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

Abstract

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.

Hierarchical Structural Evolution, Electrical and Mechanical Performance of Polypropylene Containing Intrinsic Elastomers under Stretching and Annealing for Cable Insulation Applications

“…To address the emerging challenge, a growing body of research on PP insulation materials has been conducted to balance their thermo-mechanical and electrical performance. The main modification methods include chemical grafting and copolymerizing, physical blending, as well as nanocomposites. − Among them, chemical copolymerizing, i.e., in-reactor alloy technology, seems to be a promising strategy, where propylene is copolymerized with other olefin monomers (e.g., ethylene, butylene, etc.) in the homopolypropylene porous powders. , As a result, a PP-based multiphase system is achieved in the reactors, including homopolypropylene as the continuous phase and PP-based intrinsic elastomer as the dispersion phase. − Particularly, owing to the continuous in situ copolymerization, the dispersed phase size of in-reactor alloy (in the scale of less than a micron dimension) is much smaller and more uniform than that of traditional blends, thus improving comprehensive performance effectively. , Furthermore, in-reactor alloy technology makes it possible to produce a multiphase polymer with sequential polymerization .…”