Synthesis of trimethylolpropane fatty acid triester as a high performance electrical insulating oil

The trimethylolpropane esters (TME) based high performance electrical insulating oil was synthesized by esterification of the mixture of C 6 , C 8 and C 10 acids blend with trimethylolpropane (TMP). The conversion yields of TME is maximized at catalyst (SnCl 2 ) dosage of 0.8 wt.% and the TMP:acid molar ratio of 3.2:1 at 140 °C. 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 (23.3 mm 2  s −1 ) and much enhanced AC breakdown voltage (72.6 kV) comparing with the commercial natural ester insulating oil FR3® (34 mm 2 s −1 and 63 kV). The high performance of the insulating oil is also manifested by quite low pour point (−45 °C) and high flash point (248 °C) which are superior to those values of mineral insulating oil (−30 °C and 170 °C). The remarkable oxidation stability of the insulating oil is metered by the oxidation induction time (OIT) 2275 min at 130 °C which should be attributed to the elimination of C C double bonds and β-H atoms.