Electric conduction in polyethylene between conductive fluid electrodes

It is well known that most fluids of low viscosity are penetrable into polyethylene and that some fluids such as acetophenone and silicone oil used as additives have the capability of inhibiting tree initiation or growth in polyethylene. Additives having such a capability are attractive to the insulation industry because the inhibition of tree initiation or growth implies the extension of the service life of polymeric-insulated apparatus and systems. It is generally believed that trees are initiated in the regions of highly localized electric fields, and that the action of additives is a stress-grading process activated either by field-enhanced dissociation [1,2] or by field-enhanced ionization [3,4]. Although such a stress-grading mechanism has long been used to elucidate the tree inhibition phenomenon, it is not unique and also not consistent with other features related to this phenomenon, indicating that a clear understanding of the behaviour of additives in polyethylene still remains to be obtained. To examine the stress-grading mechan2sm and to probe other more appropriate mechanisms, we have carried out an investigation into this problem from a different angle by studying electric conduction in polyethylene between conductive fluid electrodes in the hope that this would provide further insight into the behaviour of additives in polymers.