Morphological effect on high-voltage insulation properties in polypropylene/elastomer binary blends: An experimental and simulation study

• Lower mixing temperatures yield smaller POE domains, enhancing resistivity and BDS. • Simulations and experiments show smaller POE domains increase BDS. • Simulations also show smaller POE domains reduce field imbalance and space charge. Polypropylene (PP)/elastomer blends have been widely studied as promising insulation materials for high-voltage (HV) power cables. Among various factors, the size of elastomer domains critically influences their electrical insulation performance, such as resistivity and breakdown strength (BDS). However, this relationship remains poorly understood. This study investigates the effect of the polyolefin elastomer (POE) domain size on the high-voltage insulation properties of the PP/POE blend. The binary blends were prepared through melt-blending of the PP and POE at the different mixing temperature from 185 to 235 °C. As an increase of the mixing temperature, the size of dispersed POE domain was linearly increased due to the viscosity differences between the PP and POE. In addition, the tensile strength, elongation, volume resistivity, and DC breakdown strength were decreased with mixing temperature, which were thus correlated with the POE domain size. The BDS values derived from simulations were consistent with those calculated via the Power law equation, showing a decline in BDS with increasing mixing temperature. Analysis of electric field distribution and space charge accumulation indicated that smaller POE domains more effectively mitigate electric field imbalances, delaying BD compared to larger domains. This study highlights the significant role of morphology in determining the insulation performance of polymer blends, providing valuable insights for the design of HV insulation materials.