Synergistic effect of BNNS and MgAl layered double hydroxide nanosheets on dielectric properties and thermal conductivity of polyetherimide nanocomposite films

Abstract The development of polymer‐based dielectric nanocomposites with superior dielectric properties, heat dissipation, and excellent thermal stability remains a significant challenge for advanced electronic and electrical systems. In this work, boron nitride nanosheets (BNNS) and MgAl layered double hydroxide nanosheets (MgAl LDHNS) were utilized as binary fillers and incorporated into polyetherimide (PEI) to fabricate BNNS‐MgAl LDHNS/PEI nanocomposite films by ball milling dispersion and solution casting method. Owing to the exceptional synergistic effect of BNNS with high thermal conductivity and large diameter, combined with MgAl LDHNS with high dielectric constant and small diameter, the dielectric constant and thermal conductivity of the nanocomposite film were enhanced while maintaining low dielectric loss and high breakdown strength. For the BNNS‐MgAl LDHNS/PEI nanocomposite films with filler loading of 12 wt%, the dielectric constant (6.47 at 100 Hz) increased by 73%, the in‐plane thermal conductivity (6.932 W/m·K) and through‐plane thermal conductivity (0.407 W/m·K) increased by 561% and 111%, respectively. And the breakdown strength of the nanocomposite film remains at 82.1 kV/mm. Simultaneously, the thermal stability and mechanical flexibility of the nanocomposite film were maintained. This work presents a promising PEI‐based composite material and offers new insights into the role of two‐dimensional binary fillers with varying sheet diameters in enhancing the properties of polymer‐based composites. Highlights BNNS‐MgAl LDHNS/PEI nanocomposite film was prepared. The nanocomposite film has high dielectric and thermal properties. The interfacial polarization synergistic enhanced by the 2D binary fillers. A high thermal conductivity path was formed between 2D binary fillers.