On the Mechanism of Treeing Inhibition by Additives in Polyethylene

On the basis of the experimental observation that the conductivity of acetophenone-doped polyethylene is field dependent over a range of applied electric stresses, a simple analysis shows that the increase in resistance to electrical treeing by additives is associated with this field-dependent conductivity. The additives can be considered as weak electrolytes. The rate of their dissociation into positive and negative charge carriers which causes an increase in conductivity is field dependent. A model for the behavior of the additives which leads to the lowering of the electrical stress at sites of high and divergent electrical stresses is given. Presently available experimental results are in good agreement with our proposed theory. Other factors affecting this mechanism are also discussed.