XLPE – layered silicate nanocomposites for high voltage insulation applications: dielectric characteristics, treeing behaviour and mechanical properties

The study presented here investigates the performance of nano‐reinforced cross‐linked polyethylene (XLPE) for high‐voltage insulation applications with particular focus on dielectric characteristics, treeing behaviour and mechanical properties. The nanocomposites with varying content of organo‐modified layered silicate (nanoclay) were prepared by melt mixing of polyethylene, cross‐linking agent and nanoclay. X‐ray diffraction and atomic force microscopy studies showed that layered silicates were uniformly dispersed with exfoliation in XLPE matrix up to 5 wt% nanoclay content with formation of intercalated structures with slight agglomeration at higher nanofiller content. The dielectric loss, relative permittivity and dielectric strength of the nanocomposites increased with increasing nanoclay content, which was attributed to the inherent properties of XLPE and nanoclay, nanofiller dispersion and interfacial polarisation. The effect of frequency on the dielectric properties was also investigated. Incorporation of nanoclay in XLPE altered the electric field stress distribution in the material and consequently retarded water tree growth. The electric field distribution and the probability of water tree growth were studied by finite element method. Additionally, mechanical properties of the nanocomposite viz. tensile strength and modulus were also enhanced. The changes in the properties were correlated to the morphology of the nanocomposites, as well as polymer filler interactions.