The influence and mechanism of elastomer types on electrical and mechanical properties of polypropylene insulation materials for high voltage cables

Polypropylene (PP) becomes a superior candidate material for new environmentally friendly cable main insulation with its excellent heat resistance, electrical properties, and degradability. However, in practical application, PP material is aging and vulnerable and its toughness is poor. The mechanical properties of PP material can be improved by elastomer modification, but the effects of different elastomers on the comprehensive properties of composite specimens are quite different. In this paper, the electrical and mechanical properties of different types of elastomer-modified PP composites are compared and analyzed by combining experimental and molecular simulation (MS) methods. The experimental results show that the SEBS/PP composite material has the lowest trap energy levels among all kinds of composite materials, its space charge accumulation is 1.96 × 10⁻⁹C, and the mechanical and rheological properties improvement of the composite is the most remarkable. Meanwhile, the volume resistivity is reduced by two orders of magnitude compared with pure PP. However, the breakdown strength of all kinds of composite materials decreases by different degrees after the modification. The solubility parameters (δ) and the free volume are further investigated by the molecular simulation, which shows that the δ of SEBS is similar to that of PP, which represents the best compatibility. Moreover, the SEBS/PP composite material has the strongest inter-molecular force and the most excellent toughness improvement for PP. This work provides a theoretical basis for elastomer selection in PP modification.