Greener Grids: Bio-Derived Epoxies for Next-Generation HV Insulation

Traditionally petroleum-derived materials based on Bisphenol A (BPA) have been used ubiquitously in high voltage components such as bushings, transformers and connectors due to their excellent electrical, thermal and mechanical performance. However, in recent years BPA and its analogues have raised significant health and environmental concerns. BPA is a toxic endocrine disruptor, whose high chemical stability means end-of-life disposal is problematic, in addition to its petrochemical origin.

Epoxidized vegetable oils (EVOs) and glycidyl ethers (GEs) present a promising alternative to these traditional epoxies. These plant oil derived materials are obtained from bio-feedstocks such as soybean, linseed and other plant oils. In addition to their renewable source, they tend to be non-toxic and biodegradable in controlled conditions, opening new opportunities for only for end-of-life management. Much of the research surrounding this variety of materials is in the composites space, therefore there is a distinct lack of electrical characteristics of these materials to determine their viability as a greener HV-insulation material.

This paper presents the production and characterisation of two of these bio-derived resins, epoxidized soybean oil (ESO) and glycerol diglycidyl ether (GDE), with respect to their electrical breakdown, curing and mechanical properties. The bio-resins exhibit a consistent characteristic breakdown strength (α: 25 - 30 kV/mm) across repeated batches of materials and a range of mechanical performances (E Modulus: 2.6 - 5.8 MPa) than can be tuned by monomer selection (ESO or GDE) and curing temperature (120 and 160°C).