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

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.