Low-Filler, High-Thermal-Conductivity Aramid Insulating Paper: Constructing Effective Thermal Conduction Networks via Boron Nitride/Aramid Composite Fibers

To address the critical thermal management challenges in highly integrated electronics, this work reports an aramid insulating paper based on a thermally conductive fiber skeleton that constructs an efficient heat-transfer network. Hydroxylated boron nitride nanosheets (BNNs–OH) were encapsulated within a meta-aramid (PMIA) matrix via wet-spinning, producing PMIA/BNNs–OH composite fibers (PBf) with considerable mechanical strength and high axial thermal conductivity. Subsequently, PBf, serving as the skeleton, were integrated with commercial fibrillated fibers (Pf) through the wet-web forming process to fabricate PMIA/BNNs–OH composite paper (PBp). The well-ordered thermal network established by PBf enables PBp to achieve a remarkable through-plane thermal conductivity of 0.833 W·m–1·K–1 at a low BNNS–OH loading of 5 wt % total mass, representing a 678% enhancement over the pristine PMIA paper. Additionally, PBp maintains excellent thermal stability with negligible mass loss at 400 °C and superior electrical insulation (volume resistivity >1015 Ω cm, representing a 355% enhancement over pure PMIA paper). Its exceptional heat dissipation capability was validated in LED modules, reducing surface temperatures by 22.7% compared to conventional aramid paper. This combination of properties substantiates the significant promise of PBp for thermal management in high-power electronics.