Thermally conductive prepreg GFRP composites with boron nitride networks using a facile salt template method

• Segregated 3D-BN structure applied to GFRPs for enhanced thermal conductivity. • 3D-BN fabricated via a green, cost-effective NaCl templating method combined with EVA. • 3D-BN/epoxy composites demonstrated 485–792% higher thermal conductivity than pure epoxy. • Thermal conductivity improved by 489% compared to pure epoxy prepreg GFRPs. With the miniaturization and performance enhancement of electronic devices, the effective thermal management of circuits has become increasingly critical. In addition, the demand for glass-fiber-reinforced polymers (GFRPs) with enhanced thermal conductivity, particularly pre-impregnated (prepreg) GFRPs, for use in printed circuit board has gained significant attention. In this regard, polymer composites incorporating boron nitride (BN) as an inorganic filler have been explored to overcome the intrinsically low thermal conductivity of polymers. Recent research advancements have introduced methods to develop low filler content composites that maintain the excellent mechanical properties of epoxies without significant degradation. In this study, a facile NaCl-template process was applied to form thermally conductive pathways at low filler content. Three-dimensional (3D)-BN/epoxy composites exhibited superior thermal conductivity to randomly dispersed BN/epoxy composites, achieving 2.06 W/(m·K) at 20 vol% filler contents. Furthermore, when the NaCl-template method was applied to prepreg GFRP, the composites showed higher thermal conductivity than pure epoxy GFRP. As a result, a novel prepreg was developed via the NaCl-template process, providing heat dissipation while maintaining mechanical robustness and electrical insulation. Extending the NaCl-template method to prepreg GFRP offers an eco-friendly route to lightweight thermal management materials that combine high thermal conductivity with reliable mechanical strength and insulation.