The polymer-water interaction in water treeing: an NMR study

The polymer-water interaction in polyethylene was investigated to establish whether water enters into chemical reactions with the polymer during water tree growth, determine the physical state of water in water trees, and study the effects of sample composition on tree growth. The extent of chemical interactions with the polymer was investigated by deuterium (isotope effect) and high-resolution solid-state carbon-13 NMR for water trees grown in D₂O and H₂O. The physical state of the water within the water trees was investigated by NMR relaxation time measurements. The results indicate that: (1) chemical interactions are not the dominant factors in water treeing; (2) the water in the treed polyethylene does not exist in the bulk in large cavities or microscopic channels, and there exists different environmental states of water in trees; (3) antioxidant additives and crosslinking do not greatly affect water tree growth