Synergistic enhancements of mechanical and insulating properties in electrospun PMIA-based composite films

With the continuous pursuit of high voltage levels and integration in electrical devices, greater demands are placed on the operational performance of poly (m-phenylene isophthalamide) (PMIA)-based materials. Owing to the interfacial defects during preparation and modification, the enhancement of breakdown strength (Eb) and mechanical properties is always challenging. Herein, a novel PMIA film is prepared using electrospinning coupled with the hot-pressing method. High-speed spinning enables the directional arrangement of nanofibers, while the subsequent hot-pressing facilitates the physical crosslinking and consolidates the entire structure. Nanodiamond (ND) coated with polydopamine (PDA) is additionally incorporated as the reinforcement. As the loading ratio reaches 3 wt%, a synergistic enhancement of Eb and Young’s modulus (Y) is achieved, with the values of 5.92 GPa and 526.90 MV m−1 at room temperature, respectively, outperforming many previously reported works. Notably, even at 150 °C, the Eb and Y still remain at 4.98 GPa and 481.70 MV m−1, respectively. The introduction of ND@PDA fillers contributes to optimizing the thermal stability, mechanical properties, and effectively reducing the leakage current by inhibiting charge transport. The underlying mechanism is revealed by molecular dynamics and density function theory analysis, offering guidelines for the preparation of advanced PMIA-based composites in the future.