The diffusion of ions in polyethylene

It was demonstrated that inorganic ions dissolved in water which is in contact with polyethylene will diffuse into the polyethylene. Not all ions were found to diffuse at the same rate. It was also found that polyethylene in contact with salt solutions will absorb water, with more water being absorbed as the salt concentration is increased. The diffusion was found to be accelerated under basic conditions and inhibited under acidic conditions. Cross-linking of the polyethylene was found to slow diffusion. It is proposed that ions enter the polyethylene via certain `trapping´ sites without or with only a portion of their hydration sphere. These ions would then diffuse through the polyethylene film by hopping from one trapping site to another. All the results observed are compatible with the observations made on water treeing and advance the understanding of water tree formation