Eco-friendly preparation and characterization of highly thermally conductive polyimide/boron nitride composites

In this paper, we report the eco-friendly preparation of polyimide/boron nitride (PI/BN) composite sintered materials and the characterization of their thermally conductive properties. First, monomer salt (MS)/BN composite powders were synthesized using a green solvent (water and acetone mixture). Next, PI/BN composite powders were synthesized by solvent-free solid-state polymerization (SSP) of MS/BN. Finally, thermally conductive specimens were prepared through solvent-free sintering of PI/BN powders. The PI/BN composite specimens showed high in-plane and out-of-plane thermal conductivities (2.777 and 0.962 W/mK, respectively). Thermal conductivities of the specimens increased 558 % (in-plane) and 483 % (out-of-plane) compared to a pure-PI specimen. We found that ultrasonicated fine BN nanosheets adhered to angular surface of PI particles, leading to effective connections between the BN nanosheets during compression. Our study provides a novel eco-friendly and economical preparation method for highly thermally conductive PI composites.