Research on Properties of CB/EVA Semiconductive Shielding Composites

Abstract

In order to select suitable carbon black (CB) for manufacturing semiconductive shielding materials of XLPE insulated high voltage cable, the composites were prepared with the melt blending method by adding CB with different properties into ethylene/vinyl acetate copolymer (EVA). The volume resistivity, mechanical property and rheological property of the composites were measured. The effects of the properties and content of CB on the various properties of the composites were investigated and their mechanism was analyzed. The research results show that both structure and specific surface area of CB have great effects on the volume resistivity and rheological property of the composites. Because high structure CB usually has high specific surface area, the high structure CB/EVA composites have low percolation threshold and low rheological property. The EVA composites containing low structure CB with larger specific surface area exhibit low conductivity and high melt viscosity. When the mass fraction of CB with low structure and small specific surface area reaches 35%, the volume resistivity of the composites is approximately 100 Ω·cm and the rheological property of the composites is obviously superior to the composites filled with high structure CB. The CB with small specific surface area and low structure as conductive filler is beneficial for good conductivity and extrusion processability of the semiconductive shielding materials.