Electrical and Degradation Properties of Epoxy Insulating Materials Based on Schiff Bases

Epoxy is widely used as an insulating material for electric power and electronic equipment due to its excellent physicochemical properties and electrical performance. However, its stable 3D cross-linked structure makes it difficult to degrade and efficiently recycle. Epoxy insulation equipment is often incinerated or landfilled after decommissioning, resulting in environmental pollution and the waste of resources. Aimed at the demand of degradable epoxy insulating materials for power equipment, an epoxy with high insulation strength, low dielectric loss, and good thermal stability based on a Schiff base was designed and prepared in this paper. The vanillin and epichlorohydrin were etherized to produce an aldehyde-containing monocyclic oxide (VE), and the preparation process was optimized. After curing with a diamine curing agent at different temperatures, it was found that the content of Schiff base in epoxy first increased and then decreased with the curing temperature. The thermal, electrical, and degrading properties of epoxy vary with the Schiff base content. The maximum glass transition temperature is 121 °C, and the breakdown field strength gets its maximum of 45.4 kV mm–1, which is higher than that of conventional epoxy. The dielectric loss is comparable to that of conventional epoxy with the lowest of 5 × 10–3. Meanwhile, the epoxy can be completely degraded within 40 min in a mildly acidic environment, and the cast copper winding can be effectively recycled after degradation. This study can provide theoretical guidance for the application of degradable epoxy based on Schiff base to insulating materials in power equipment.