Hierarchical Sandwich-Structured Polyarylate Nanofiber/Meta-Aramid Nanocomposite With Robust Dielectric Strength, Mechanical Durability, and Environmental Stability

Meta-aramid (PMIA) insulating paper contains micron-scale pore defects that limit its dielectric strength and reliability under high electric field and power conditions. Inspired by a sandwich structure, this study employed self-fabricated polyarylate (PAR) nanofiber membranes as outer layers and commercial aramid paper as the core to fabricate hierarchical PAR/PMIA/PAR nanocomposite insulating paper via a scalable hot-pressing consolidation process. The high-aspect-ratio PAR nanofibers formed a dense interwoven network, reducing pore density and mitigating electrical weak points. During hot pressing, the reversible melting of PAR effectively sealed inter-fiber and interfacial pores, while π–π conjugation and strong hydrogen bonding with PMIA fibers ensured robust interfacial adhesion, suppressing electric field distortion from charge accumulation. As a result, the nanocomposite achieved tensile and breakdown strengths of 97.406 MPa and 114.55 kV/mm, representing increases of 51.3% and 204.3% over commercial aramid paper. After thermal aging at 200°C and 24 h UV exposure, breakdown strengths remained at 62.89 and 71.57 kV/mm (vs. 24.62 and 27.30 kV/mm for commercial aramid paper). Even after 20 crumpling-twisting cycles and 100 folding cycles, breakdown strengths exceeded 46.78 kV/mm, demonstrating outstanding durability and structural stability under extreme thermal, mechanical, and radiation conditions. Compatible with industrial wet-laid papermaking and hot-pressing, this work provides a realistic route toward scalable manufacturing of lightweight insulating papers for high-power motors, transformers, and photovoltaic modules requiring long-term dielectric reliability. Highlight Sandwich-structured nanocomposite with robust π–π conjugation interface. 114.55 kV/mm dielectric strength, 204.3% higher than commercial aramid paper. Tensile strength of 97.4 MPa, 51.3% higher than commercial paper.