3D printing of boron nitride polymer composites for tailored thermal transport and mechanical performance

Abstract

Hexagonal boron nitride (h-BN) microplatelets are layered structural materials known for their thermal stability, chemical resistance, electrical insulation, and anisotropic thermal transport behaviors. They are highly thermally conductive in-plane yet possess relatively low through-plane conductivity and as a result their orientation plays a critical role in the overall thermal transport performance of h-BN/polymer composites. In this study, masked stereolithography (MSLA) 3D printing approach was used to investigate how h-BN platelet size, filler loading, and printing layer thickness affect platelet alignment, heat transfer, and mechanical behavior. Three types of h-BN microplatelets with average lateral sizes of 0.9, 12, and 45 μm were incorporated into a UV curable resin at loadings up to 20 wt% and printed with layer thicknesses of 10–50 μm. The characterization results from X-ray diffraction, optical microscopy, and scanning electron microscopy showed that larger h-BN platelets aligned more effectively along the printing plane, especially when thinner layers were used. This alignment improved in-plane thermal transport, with the highest thermal conductivity obtained for the BN45 composite printed at a 10 μm layer thickness. Mechanical testing showed that BN addition generally increased the elastic modulus, while tensile strength showed a more composition-dependent trend. Overall, these results show that MSLA 3D printing can tune h-BN platelet orientation through filler size and layer thickness, providing a practical route to effectively tailor the thermal and mechanical behavior of BN/polymer composites.