LAUSR

Polypropylene (PP) has attracted significant attention as a recyclable thermoplastic for high‐voltage direct current (HVDC) cable insulation, potentially replacing conventional cross‐linked polyethylene (XLPE). This study systematically investigates the effects of cooling rate (10, 20, and 30°C/min) during melt processing on the crystalline structure and electrical properties of PP insulation material. Through comprehensive characterization using polarized optical microscopy, X‐ray diffraction, and differential scanning calorimetry, the results indicate that increased cooling rates effectively suppress spherulite formation, reducing average spherulite diameter and decreasing crystallinity from 52% to 44%. These structural modifications yield a 450% enhancement in volume resistivity from 4.11 × 1013 to 2.26 × 101⁴ Ω m, along with a 21.4% improvement in DC breakdown strength from 224 to 272 kV/mm when measured at 70°C. However, space charge measurements reveal the presence of space charge accumulation at elevated temperatures, which we attribute to lattice defects induced by rapid crystallization. The results establish a quantitative processing‐structure‐property relationship, showing that controlled cooling rate optimization can significantly enhance PP's electrical performance for HVDC applications while maintaining its recyclability advantage over XLPE.