Development of palm-based neopentyl glycol diester as dielectric fluid and its thermal aging performance ABSTRACTThe potential of palm-based neopentyl glycol diester as dielectric insulating fluid was investigated. The details of the transesterification of high oleic palm oil methyl ester (POME) with neopentyl glycol (NPG) with the final product yield of more than 90 wt% of NPG diester were discussed. The thermal aging performance of NPG diester was compared with conventional mineral insulating oil at 90, 110 and 130 °C. This paper focused mainly in the effects of aging to chemical, physical and electrical properties of NPG diester. Apart from being fully biodegradable and non-toxic, the synthesized diesters exhibited high flashpoint and the breakdown voltage was comparable to mineral oil. The result indicated that throughout the aging period, NPG diester exhibited lower acid value than mineral oil and no significant change in viscosity was observed. The study on mechanical properties of insulating paper aged in NPG diester shows higher tensile strength than paper aged in mineral oil. The synthesized esters have shown great potential to be used as transformer oil.

Methyl esters of coconut, palm kernel and palm oils were transesterified with 2-ethylhexanol, trimethylolpropane or neopentylglycol to produce monoester and polyol esters in this study. Experimental investigations were conducted to explore the thermal-oxidative characteristics and catalytic effects of copper/iron on monoester and polyol esters by using the turbine oil oxidation test. Thermogravimetric analysis and differential scanning calorimetry were also performed to evaluate the thermal and oxidation onset temperature. Among the structural trends that improved the oxidative stability include increasing carbon chain length and presence of monounsaturated as opposed to saturated fraction. The study revealed that the presence of copper accelerated the degradation of certain polyol esters. Also, polyol esters are found to be thermally more stable than mineral transformer oils.

Adaptation of apt chemical modifications and incorporation of suitable additives, especially, nano-additives, could improve the properties of bio-lubricants derived from palm oil. This makes it one of the best alternatives to mineral oil lubricants. Possible chemical modifications are hydrogenation, esterification/ transesterification, epoxidation and metathesis. Feasible additives and nano-additives available in the market for minimizing the drawbacks of palm oil as a lubricant are ionic liquids, phosphorus, sulphur, zinc dialkyl dithiophosphate, metal, metal oxides, metal sulphides, carbonates, borates, carbon materials, organic materials, hexagonal boron nitride, alumina, CaO, CuO, ZnO, TiO2 and lanthanum borates. Few of them may not be environmental friendly. In line with market potentials and demand, it could be predicted that ROI of funding for the research and development of palm oil as a bio-lubricant may be significantly high. The study addresses tribological performance and properties, chemical modifications and formulation with additives of palm oil as a bio-lubricant.

This article presents the experimental studies carried out on the environmental friendly polyol ester insulating liquids to investigate the effect of molecular structure on the physical, chemical, and electrical properties. Six different polyol esters that can be produced from the transesterification of various methyl esters with neopentylglycol/trimethylolpropane alcohols were synthesized and compared with those of refined, bleached, and deodorized palm oil (RBDPO) and mineral transformer oil. The finding suggests that the physical properties like fire point, pour point, and viscosity are very much affected by the molecular weight and molecular composition of the polyol esters. The electrical properties are also highly influenced by the molecular structure-related characteristics, such as the polarity, dipole polarization, carbon chain length, and degree of branching. The results confirm the findings of previous studies that the polyol esters and RBDPO have more polarity and dipole polarization compared to mineral oil. The experimental evidence showed that the newly synthesized insulating liquids have favorable thermal and electrical properties, thus suggesting that the insulating liquids have the potential to replace conventional insulating liquids to provide a more sustainable power system in the future.

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