene oxide and tetrahydrofuran were synthesized and denoted as 1,1-PTH, 1,2-PTH and 1,4-PTH. The synthesized polyalkylene glycols were subsequently treated with adipic acid to get desired esters. At first, three different copolymers of propylene oxide and tetrahydrofuran, namely 1,1-PTH, 1,2-PTH and 1,4-PTH (polyglycol containing 1:1, 1:2 and 1:4 mol% fraction of PO and THF), with molecular weights 564.0, 838.6 and 1070.7 were synthesized. Then, the esterification of the synthesized polyglycols was carried out using p-toluenesulfonic acid as the catalyst and toluene as a solvent. The obtained esters 1,1-PTHAD, 1,2-PTHAD and 1,4-PTHAD were observed to have the molecular weights 1292.1, 1705.0 and 2201.1, respectively. After molecular and physicochemical characterizations, the tribological properties were also evaluated. A comparison of the properties of these esters was made, and it was found that 1,1-PTHAD, 1,2-PTHAD and 1,4-PTHAD are favorably used as metalworking fluid, industrial gear oil and compressor lubricant base oil, respectively.