Study on the Aggregation Structure and Space Charge Accumulation Characteristics of Polypropylene Insulation for HVDC Cables

Developing eco-friendly high-voltage direct current (HVDC) cables requires insulation materials combining recyclability with superior dielectric properties. This study addresses the critical challenge of balancing mechanical toughness and electrical performance in non-crosslinked polypropylene (PP) by inducing$\beta$-crystal formation via$\beta$nucleating agents in POE-toughened PP systems. Through systematic variation of$\boldsymbol{\beta}$-nucleator concentrations ($\mathbf{0}, \mathbf{0. 0 5}, \mathbf{0. 1}$, 0.3, and$0.5 \text{wt} {\%}$), we correlate structural evolution with space charge dynamics under$30 \text{kV} / \text{mm}$DC fields. At the optimal 0.1 wt% loading, X-ray diffraction reveals exceptional$\beta$-crystal content (95.10%) and peak crystallinity, while scanning electron microscopy confirms refined POE dispersion (average domain size reduced by 36.8% vs. control) and stabilized interfaces. These structural advantages collectively suppress interfacial charge trapping, yielding a 57.6% reduction in space charge accumulation and minimal electric field distortion ($\delta=3.73 {\%}$). Mechanistic analysis demonstrates that$\beta$-crystals enhances matrix crystallinity and strengthens PP-POE molecular chain interactions, thereby stabilizing phase interfaces and aggregation morphology. This work establishes$\beta$-nucleation as a additive solution for simultaneously upgrading mechanical and electrical properties, advancing sustainable HVDC cable design.