Comparative study on the mechanical and dielectric properties of aramid fibrid, mica and nanofibrillated cellulose based binary composites

High-performance insulation materials are widely used in transformers, electric generators and insulated wires of the high-speed trains and airplanes. However, the relatively poor mechanical and dielectric properties of the traditional insulation materials severely limit their application fields, especially in the harsh conditions. In this study, we prepared three binary composite films, including aramid fibrid/mica (AM), aramid fibrid/nanofibrillated cellulose (AN) and mica/nanofibrillated cellulose (MN), through a vacuum-assisted filtration and thoroughly investigated their mechanical and dielectric properties. Due to the dense nacre-like lamellar structure and strong interfacial bonding strength between mica and nanofibrillated cellulose (NFC), the MN composites exhibit the highest tensile strength of 34.6 MPa and excellent dielectric breakdown intensity of 17.1 kV/mm. The AM composite film has good thermal stability owing to the inherent high temperature resistance of aramid fibrid and mica, but shows the lowest tensile strength and dielectric breakdown intensity. The AN composite film shows the compromise mechanical and dielectric properties.