Synergistic enhancement of dielectric strength and thermal conductivity in meta-aramid-based composite films via honeycomb cavities filling strategy

Owning superior dielectric and mechanical properties, poly (m-phenylene isophthalamide) (PMIA) fiber is an ideal insulation material for next-generation electric and electronic devices. However, its low thermal conductivity poses a risk of thermal breakdown. Moreover, PMIA films prepared using the unique protonation method exhibit a honeycomb-like structure with numerous air pockets, further reducing heat transfer efficiency. Herein, we propose a strategy of honeycomb cavities filling to synergistically improving the dielectric strength and thermal conductivity of PMIA-based composite films. To achieve a denser configuration, the nanodiamond (ND) fillers modified by polydopamine (PDA) are uniformly filled in the cavities within the PMIA skeleton, serving as thermally conductive reinforcements. In the 15 wt% composite film, the breakdown strength and thermal conductivity measure 334 kV/mm and 1.12 W/(m·K), respectively, which are 42.3 % and 833 % higher than that of the pure one. Furthermore, the underlying mechanisms are studied based on density functional theory and multi-physics simulations.