Effect of polyethylene on morphology and dielectric breakdown in EVA blends

Ethylene vinyl acetate (EVA) provides, potentially, a novel material for inclusion into high voltage cable insulation providing a degree of electrical conductivity, whilst at the same time avoiding the dispersion problems associated with conventional conducting polymers and fillers. Although this can decrease the dielectric breakdown strength and increase the dielectric loss of the material, the ability to suppress localised high electric fields (for instance around inclusions or at electrical tree growth sites) may help to prolong the service life of the insulation. In addition, routes are opened up to creating novel two-phase morphologies, which could have advantages relating to the control of electrical tree growth. The current study focuses on the crystallisation behaviour, morphology and dielectric breakdown of a number of polyethylene/EVA blends with a high EVA content. The morphology will be controlled by choosing different vinyl acetate contents and by varying the crystallization conditions. The relationship between the different morphologies and the electrical properties of the composite systems will be explored.