Enhancing the Comprehensive Properties of Polypropylene Films via Organic–Inorganic Interfacial Molecular Engineering

ABSTRACT As an important insulating medium for high‐voltage direct‐current transmission capacitors, polypropylene (PP) film requires the synergistic optimization of its insulating properties, dielectric properties, and thermal stability to enhance the reliability of capacitor equipment. While doping the PP matrix with nanoparticles can effectively increase the material's relative permittivity, issues such as agglomeration and interfacial incompatibility lead to reduced dielectric strength and thermal stability. Based on this, this paper proposes an organic–inorganic interface molecular engineering strategy to improve the interfacial compatibility between nanoparticles and PP, and to construct deep‐level charge traps to suppress leakage current, thereby achieving a synergistic enhancement of the material's relative permittivity, dielectric strength, and thermal stability. PP/INA‐Al 2 O 3 composite films with different doping concentrations were prepared by surface‐treating nano‐Al 2 O 3 with isonicotinic acid (INA). Experimental results indicate that INA‐Al 2 O 3 doping effectively enhances the film's crystallinity. The PP/INA‐Al 2 O 3 film with 1.0 wt% doping achieved a breakdown strength of 562.44 kV/mm at room temperature, representing an approximately 35% increase compared to pure PP. At 85°C, the breakdown strength reached 528.17 kV/mm, demonstrating excellent insulation stability and thermal stability. Furthermore, the relative permittivity of PP/INA‐ Al 2 O 3 was also significantly higher than that of pure PP.