Thermoplastic Polyurethane Composites With Enhanced Thermal Conductivity and Favorable Mechanical Properties via 3D Printing‐Induced Oriented‐Boron Nitride/Alumina Network

ABSTRACT Controllable filler distribution to construct thermal conductive pathways is critical for optimizing polymer composite thermal conductivity. Herein, FDM 3D printing was utilized to precisely regulate the orientation of boron nitride (BN) microplatelets in thermoplastic polyurethane (TPU), and spherical alumina (Al ₂ O ₃ ) was co‐filled as a thermal conductive bridge between oriented BN to construct a thermal conductive network under the action of structural complementarity. Meanwhile, we systematically revealed the synergistic effect of hybrid fillers with different proportions and contents, and further explored the regulation mechanism of printing process parameters on the thermal conductive network and properties of composites. It was found that the shear and compression effects during the extrusion and deposition of composite melt could induce the oriented arrangement of BN along the printing plane, and an appropriate proportion of Al ₂ O ₃ could not only enhance the orientation of BN but also act as an effective bridge to connect BN. In addition, a smaller nozzle diameter and layer height were proven to provide a greater effect on the melt shear flow, which is conducive to the formation of a highly oriented filler network. Therefore, the thermal conductivity of BN/Al ₂ O ₃ /TPU with the highly oriented BN/Al ₂ O ₃ network reaches 2.73 W/m K, which is 1.16 times that of BN/TPU and 13.65 times that of pure TPU, accompanied by excellent thermomechanical properties, and holds great significance in the electronic device thermal management.