Highly Multifunctional and Thermoconductive Performances of Densely Filled Boron Nitride Nanosheets/Epoxy Resin Bulk Composites
Kun Fu, Jingwen Yang, Chaochao Cao, Qinghong Zhai, Wei Qiao, Jiaxiao Qiao, Hejun Gao, Zheng Zhou, Jiawei Ji, Mengyuan Li, Chaoze Liu, Bozheng Wang, Wenjuan Bai, Hongliang Duan, Yanming Xue, Chengchun Tang
Abstract
In the development of hexagonal boron nitride (h-BN)-based polymeric composites with high thermal conductivity, it is always challenging to achieve a dense filling of h-BN fillers to form a desired high-density thermal transfer network. Here, a series of boron nitride nanosheets (BNNSs)/epoxy resin (EP) bulk composites filled with ultrahigh BNNSs content (65–95 wt %) is successfully constructed through a well-designed mechanical-balling prereaction combined with a general pressure molding method. By means of this method, the highly filled BNNSs fillers are uniformly dispersed and strongly bonded with EP within the composites. As a result, the densely BNNSs-filled composites can exhibit multiple performances. They have excellent mechanical properties, and their maximum compression strength is 30–97 MPa. For a BNNSs/EP composite with filling ultrahigh BNNSs fraction up to 90 wt %, its highly in-plane thermal conductivities (TC) are 6.7 ± 0.1 W m–1 K–1 (at 25 °C) to 8.7 ± 0.2 W m–1 K–1 (200 °C), respectively. In addition, the minimum coefficient of thermal expansion of BNNSs/EP composites is 4.5 ± 1.3 ppm/°C (only ∼4% of that of the neat EP), while their dielectric constants are basically located between 3–4 along with their dielectric loss tangent values exceptionally <0.3 in the ultrahigh frequency range of 12–40 GHz. Additionally, these BNNSs/EP composites exhibit remarkable cycle stability in heat transfer during heating and cooling processes because of their structural robustness. Thus, this type of densely BNNSs-filled BNNSs/EP composite would have great potential for further practical thermal management fields.