The role of oxidation in the water treeing progress in low density polyethylene (LDPE)

In an attempt to understand ion specific properties and the significance of oxidation in the water treeing process, an experimental examination of oxidation and tree growth in LDPE has been undertaken. In a series of water tree growth tests, conditions promoting oxidation were present either during or prior to tree development. FTIR (Fourier-transform infrared) techniques were employed to assess any oxidation occurring during tree growth in samples aged in the laboratory using ionic solutions of FeCl/sub 3/, KMnO/sub 4/, or LiCl. The lengths of trees grown in virgin and pre-oxidized LDPE using a LiCl solution have been compared. Neither enhanced tree growth nor significant oxidation was observed for LDPE samples aged in strong oxidizing solutions of FeCl/sub 3/ and KMnO/sub 4/. This shows that oxidation is not responsible for the observed tree growth characteristics. Reduced water tree growth was observed in highly oxidized material, indicating that the presence of such material is not significant in the water treeing process and that thermal oxidation alone is unlikely to be important during treeing.<>