Toward Eco-Friendly High Voltage Insulators: Enhancing AC Breakdown Strength of Epoxy Resin by Epoxidized Castor Oil

This study explored the development of epoxyepoxidized castor oil biocomposite as the potential biodegradable high voltage insulation alternative, aiming at addressing the environmental sustainability challenges posed by conventional petroleum-based epoxy resin insulators. Epoxidation of castor oil was conducted by an in situ method at varying times of 4, 10 and 16 hours to examine the influence of epoxidation degree on breakdown strength properties, while the biocomposites were prepared through a high-temperature curing method for ensuring dense crosslinking networks. The successful epoxidation of castor oil and its integration into the epoxy matrix were confirmed by Fourier Transform Infrared Spectroscopy (FTIR), while Scanning Electron Microscopy (SEM) and lowtemperature Differential Scanning Calorimeter (DSC) revealed the enhancement in surface homogeneity and crosslinking density respectively with an increase in epoxidation degree of castor oil. The relative permittivity and dielectric losses were examined by Novocontrol spectrometer whereby biocomposite samples demonstrated the decrease in both parameters as compared to pristine epoxy resin. Notably, the biocomposite comprised of 16 hours epoxidized castor oil at 40% weight relative to epoxy resin achieved a 9.6% improvement in breakdown strength scale parameter. These results revealed that the high-temperature cured biocomposite derived from highly epoxidized castor oil and epoxy resin offers the high-performing, eco-friendly alternative to conventional epoxy resin for highvoltage insulation applications.