Water and Ion Absorption by Polyethylene in Relation to Water Treeing

Water absorption by polyethylene (PE) is discussed in relation to water treeing. Two steps have been considered: the first is water diffusion into undamaged PE, the second is water migration into growing water-tree channels. A critical discussion of published data is presented. Diffusion of water and Na+ ions into a low density PE film is studied by a radiotracer method in the absence of water-treeing. Na+ permeation is found to be very low (P < 4x10-15 cm2/s). A water permeability of 4.5x1O-10 cm2/s has been measured and is not affected by an applied uniform dc or ac electric field.