Susceptibility to endosmosis of electrical insulation

Two recent foreign publications have openly drawn attention to a type or, rather, class of failures which may beset electrical insulation, particularly wire and cable insulation: electro-endosmosis. Such failures are possible, and possible only, if the circuits operate on direct current, with the conductor at negative potential, and if the circuits are installed in moist locations. As usual, increased temperature accelerates the rate of deterioration but what other factors contribute to, or counteract, failure development is still fairly obscure. Most of the work has centered around polyvinyl-chloride compounds, and there seems to be little doubt that fatty acid ester plasticizers, and traces of emulsifiers, lower the resistance to endosmosis. On the other hand, polyvinyl-chloride compounds, as well as other insulations which are, for all practical operating conditions, immune to endosmosis, do exist.