NEW CLASS OF ADDITIVES TO INHIBIT TREE GROWTH IN SOLID EXTRUDED CABLE INSULATION.

This report concludes the work the intent of which was the development of an additive that would inhibit tree growth in extruded dielectrics. Ferrocene (5 percent) inhibits treeing and raises the needle-plane breakdown voltage by approximately 100 percent. However, it is unstable (oxidizes) both in air and in the presence of dicumylperoxide. None of the antioxidants investigated stabilized ferrocene. A new ionic compound, alpha -bromolauric acid, has been found to be effective in steel-needle breakdown tests at 60 Hz. Although it is oxidatively stable, results suggest that its performance may be specific to systems where field enhancement occurs at iron imperfections. Ref.