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Vegetable oil with high percentage unsaturated fatty acid content are unstable to oxidation at elevated temperatures. However, epoxidation is an effective chemical reaction for chemical structural modification of such oil to eliminate unsaturated carbon–carbon double bond which is responsible for the instability of the oil. In this research, laboratory purified neem oil was epoxidized in situ in the presence of an acidic catalyst and the product was further transesterified. The purified (PNO), epoxidized (ENO) and transesterified (ENOE) oil samples produced were characterized by FTIR, Viscosity measurement using Brookfield Digital Viscometer, relative permittivity, loss tangent and ac conductivity measurements were made using a coaxial probe placed in a thermostatically controlled heat chamber and a frequency analyzer at varying frequency and temperature in the range 20 Hz to 20 kHz and 20 °C to 70 °C respectively. All three samples show Arrhenius type behavior for viscosity and ac conductivity. ENOE sample had least viscosity of 0.0254 Pa s at 40 °C. Both PNO and ENO had a.c conductivity of the order 10 −10  S/m at 20 °C and power frequency and loss tangent of 0.0082 and 0.0191 respectively. The oil samples possess low loss in the temperature and frequency ranges considered and are suggested to be suitable candidate for potential natural ester insulating fluid in High Voltage equipment. [ABSTRACT FROM AUTHOR]

The exposure of polymeric insulation in nuclear power plants necessitates the study of the effect of neutron irradiation on the mechanical and dielectric properties of neat and nano-filled polymeric-based insulation materials. The exposure of the materials to ionizing radiation can influence their dielectric and insulating properties. This work presents the influence of neutron irradiation on the dielectric behavior of neat and nanoparticle-filled Epoxy-TiO 2 nanocomposite. The prepared neat and nanocomposite samples were exposed to neutron radiation in the Nigeria Research Reactor I (NIRR-I). The mechanical and dielectric analyses of the samples were performed before and after irradiation. The presence of 2 wt% TiO 2 nanoparticles in the epoxy matrix resulted in optimum mechanical and dielectric behavior. While the presence of the nanoparticles seems to have a significant influence on the reduction of the mechanical degradation of the composite (39.96%–12.11% after exposure to 4.5 kGy), it does not have much influence on the reduction of the dielectric loss of the composite. The variation of temperature of the sample revealed that the 2 wt% nanoparticles filled polymer displayed higher relaxation activated energy. The research suggests that the filling of the epoxy polymer with 2 wt% TiO 2 nanoparticles can modify the mechanical and dielectric relaxation behavior of the polymer composites. This could enhance the resistance of the composite material to the effect of radiation-induced degradation in the polymeric insulation. • Exposure of the polymer samples to neutron led to radiation-induced degradation. • Dispersion of 2 wt% nanofiller resulted in an improved tensile strength from 39.96% to 12.11%. • Lowest dielectric loss was obtained for with 2 wt% of the nanoparticle. • Temperature variation revealed relaxation activation energies. • 2 wt% TiO 2 nanoparticle shows optimum reinforcement effect in the epoxy. [ABSTRACT FROM AUTHOR]

Abstract: This report presents a method for synthesizing base-stock for green industrial product from a vegetable oil with a high composition of unsaturated fatty acids. Epoxy methyl ester of palm kernel oil was synthesized from laboratory purified palm kernel oil using a two-step reaction and the products were used as a base-stock for green electrical insulation fluid. Epoxidized palm kernel oil was first prepared through epoxidation reaction involving purified palm kernel oil, acetic acid and hydrogen peroxide in the presence of amberlite as catalyst which lasted for 4h. It was then followed by transesterification reaction involving the epoxidized product and methanol in the presence of sodium hydroxide as catalyst to synthesize the corresponding epoxy methyl ester. The thermal and electrical breakdown properties of the epoxy methyl ester demonstrated significantly improved properties for its use as raw material for bio-based industrial products such as electrical insulation fluids. [ABSTRACT FROM AUTHOR]

