Mechanically robust and uniform aramid nanofiber films fabricated using repeated spin-coating and protonation processes

Aramid nanofiber (ANF) films show promise for various industrial applications, but their applicability has been constrained by the low mechanical properties, which are mainly due to their incomplete packing and non-uniform microstructure. This work introduces an efficient method for significantly improving the mechanical properties of ANF films using repeated spin coating and protonation. The method allows for the preparation of ANF films with highly uniform microstructures and adjustable thicknesses while achieving excellent mechanical properties. These ANF films have a Young's modulus of 6.8 GPa, tensile strength of 310 MPa and hardness of 248 MPa, surpassing those produced using previous methods. A comprehensive analysis of the surface and cross-sectional morphologies, chemical composition, thermal stability, and mechanical properties was also carried out to characterize the film properties.