High Performance Cellulose Insulation Paper Enabled by Dual-Phase nano-ZnO/PI Strategy

Cellulose-based insulation paper is widely used in high-voltage equipment, but its limited thermal conductivity and dielectric strength restrict reliable performance under elevated temperatures and strong electric fields. In this work, a dual-phase composite paper is developed by incorporating nano-ZnO and polyimide (PI) into a cellulose matrix, guided by molecular dynamics (MD) simulations. The combined fillers improve interfacial compatibility, suppress void defects, and establish continuous thermal pathways together with stable insulating barriers. Simulation predictions of enhanced thermal transport, charge suppression, and mechanical reinforcement are verified by experiments. The optimized formulation containing 3 wt% nano-ZnO and 6 wt% PI achieves a thermal conductivity of 0.294 W·m⁻¹·K⁻¹, a tensile strength of 72.12 MPa, corresponding to 87.26% and 41.02% improvements over pure cellulose (P0). Meanwhile, the breakdown strength increases from 60.22 to 73.51 kV·mm⁻¹ (+22.07%), and the relative permittivity and dielectric loss tangent decrease to 2.49 (−40.86%) and 0.46% (−43.21%). These results demonstrate that the dual-filler strategy provides a structurally compact and functionally stable composite architecture, enabling simultaneous enhancement of thermal, mechanical, and dielectric properties. This study confirms the effectiveness of simulation-guided design in accelerating the development of multifunctional cellulose-based insulating materials and highlights their potential for application in next-generation high-voltage power systems.