Toward Semi-Conductive Polyethylene/Ethylene Vinyl Acetate Copolymer Blends Filled With Carbon Black: Correlation With Microstructure

Abstract

Polyethylene (PE)/ethylene vinyl acetate (EVA) blends filled with carbon black (CB) is widely desired to fabricate semi-conductive systems, especially as a shielding layer that discharges electrical charges and uniforms the electric field in medium and high voltage cables. Addressing key challenges in formulating PE/EVA/CB blends influencing microstructure and thus performance, the present research comprehensively investigates the effect of CB content (0, 5, 10, 15, and 20 wt.%) and blend composition on the electrical and thermo-mechanical properties. The microstructure of the blend systems was analyzed using scanning electron microscopy (SEM) in relation to linear viscoelastic rheological assessments. Rheological studies revealed the formation of an incomplete network between CB particles in the blend systems, where they exhibited semi-conductive electrical properties. This was observed for the 50/50 blend sample, which displayed a co-continuous morphology, with CB content in the range of 10–15 wt.%, while other blend systems differing in blend morphology or CB microstructure were either insulating or conductive. In contrast to the PE phase, the crystallinity characteristics of the EVA phase were affected by a significant amount of CB (15 wt.%). CB served as a reinforcement for the tensile mechanical properties, and this impact was somewhat more pronounced in blends with higher amounts of EVA.