Fusing-smashing exfoliation for high-aspect-ratio hexagonal boron nitride nanosheets available to highly-thermoconductive polymeric composites

In the development of hexagonal boron nitride (h-BN)/polymer composites, it is expected that efficient thermal transport networks constructed by the desired high-aspect-ratio (HAR) h-BN nanosheets (BNNSs) can be formed within them, thereby enhancing their heat dissipation capacity. In this work, a new and facile fusing-smashing method was developed to exfoliate h-BN. This method produces BNNSs with an outstanding aspect ratio of about 2200. Using these HAR-BNNSs as fillers, a series of BNNSs-based polymer composites were developed in the form of bulks, films, and adhesives with high thermal conductivity (TC) and mechanical performance. The maximum room temperature TC and compressive strength values of the formed 30BNNSs/rosin bulk composites are 3.13 ± 0.08 Wm^-1k⁻¹ and 64 MPa, respectively. They show 62.6 times and 3.6 times the performance of the blank rosin. The in-plane TC and tensile strength of the 22BNNSs/Polyimide (PI) films are 14.4 ± 0.1 Wm^-1k⁻¹ and 60 MPa, respectively, which are higher than those of the blank PI film (0.18 Wm^-1k⁻¹ and 30 MPa). Noteworthy, compared to the blank adhesive of SMT (soyoil-malate-tannin), the TC of the prepared 2.5BNNSs/R/SMT composite adhesive is increased by 3.7 times, while its bonding strength also exhibits a 22 % enhancement, with only 2.5 wt% HAR-BNNSs filling fraction. In addition, all the HAR-BNNSs-filled composite materials manifest exceptional thermal diffusivity, indicating their potential for widespread application in thermal management for modern electronic devices.