Superhydrophobic meta-aramid papers prepared by the surface-embedded spray coating strategy

Meta-aramid fiber (poly(m-phenylene isophthalamide), PMIA) with superior mechanical strength, thermal stability, and insulation properties is a promising fiber material. However, the hydrophilic nature extremely limits its further development in practical applications. Herein, we report on the preparation of the superhydrophobic PMIA papers based on a novel spray coating strategy, by which the coating material is surface-embedded on the PMIA. Owning the unique deprotonation and regeneration characteristics, the PMIA paper is reconstructed with a denser configuration and hierarchical micro-nano surface, supplying amounts of attaching sites for the coating materials of silyl group-modified nano-SiO2. Assisted by the mechanical interlock and electrostatic interaction at the interfaces, a homogeneous and continuous coating layer is formed on the premise of preserving the intrinsic properties of the PMIA substrate. The as-prepared PMIA paper exhibits superior superhydrophobicity with a maximum contact angle beyond 153° and a minimum sliding angle smaller than 2°. This characteristic is extremely favorable for suppressing the surface discharge under various complex operating conditions. Compared with the pristine PMIA paper, the wet and pollution flashover voltages are increased by 194% and 266%, respectively. Furthermore, the correlation between the dynamic behaviors of a water droplet and the improved wet flashover strength is discussed.