Polyethylene/styrenic block copolymer blends: Morphology and dielectric properties

In this work, a polymer blend of High Density Polyethylene HDPE and Styrene-Ethylene-Butylene-Styrene SEBS triblock copolymer has been prepared. The composition of the blend was tailored to control the morphology from a state of dispersed droplets of SEBS in a PE matrix to a fiber-like morphology. The microstructure of the blends has been assessed by means of Scanning Electron Microscopy SEM. The Thermal Gravimetric Analysis TGA has been performed on the samples to evaluate their thermal stability. The materials dielectric response was evaluated using Broadband Dielectric Spectroscopy BDS and the AC dielectric strength has been estimated by means of short-term breakdown tests. Overall, an improvement of the thermal stability of HDPE has been induced in the blend containing respectively 10 and 20 wt% of SEBS in droplets form. Moreover, the AC breakdown strength and the dielectric loss of this blend configuration remained in the same range of the pure HDPE. However, a consistent decrease of the AC dielectric strength, by approximately 13%, has been induced in the blend with a fiber-like morphology.