A physico-chemical investigation of the possible causes of water treeing

Relationships between ion penetration, oxidation, and water tree growth in low-density polyethylenes (LDPE) and cross-linked polyethylenes were studied. Fourier transform infra red (FTIR) spectra showed that some oxidation had occurred but that the distribution was not homogeneous. Low-energy electron loss spectroscopy (LEELs) showed no indication of oxidation. The form and extent of trees developed depended on the nature of the electrolyte solution. Concentration profiles obtained by neutron activation analysis (NAA) indicated that the degree of ion penetration is species-dependent. Thermally stimulated creep (TSCr) spectra indicated that changes in the mechanical behavior of the polymer were dependent on the ions present and were probably due to a plasticization by water molecules. Thermally stimulated discharge current (TSDC) spectra obtained from heavily treed material showed ion-specific behavior that may be linked with structural changes within the polymer