Boron Nitride/Cellulose Nanofiber‐Modified Waterborne Epoxy Sizing Agent for Enhancing the Mechanical Properties and Thermal Conductivity of Carbon Fiber Composites

ABSTRACT Suboptimal interfacial adhesion between carbon fibers (CFs) and resin matrix has been an important factor limiting the application of composites. Hence, this work synthesized a functionalized boron nitride/cellulose nanofiber multi‐component nano‐hybrid modified waterborne epoxy sizing agent, which was coated on the CF surface to improve the interfacial performance of the composites. The results showed that the flexural strength, flexural modulus, interlaminar shear strength (ILSS), and interfacial shear strength (IFSS) of the prepared CF composites increased by 44.72%, 43.46%, 57.03%, and 60.39%, respectively. These advancements stem from the synergistic interaction between CNFs and BN, which enhances the chemical reactivity and surface roughness of the fiber surface and promotes the chemical bonding and mechanical interlocking between the fiber and the resin. In addition, the thermal conductivity of the composites was significantly improved by 48.7%, which was attributed to the establishment of a continuous thermal conductivity pathway within the composites between BN and CNFs. The high‐strength, high‐thermal‐conductivity composite material developed in this research offers broad application prospects across multiple fields.