Flexible and robust TEMPO-oxidized cellulose nanofibrils/mica composite as paper dielectrics with enhanced dielectric property

Environmental-friendly and high-performance biopolymer-based dielectrics have attracted great attention in light weight and flexible electronics. In this work, the biodegradable TEMPO-oxidized cellulose nanofibrils (TOCNs) were mixed with inorganic mica platelets through vacuum-assisted filtration and subsequent hot-pressing method. It was found that mica platelets could be well aligned within TOCN matrix to form a nacre-like multilayer structure due to good compatibility and hydrogen bonding interaction between mica and TOCNs. The TOCN/mica composite paper shows good flexibility, high mechanical strength (9.8 MPa) and enhanced dielectric breakdown strength (17.85 kV/mm). TOCN/mica papers were further dip-treated by epoxidized soybean oil (ESO) and cured at 170 °C for 2 h. The ESO-treated composite papers show greatly enhanced breakdown strength and reach as high as 175.65 kV/mm for TN-M50/ESO sample. Therefore, these cellulose nanofibrils-based composite papers have shown great potentials in paper insulator in power transformers.