AbstractThe impact of a small amount of polystyrene‐b‐poly(ethylene‐co‐butylene)‐b‐polystyrene (SEBS) on the thermomechanical and electrical properties of blends comprising low‐density polyethylene (LDPE) and isotactic polypropylene (PP) is investigated. SEBS is found to assemble at the PP:LDPE interface as well as within isolated PP domains. The addition of 10 wt% SEBS significantly increases the storage modulus between the melting temperatures of the two polyolefins, 110 and 160°C, and results in improved resistance to creep during both tensile deformation as well as compression. Furthermore, the ternary blends display a very low direct‐current (DC) conductivity as low as 3.4 × 10⁻¹⁵ S m⁻¹ at 70°C and 30 kV mm⁻¹, which is considerably lower than values measured for neat LDPE. The here presented type of ternary blend shows potential as an insulation material for high‐voltage direct current power cables.