No abstract

Thermal management has become a critical challenge in electronics and portable devices. To address this issue, polymer composites with high thermal conductivity (TC) and low dielectric property are urgently needed. In this work, we fabricated perfluoroalkoxy (PFA) composite with high anisotropic TC and low dielectric constant by aligning boron nitride nanosheets (BNNs) via hot pressing. We characterized the thermal stability, microstructure, in-plane and through-plane TCs, heat dissipation capability, and dielectric property of the composites. The results indicate that the BNNs–PFA composites possessed good thermal stability. When the BNNs content was higher than 10 wt %, the BNNs were well layer aligned in the PFA matrix, and the composites showed obvious anisotropic TC. The in-plane TC and through-plane TCs of 30 wt % BNNs–PFA composite were 4.65 and 1.94 W m−1 K−1, respectively. By using the composite in thermal management of high-power LED, we found that alignment of BNNs in composite significantly improves the heat dissipation capability of composite. In addition, the composites exhibited a low dielectric property. This study shows that hot pressing is a facile and low-cost method to fabricate bulk composite with anisotropic TC, which has wide applications in electronic packaging.

Incorporating hybrid fillers into polymer has been considered as one of the effective ways to obtain composites with high-thermal conductivities (TCs). Herein, we fabricated polytetrafluoroethylene (PTFE) composites by using micro-boron nitride nanosheets (mBNNs) and nano-BNNs (nBNNs) as fillers, and studied the optimum ratios of mBNNs to nBNNs (i.e., mBNNs:nBNNs) for obtaining high-thermal conductive composites at different filler's contents. The results indicated that for the composites with total BNNs contents of 10, 20, and 30 wt%, the optimum mBNNs:nBNNs for obtaining the highest TC were 9:1, 9:1, and 5:5, respectively. The highest TC of the composites with 30 wt% BNNs could reach 1.46 WÁm −1 ÁK −1 , which was 356% higher than that of PTFE. The reasons for optimum mBNNs:nBNNs values were interpreted by observing the composite's microstructures. Moreover, the fabricated composites also exhibited excellent electrical insulation properties. This study has important implications for obtaining high-thermal conductive composites using hybrid fillers.