All-Organic Aramid Films with High Temperature Resistance and Electrical Insulation by Introducing Interfacial Hydrogen Bonds

Although aramid nanofibers (ANFs) consist of rigid poly(terephthalic acid terephthalamide) molecular chains with good high temperature resistance for aerospace and other high-temperature applications, it has poor electrical insulation properties due to internal defects. Currently, the main method to improve the electrical insulation properties is to introduce wide band gap two-dimensional (2D) fillers, such as Boron Nitride Nanosheets (BNNS) or mica flakes, but this inevitably affects the mechanical properties and optical transparency. Cellulose acetate (CA) is originated from acetylation of natural cellulose, and the higher number of hydrogen bond donors on the molecular chain enables it to interbond with many polymers. In this study, CA was introduced into ANFs films, and the all-organic aramid films were prepared by blade coating method. A high dielectric constant of 14.4 as well as a low dielectric loss (0.062 @103 Hz) were obtained, and the dielectric loss of all films was lower than that of the ANFs films, which is attributed to the introduction of interfacial hydrogen bonds that suppressed the loss. In addition, the introduction of interfacial hydrogen bonds introduced deep traps inside the all-organic aramid films, which further improved in breakdown strength from 216.11 MV/m for ANFs film to 367.8 MV/m for the 5 CA film. The prepared all-organic aramid films also showed excellent flexibility as well as high temperature resistance, and the electrical insulation performance under different extreme environments was still higher than that of the ANFs films. This study provides a method for the preparation of high temperature resistant and electrically insulating films, which have great potential applications in fields relating to high temperature circumstance.