Dynamic Covalent Network Mediated Recyclable High-Voltage Direct Current Cable Insulation with Superior Mechanical and DC Electrical Properties

Abstract Polypropylene (PP) is an important candidate for next generation environmentally friendly high-voltage direct current (HVDC) cable insulation materials. However, its insufficient toughness often require modification through blending with polyolefins such as polyethylene (PE). The poor compatibility between PP and PE tends to form unstable phase interfaces, thereby weakening the mechanical, thermomechanical, and dielectric properties. To address the poor compatibility and the deterioration of high-temperature electrical properties in multiphase PP insulation materials, this study proposes an interfacial modification strategy based on dynamic covalent bonds, in situ constructing a dynamic cross-linking network within maleic anhydride-grafted PP and PE blends. Microstructural characterizations reveal that this network overcomes the compatibility barrier of the multiphase system, achieving highly stable interfaces and optimized crystal structures. Direct current electrical tests indicate that, under the confinement and regulation of the dynamic network, the high-temperature electrical properties of the material are significantly enhanced. Notably, at 70 °C, the injection and accumulation of space charge are effectively suppressed, and an extremely low conduction current is maintained. This research not only achieves the synergistic enhancement of the mechanical, thermomechanical, and electrical properties of multiphase polyolefins, but also provides crucial theoretical and practical support for the development of high-performance, recyclable insulation materials that meet the demands of next-generation HVDC transmission.