High-temperature creep resistant ternary blends based on polyethylene and polypropylene for thermoplastic power cable insulation

The 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\ua0wt% SEBS significantly increases the storage modulus between the melting temperatures of the two polyolefins, 110 and 160\ub0C, 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 7 10 \ua0S m at 70\ub0C and 30 kV mm , 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