Generation of free radicals in electrical trees

This paper reports recent results in a continuing ESR study of free radicals in electrical trees in polyethylene (PE). Data pertaining to three different kinds of PE are presented: commercial cable material (XLPE), and two low density materials (LDPE), one relatively impure, the other of high purity (HPPE). It is found that the saturation behavior of the absorption lines is particularly useful for distinguishing different physical situations. On the basis of these observations, a preliminary classification with respect to the degree of carbonisation of char produced in different kinds of trees is proposed.