Micro/Nanofiber-Network Assembled Aramid Paper with Excellent Mechanical and Electrical Insulating Properties.

Aramid nanofiber (ANF) paper exhibits excellent dielectric strength, positioning it as a promising candidate for an electrical insulating material. However, it suffers from extremely poor tear strength induced by the tremendous hydrogen bond and fully immobilized nodes among the ANF network that significantly restrict their capacity for energy dissipation through fiber slippage and network redistribution, causing rapid crack propagation and catastrophic tearing for ANF paper. Herein, we report a PMIA@ANF composite nanopaper with a reinforced-concrete architecture assembled by the microscope poly(m-phenylene isophthalamide) (PMIA) fiber and ANF network with optimized nodal strength and density, facilitating timely dissipation of shear stresses through fiber slippage and network redistribution, thereby retarding catastrophic tearing. The obtained PMIA@ANF composite nanopaper achieves a mechanical breakthrough with a tear strength of 1899 mN, representing a 47.5-fold enhancement over ANF paper. Surprisingly, the micro/nano synergy of PMIA@ANF network eliminates voids within the traditional PMIA network, achieving a gratifying dielectric strength of up to 82.8 kV·mm-1. The PMIA@ANF composite nanopaper significantly outperforms previously reported electrical insulation composites in both tear strength and dielectric strength, attributable to its exceptional reinforced-concrete architecture that synergistically balances structural durability and dielectric reliability. Furthermore, the PMIA@ANF composite demonstrates exceptional environmental resilience, as evidenced by its retained performance under extreme conditions spanning high temperatures (100-200 °C), cryogenic exposure (-196 °C), and corrosive chemical environments. These attributes position PMIA@ANF composite nanopaper as a promising candidate for advanced electrical insulation in next-generation insulation equipment.