Dual‐Effect Integration of Thermal Management and Flame Retardancy for 3D Boron Nitride/Epoxy/Benzoxazine Composites

ABSTRACT The rapid progress of interdisciplinary fields, such as advanced materials and electronic devices, presents high challenges for multifunctional composites that integrate thermal management and flame retardancy. This study proposed a 3D honeycomb structure composed of boron nitride thermal conductive skeleton and benzoxazine flame retardant, constructing epoxy composites that dual‐functional integrate thermal conductivity and flame retardancy. The through‐plane thermal conductivity of the 3D composite reaches 2.64 W m −1 K −1 , representing a 1167% improvement compared to epoxy resin. The thermal impedance is reduced from 66.37 to 4.16 K cm 2 W −1 , demonstrating rapid heat conduction and dissipation capabilities. Furthermore, a novel 3D spatial barrier effect is discovered via optimising the flame retardant performance of the epoxy composite. This 3D composite exhibits a limiting oxygen index (LOI) value of 41.3% and achieves a vertical burning (UL‐94) V‐0 rating. The peak heat release rate, total heat release, peak smoke production rate, and total smoke production decreased by 58.2%, 40.7%, 45.7%, and 26.1%, respectively. This work also demonstrated the thermal management application of the 3D composite in LED chip heat dissipation and its potential flame retardant application in polymer lithium‐ion battery packaging, providing valuable insights for designing polymer composites with dual‐effect integration.