Improved thermal conductivity of thermoplastic polyurethane via aligned boron nitride platelets assisted by 3D printing

Thermal management is of importance to microelectronics. Owning both excellent thermal conduction and electrical insulation, hexagonal boron nitride (hBN) platelets are widely used in polymer matrices. While the thermal properties rely on the orientation of hBN platelets in polymer matrices significantly. Herein, we report that high thermal conductive hBN filled thermoplastic polyurethane (TPU) composites can be achieved by a fused deposition modeling 3D printing technique. The hBN platelets show excellent alignment along printing direction in TPU matrix due to the shear-inducing effect of printing. The sample along printing direction at filler loading of 25.9 vol% (40 wt%) exhibits the thermal conductivity up to 2.56 Wm(-1) K-1 at 100 degrees C along printing direction, i.e. 10- and 2.8-time enhancement, compared to those of neat TPU and hBN/TPU sample tested along thickness direction. The surface temperature distribution of samples with various heating durations is also presented. The effects of some key parameters, i.e. nozzle diameter, printing speed as well as filler loading, on the alignment level of hBN are also investigated. Finally, the alignment level of the platelets is predicted by effective medium approximation, which is consistent with that measured by small angle X-ray scattering.