Synthesis of Trimethylolpropane Esters as Potential Insulating Oil Base Stocks

The trimethylolpropane esters (TME) based high performance electrical insulating oil was synthesized by esterification of the mixture of C6, C8 and C10 acids blend with trimethylolpropane (TMP). The electrical performance is significantly improved by a purpose-oriented purification process which is structured by washing with ultrapure water and absorption with molecular sieve. The obtained insulating oil shows much reduced viscosity (25.6 mm²/s) and much enhanced AC breakdown voltage (72.6 kV) comparing with the commercial natural ester insulating FR3® (38.9 mm²/s and 65 kV). The high performance of the insulating oil is also manifested by quite low pour point (-45°C) and relative high flash point (240°C). The remarkable oxidation stability of the insulating oil is metered by the oxidation induction temperature (OIT) 203°C which should be attributed to the elimination of C=C double bonds and $\beta$-H atoms.