Comparison of Water Treeing Rates in Steam and Nitrogen Treated Polyethylenes

Water tree growth rates were measured at power frequency on compression molded plaques of nolyethylene, polystyrene and epoxy from water electrodes of controlled geometry. In spite of large changes in microvoid density, no significant differences in water tree growth rates were detected between steam and nitrogen treated polyethylenes. Water tree growth was followed for over 6 months in both polyethylene and polystyrene. No water trees could be detected in epoxy under the same conditions. Results are discussed in the light of DSC and TMA thermograms.