Relationship between the Chemical Structure and the Effectiveness of Additives in Inhibiting Water-Trees

Phenomenological investigations of water trees showed clearly that their formation can be inhibited by additives. Stabilizers for concentrated solutions of H2O2 were found to be particularly effective. Based on this observation, a model of water-tree formation was postulated, which considers water treeing essentially as an oxidative degradation with electrochemical initiation at defects and at water/polymer interfaces. Based on this model numerous additives inhibiting water trees have been found, amongst them barbituric acid. This substance is amenable to numerous chemical modifications, and in this contribution the influence of the structural variation of barbituric acid derivatives upon water treeing is described. Depending upon the chemical structure, their effectiveness varies from complete inhibition of water trees on the one side to a complete lack of retardation on the other.