Sustainable Bio‐Based Thermally Conductive Epoxy Composites With Recyclable Three‐Dimensional Boron Nitride Networks

ABSTRACT Developing sustainable polymer composites with high thermal conductivity at low filler loadings is essential for advanced thermal management. Herein, a bio‐based thermally conductive composite was fabricated by vacuum impregnating a preconstructed three‐dimensional boron nitride (3D BN) scaffold with epoxidized soybean oil/citric acid/tetraethyl orthosilicate (ESO/CA/TEOS) resin. The optimized ESOCA7 matrix, with a carboxyl‐to‐epoxy molar ratio of 0.7, exhibited a high gel fraction, low water uptake, improved mechanical properties, and alkali degradability. The interconnected 3D BN scaffold, constructed by salt templating with waterborne polyurethane as a binder, provided continuous thermal conduction pathways and reduced interfacial thermal resistance. Consequently, the 3D BN‐10/ESOCA7 composite containing only 10 vol% BN achieved a thermal conductivity of 1.063 W/(m·K), representing a 423.65% improvement relative to neat ESOCA7. Infrared thermography and finite element simulations further verified the superior heat transfer performance of the 3D interconnected network. Moreover, degradation of the bio‐based matrix enabled the recovery and reuse of the 3D BN scaffold, and the regenerated composites maintained satisfactory thermal conductivity after three reuse cycles. This work provides a sustainable route to fabricate recyclable bio‐based polymer composites that deliver efficient thermal transport under low filler loadings.