Novel Sandwich-Structured Flexible ANF/PMIA/ANF Composite Paper with Enhanced Breakdown Strength

With the rapid development of cutting-edge electrical equipment and electrical systems, it is of great significance to develop advanced polymeric insulating paper with high breakdown strength under a high-temperature environment. In this paper, aramid nanofibers (ANF) and original poly(m-phenylene isophthalamide) (PMIA) paper were utilized to construct ANF/PMIA/ANF composite papers with sandwich structure. On account of the reduced surface roughness of the original PMIA paper, the high breakdown strength of ANF layers and formed high-density electron traps, the breakdown strength of ANF/PMIA/ANF composite paper is significantly enhanced. The Weibull breakdown strength ANF/PMIA/ANF composite paper with 4 mg/mL of ANF are 82.7 MV/m at 25 °C and 61.7 MV/m at 100 °C, which are 165.1 and 137.4% of the A-P-A-0 at 25 and 100 °C, respectively. Additionally, the flame-retardant property of ANF/PMIA/ANF composite paper is also obviously improved with increasing concentration of ANF. Consequently, this work offers an opportunity for the development of novel polymeric insulating paper with enhanced breakdown strength in a wide temperature range.