Plastics are used extensively in the manufacture of electrical items, such as circuit boards and electrical cables. These applications can be harsh, exposing the plastic to a mixture of thermal, chemical and electrochemical attack. Many electric items like transformers, microprocessors or high-voltage cables operate at elevated temperatures for years, or even decades, resulting in low-level but continuous thermal oxidation. This can be exacerbated by direct contact with metals, which can promote the formation of free-radicals, for instance, by the action of Fenton reactions on hydroperoxides. High voltage loads can also damage insulating materials such as dielectrics, which degrade via electrical treeing caused by prolonged electrical field stress.