Breakdown by Treeing in Epoxy Resins

Insulating materials can fail through internal growth of tree-like breakdown channels. These "trees" are commonly nonconducting hollow interconnecting tubules. Conduction in such trees occurs by small discharges. The paper describes a test for treeing resistance and considers the effects of electric stress, resin composition, cure, etc., on breakdown time for typical epoxy systems. The rank of materials in treeing resistance varies with stress and shows no obvious correlation with other breakdown properties.