Effects of elastomers modified with polar molecules on water tree resistance of cross-linked polyethylene

The paper evaluated the water tree resistance of cross-linked polyethylene (XLPE) by using an elastomer modified with polar molecules. Samples containing maleic anhydride grafted poly[styrene-b-(ethylene-co-butylene)-b-styrene] (SEBS-g-Ma) have been prepared by melt compounding and subsequent compression molding, respectively. Accelerated water tree aging of the samples was carried out under the combined stresses consisting of ionic aqueous and high frequency electrical stress. The results showed that the introduction of SEBS-g-Ma could improve the water-tree resistance of XLPE. The length of water trees in XLPE/SEBS-g-Ma blends shows the best water-tree resistance as the SEBS-g-Ma content is 5phr (The term "phr" means parts per hundred of total polyethylene, by weight). Starting at 10phr, however, the length of water trees in the SEBS/XLPE-g-MA blends increases as the SEBS-g-Ma content increases. The samples were also evaluated by means of Gel content testing, mechanical measurement, dielectric measurement, and scanning electron microscopy (SEM) observation. It was found that SEBS-g-MA had little influences on the mechanical and dielectric properties of XLPE.