Dielectric Properties and Insulation Performance of Nanocellulose Composite Films Enhanced by Hyperbranched Boron Nitride

ABSTRACT Boron nitride (BN), characterised by its wide band gap and robust dielectric properties, has emerged as a promising filler for polymer‐based dielectric composites. Nevertheless, its practical implementation in polymer matrices has been hindered by poor dispersibility and inadequate interfacial adhesion. This study addresses these challenges by developing hyperbranched polymer (HBP)‐functionalised BN (HBP‐BN) and fabricating HBP‐BN/cellulose nanofiber (CNF) composite films via vacuum‐assisted self‐assembly. The HBP‐BN/CNF films demonstrate a low dielectric loss (tan δ < 0.016) and significantly improved volume resistivity (10 9 Ω·m) and high thermal stability (55.36% residual mass at 800°C). Notably, the surface flashover voltage is elevated from 13.82 to 15.61 kV, demonstrating superior insulation capability. All these results highlight the promising potential of HBP‐BN/CNF composite films for use as advanced dielectric materials, providing a novel approach to develop eco‐friendly high‐performance materials for high‐voltage insulation systems in next‐generation electronics and electrical devices.