An investigation into morphological changes in water treed LDPE

For water treeing, key structural details include: size, density, and connectivity of voids; where changes occur; changes of crystallinity; and molecular weight of polymer chains. The authors describe how different treatments affect treeing appearance, and relate these to porosity measurements and to DSC and NMR examination of possible chain breakage or crystallinity changes. Water trees were grown in 0.8-mm-thick LDPE (low-density polyethylene) sheets using either LiCl or FeCl₃ solutions of 0.5 M/l concentration. The observed effects of the different treatments on the water trees are most likely due to some combination of chain breakage during treeing and the escape of strongly bonded water. However, consideration of the sensitivities employed means that the possibility of some reduction in crystallinity cannot be ignored