High‐performance composite paper based on heterogeneous polyimide fibers with enhanced mechanical and dielectric properties

Abstract With the advancement and modernization of industrial technology, the demands placed on the comprehensive properties of high‐performance insulating paper by various industries have become increasingly stringent. Polyimide (PI) fiber‐based paper with exceptional heat resistance and electrical insulation capabilities can fulfill the requirements of high‐temperature‐resistant insulating materials in advanced industrial technology. However, the challenges in pulping and dispersing PI fibers have constrained the production of all PI‐based papers. In this study, feathered polyamide acid (PAA) fibrids with yarn‐splitting morphologies were firstly prepared through precipitation strategy under “high‐speed rotation‐shear” process, which were then wet‐formed with PI chopped fibers through papermaking process following with chemical imidization and hot‐pressing posttreatment. With the optimized components of PAA papers and imidization process, the mechanical properties of PI‐based paper could improve to 14 MPa, with a breakdown strength of 40 kV/mm. Furthermore, the obtained all‐PI composite paper demonstrated excellent resistance to aging with dielectric properties remaining relatively stable after a specified aging period, exhibits outstanding overall performance and broad application prospects in the field of electrical insulation. Highlights Feathered polyamide fibrids were prepared via high‐speed shear precipitation. The components and imidization process of composite papers were optimized. The paper showed tensile strength of 14 MPa and breakdown strength of 40 kV/mm. The paper demonstrated excellent resistance to oil aging with good properties.