Mineral oil has been serving well as a cooling and insulation oil in high voltage power equipment but with a setback when considering environmental friendliness whenever there is spillage due to its poor carbon profile. Several works have been done on the enhancement of dielectric properties of green alternative with different nanoparticles but little attention was placed on its cooling properties which is one of the major functions of the oil. Also, to prevent food competition, esters from a non-edible seed oil should be given more consideration. This work, therefore, investigates the cooling properties of synthesized insulating nanofluid using Neem oil ester as the base fluid together with (Insulating) SiO 2 and (semiconductive) WO 3 nanoparticles. The nanoparticles were characterized using FTIR and XRD to confirm their functional groups and crystallite size respectively. Transesterification of the oil was done using sodium methoxide and the nanofluid samples were prepared by dispersing the nanoparticles into the oil. The nanoparticles were varied from 0.2 wt% to 1 wt%. The pour point, flash point and viscosity were measured according to ASTM standards. An increase in the pour point, flash point and viscosity were observed at every loading of the nanoparticle. The nanofluid with dispersed SiO 2 nanoparticles were observed to possess superior properties as a cooling liquid in high voltage power equipment when compared with the fluid with WO 3 nanoparticles because of its low viscosity, low pour point and good flash point. After the ageing, the synthesized fluids still retained their properties which is better than the mineral oil. • The influence of SiO 2 and WO 3 nanoparticles on the physical properties of the Neem oil ester was examined. • The two nanoparticles enhance the Flash point of the Neem oil ester. • An increase in the pour point of the Neem oil ester was observed through addition of the two nanoparticles. • A slight increase in the viscosity of Neem oil ester was observed after the addition of the particles. • After ageing of the nanofluids, the viscosity of the nanofluid was found better than the viscosity of the aged mineral oil. [ABSTRACT FROM AUTHOR]

The effect of neutron irradiation on the impedance of the nano-filled polymeric based insulation materials became an important issue because of its presence in the nuclear power plant. The exposure of polymeric materials to ionizing radiation can influence the dielectric and insulating properties of the material. This work presents the influence of neutron irradiation and the presence of nanoparticle on the insulating property of Epoxy-TiO 2 nanocomposite. The prepared plane nanocomposite samples were exposed to neutron radiation in the Nigeria Research Reactor I (NIRR-I) and dielectric analysis was performed over a frequency range of 20 Hz–200 kHz. The polarization relaxation process of the irradiated neat and nanocomposite is dominated by dipolar, interfacial polarization, and free radicals. The presence of TiO 2 nanoparticles in epoxy composite resulted in improved impedance after irradiation when compared with the non-irradiated and irradiated neat polymer. The 1 wt% nano-filled polymer has higher impedance after irradiation and followed by the 2 wt% nano filled polymer. The impedance of the irradiated 1 wt% TiO 2 nano-filled epoxy polymer increased by 8.3% and 160% when compared with the non-irradiated and irradiated neat epoxy polymer respectively. The variation of temperature of the sample revealed a consistent thermally activated process in the irradiated samples. The research suggests that filling the epoxy polymer with 1 wt% TiO 2 nanoparticle can modify the dielectric and the polarization relaxation behaviour of the polymer composites. This could enhance the resistance of the polymer composite to radiation-induced degradation in the polymeric insulation. • Exposure to neutron produced free radicals that led to a 57.4% decrease in impedance. • Dispersion of 1 wt% nanofiller resulted in an improved impedance after irradiation. • Increasing filler content introduced more space charges in the polymeric insulation. • Temperature variation shows thermally activated process in the irradiated samples. • 1 wt% TiO 2 nanoparticle enhanced radiation-induced degradation resistance in the epoxy. [ABSTRACT FROM AUTHOR]

In the last decades, vegetable-based insulating liquids, derived from plant seeds, have emerged as an environmentally friendly alternative to traditional petroleum-based mineral insulating oils. These vegetable oils exhibit excellent characteristics for high-voltage insulation, including remarkable high-temperature stability, as evident in their flash and fire points. Furthermore, their high water absorption capacity may serve to safeguard the integrity of paper insulation within transformers. However, their practical application is limited to sealed transformers due to their susceptibility to oxidation. Additionally, using these oils in regions with low temperatures presents challenges because of their poor flow properties under cold conditions. Canola oil, derived from canola seeds, offers a balanced set of properties, particularly concerning pour point and oxidation stability, attributable to its unique fatty acid composition. This study reviews deeply into the potential, prospects, and possible enhancements that can be applied to canola oil. Significant tutorial elements as well as some analyses are included. The aim is to reveal the deep attributes of canola oil as a suitable insulating liquid for both free-breathing and hermetically sealed transformers, while also ensuring it serves as an efficient cooling medium for transformers operating in extremely cold environments. Of the many properties examined, this review pays particular attention to oxidation stability and the flow characteristics of the oil. • Plant-based insulating liquids are environmentally friendly and sustainable. • Canola oil is a potential alternative to mineral-based insulating liquids. • Cooling and oxidative stability enhancement of plant-based oil for insulation. • Useful life, recyclability, and advantage of canola oil in transformer insulation. [ABSTRACT FROM AUTHOR]

