Greatly enhanced temperature stability of eco-friendly polypropylene for cable insulation by multifold long-chain branched structures

An effective approach to sustainable development of electrical devices represented by power cables has been put forward as replacing prevailing cross-linked polyethylene (XLPE) insulation with recyclable polypropylene (PP) insulation. However, it remains challenges for PP-based insulation to balance inherent contradiction among mechanical toughness, thermomechanical strength and electrical properties. To address the problem, in this paper, triple conflicting targets of optimization are simultaneously achieved by introducing multifold H-shape long-chain branched (LCB) structures into impact polypropylene copolymer (IPC). The compatibility between PP matrix and elastomer is enhanced by PP-H-EPC structure, resulting in 13 % reduction in mechanical modulus at room temperature. The thermomechanical strength was also improved by PP-H-PP and EPC-H-EPC structures, leading to 82 % and 85 % reduction in deformation and creeping at 160 degrees C, respectively. Besides, compared to XLPE, the electrical properties in a wide temperature range and corresponding temperature stabilities were significantly improved under the combined effect of multifold LCB structures. Further results suggested the limited expansion of amorphous layer as the origin of improvement in electrical temperature stability. Evidently, the reported LCBIPC represents a promising alternative to XLPE insulation, which is believed to ease the production as well as recycling of power cables by combining advantages of thermoset and thermoplastic insulation.