Water-tree growth in styrenic dielectrics

While water trees have been of most concern to the users and suppliers of high voltage underground cable, the phenomenon can be expected to occur in any polymeric dielectric exposed to a sufficiently high electrical stress in the presence of moisture. Water trees have been reported in number of materials including polyvinyl chloride), epoxy, polycarbonate, polystyrene and silicone rubber(1). As this list illustrates, water trees can occur in a variety of materials with large differences in chemical constitution, super-molecular structure, and physical state.