Improving the Insulation Performance of Polyimide/Al2O3 Composite Films Through Surface Modification

With the continuous advancement of electronic devices toward miniaturization and high-power operation, there is an increasing demand for polymer dielectric materials exhibiting enhanced electrical insulation and thermal management capabilities. This study develops a high-performance polyimide (PI)/Al2O3 composite film through targeted surface modification of the inorganic filler. The surface of nano-Al2O3 was modified to enhance the interfacial compatibility between the inorganic filler and the polymer matrix, thereby reducing filler agglomeration. The comparative analysis reveals that unmodified Al2O3 gradually reduces dielectric strength with increasing content due to interfacial defects and particle aggregation, whereas the modified composites exhibit distinct characteristics. The addition of just 1 wt% Al2O3@KH550 significantly enhances electrical insulation performance, achieving an optimal breakdown strength of 547.7 kV/mm—surpassing both pure polyimide and unmodified composites at equivalent loading. This performance peak is attributed to improved interfacial bonding, which mitigates electric field concentration at the filler-matrix interface. The results demonstrate that silane coupling agent modification effectively optimizes interfacial compatibility, enabling the preparation of polyimide composite films with exceptional dielectric properties for advanced electronic applications.