A clean alternative insulating oil has been the quest of researches over the years due to non-degradability of mineral oil and safety issues. With the application of nanoscience and nanotechnology, the potential of transformer oil-based nanofluids has been thoroughly investigated with signs of significant improvement. Attention was placed on natural ester as a green alternative and it was realized that it has the potential to become a replacement for mineral oil. However, for natural ester-based nanofluids, the performance analysis is not well explored and there is still room for more investigations. This paper focused on the improvement of the physicochemical properties, dielectric loss and breakdown voltage of palm kernel oil ester using Al 2 O 3 and TiO 2 nanoparticles. The nanoparticles were characterized using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and Scanning electron microscopy (SEM) equipped with electron dispersive X-ray analysis (EDX). The physicochemical properties, relative permittivity, dielectric loss, and high voltage DC conductivity of the nanofluid samples were studied with varying weight percentages of Al 2 O 3 and TiO 2 nanoparticles ranging from 0.2 wt% to 1 wt% in a step of two to understand the behaviour of the materials. The adequacy of the fluid samples as an electrical insulating fluid in oil-filled high voltage (HV) electric equipment was explored and compared. For both types of nanoparticles, the dielectric loss was observed to decrease at 1 wt% but with a more noticeable decrease when considering Al 2 O 3 nanoparticle. Measurement of DC electrical breakdown voltage of the ester-based nanofluids revealed that the dispersion of nanoparticles in the fluid result in an increase in the breakdown voltage of the base fluid with the optimum value obtained at 0.6 wt%. The study indicated a decrease in the dielectric loss of the nanofluid sample and exhibited improved breakdown voltage when compared with the base alkyl ester. Image 1 • Examine the influence of nanoparticles on the properties of ester insulating fluid. • The nanoparticles enhances the physicochemical properties of the fluids. • The nanoparticle dispersion led a decrease in the dielectric loss. • Optimum DC breakdown voltage was observed at 0.6 wt% for Al 2 O 3 and TiO 2 nanofluid. • The study confirmed that Al 2 O 3 nanofluids will serve well as an insulation fluid. [ABSTRACT FROM AUTHOR]

• The influence of nanoparticles on the dielectric properties of neem oil was investigated. • Dielectric properties of the base liquid increases with nanoparticles loading. • Effect of temperature on the dielectric loss of the nanofluids was investigated. • The compatibility test of the nanofluid with kraft paper was investigated. • Nanofluid has no pronounce effects on the dielectric properties of kraft paper. Methyl ester from vegetable oil has been considered a potential replacement for mineral oil used for power transformer cooling and insulating applications. However, some pertinent properties in making this liquid a better transformer oil based on the laydown standards need to be enhanced to maximize the use of this insulating liquid. Technology involving nano-modification can enhance the properties of these ester liquids placing them in a better position as a good alternative. In this study, we aim to investigate the performance of methyl ester liquid from neem seed oil, a non-food grade oil, when modified with SiO 2 insulating nanoparticles at several concentrations. Furthermore, Kraft paper compatibility has also been analyzed to observe their compatibility after impregnation. The breakdown strength, temperature-dependent dissipation loss factor, dielectric constant, and viscosity of both pure and nanofluid samples of neem ester liquid have been measured per standard methods. The nanofluid's dielectric performance has been significantly enhanced by the presence of SiO 2 nanoparticles according to results obtained from the experiment. For instance, the dielectric dissipation factor at an operating frequency of 60 Hz has been improved by 96%, 89%, and 79% at 30 °C, 50 °C, and 70 °C respectively relative to the base neem liquid. This remarkable improvement has been attributed to the SiO 2 nanoparticle's ability to polarize, trap, and de-trap mobile electrons develop in nanofluid when an electric field is applied. [ABSTRACT FROM AUTHOR]

• The influence of nanoparticles on the dielectric properties of neem oil was investigated. • Dielectric properties of the base liquid increases with nanoparticles loading. • Effect of temperature on the dielectric loss of the nanofluids was investigated. • The compatibility test of the nanofluid with kraft paper was investigated. • Nanofluid has no pronounce effects on the dielectric properties of kraft paper. Methyl ester from vegetable oil has been considered a potential replacement for mineral oil used for power transformer cooling and insulating applications. However, some pertinent properties in making this liquid a better transformer oil based on the laydown standards need to be enhanced to maximize the use of this insulating liquid. Technology involving nano-modification can enhance the properties of these ester liquids placing them in a better position as a good alternative. In this study, we aim to investigate the performance of methyl ester liquid from neem seed oil, a non-food grade oil, when modified with SiO 2 insulating nanoparticles at several concentrations. Furthermore, Kraft paper compatibility has also been analyzed to observe their compatibility after impregnation. The breakdown strength, temperature-dependent dissipation loss factor, dielectric constant, and viscosity of both pure and nanofluid samples of neem ester liquid have been measured per standard methods. The nanofluid's dielectric performance has been significantly enhanced by the presence of SiO 2 nanoparticles according to results obtained from the experiment. For instance, the dielectric dissipation factor at an operating frequency of 60 Hz has been improved by 96%, 89%, and 79% at 30 °C, 50 °C, and 70 °C respectively relative to the base neem liquid. This remarkable improvement has been attributed to the SiO 2 nanoparticle's ability to polarize, trap, and de-trap mobile electrons develop in nanofluid when an electric field is applied. [ABSTRACT FROM AUTHOR]