Tunable morphology and resistivity of ternary polymer composites of carbon black/low density polyethylene/ethylene‐vinyl acetate with carbon blacks having different surface properties

Abstract Medium to extra‐high voltage electrical cables typically comprise a semiconductive polymer composite layer to homogenize the electromagnetic field through the cables. The semiconductive layers usually contain a high content of carbon black (CB) for reduced electrical resistivity. In this study, we found that both the morphology and resistivity of a ternary polymer composite of CB/low density polyethylene (LDPE)/ethylene‐vinyl acetate (EVA) depend on CBs used and the order of addition. Three types of CB were investigated. CB‐A, which has the lowest surface energy and the most uniform surface energy profile, exhibits a strong affinity to LDPE and always segregates in the LDPE phase whether it is first added in the LDPE phase or the EVA phase. CB‐B and CB‐C, which have higher and less homogeneous surface energies, distribute differently with different orders of addition. We observe a significant reduction in the percolation threshold of CB‐A in the CB/LDPE/EVA composite, but not with CB‐B or CB‐C. Adding CB‐A in the LDPE phase first results in substantially lower resistivity than adding it in the EVA phase first, whereas adding CB‐B or CB‐C in the LDPE phase first results in higher resistivity than adding them in the EVA phase first.