Dynamic Covalent Chemistry Enables Self-Healing and Compatibilization in Polypropylene Composites

Abstract

Polypropylene is a promising eco-friendly cable insulation material owing to its impressive electrical properties, yet its inherently inferior mechanical performance limits direct application. Blending with elastomers is commonly employed to address mechanical deficiencies in polypropylene, but it induces phase incompatibility and space charge accumulation, compromising insulation performance. Moreover, the interfaces are prone to damage under high mechanical or electrical stress, and such damage is often irreversible, hindering the long-term stability of the composites. Herein, a nitrogen-boron crosslinked polypropylene/polyolefin elastomer (NBPP) composite is developed through post-modification and dynamic covalent chemistry. The dynamic bonds at the interface link immiscible phases and localized charge migration, while trap-rich regions in the bulk phase suppress carrier mobility. This interface-guided, bulk-trapped structure effectively enhances phase compatibility and reduces space charge accumulation. The optimized sample achieves a breakdown strength of 572 kV mm⁻¹ and minimal electric field distortion (~8.6% at 70 °C under 50 kV mm⁻¹). The reversible nature of the borate ester bonds enables self-healing under thermal activation, allowing recovery from multiple types of damage and repeated thermal reprocessing. This approach provides an innovative strategy for high-performance, sustainable, and self-healing polymeric insulation materials for next-generation high-voltage direct current transmission systems.

Keywords

compatibility / dynamic covalent chemistry / high-voltage direct current cables / polypropylene composites / self-healing

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