Molecular and Microstructural Engineering Strategies for High-Performance Polypropylene Insulation Materials

This study develops a high-performance polypropylene (PP) substrate platform by optimizing micro/macrostructures and introduces an efficient catalyst. Key findings include: (1) microstructural analysis identifies ash content impurities (>20 ppm) as triggers for partial discharge-induced insulation failure. PP molecular weights (105–106) with narrower distributions enhance mechanical strength, while functional groups (-CH2/-CH3) show no structural variations across samples. (2) Macroscopically, mixed α-β crystal interfaces increase insulation failure risks, necessitating single-crystalline structures. Higher temperatures reduce dielectric constants but increase losses, requiring environmental consideration. Crystallinity positively correlates with DC breakdown strength (443.31 kV/mm at 54.13% crystallinity). (3) Among three endo-donor catalysts, the internal electron donor 3-based catalyst achieved optimal die-test activity (47.7 kg PP/g cat·h). With 20 mL triethylamine, the catalyst reduced PP ash content by 42.1%, narrowed molecular weight distribution by 31.6%, and increased crystallinity by 8.74%. These results establish microstructure–property relationships for PP capacitors and provide technical guidelines for performance enhancement. The work addresses current limitations in PP evaluation methods and offers a practical strategy for manufacturing high-insulation PP materials through structural control and catalytic optimization.