Preparation of polymer composites with high thermal conductivity by constructing a “double thermal conductive network” via electrostatic spinning

With the advancement of information technology, there is a boom of demand for high-performance thermal conductive polymer-based materials applied in microelectronic devices. Fillers with high thermal conductivity, such as boron nitride nanosheets (BNNS), are often incorporated to improve the comprehensive thermal conductivity of polymer matrix. However, the fillers dispersed in composites often fail to form continuous heat transfer pathways due to the occurrence of interfaces, resulting in a suppressed thermal conductivity. In this paper, BNNS was confined in carbon nanofibers by electrostatic spinning (e-spin). The resultant fibrous carbon-boron nitride hybrid skeleton was combined with silicone rubber to form an elastic composite film. The effects of BNNS contents on the hybrid skeleton morphology and the composite conductivity were rigorously resolved. It was found that the hybrid skeleton consisted of continuous long-stacked carbon fibers, with high thermal conductivity intrinsically. And BNNS was tightly stacked, confined, and oriented along the fibers. The maximum thermal conductivity of the composite film was 4.09 W m−1 K−1, about 16 times higher than that of pure PDMS. A double thermal conductive network mechanism was proposed. That is, the two thermal pathways were formed by the overlapped BNNS and the carbon fibers, respectively. And the optimal thermal conductivity was achieved as the two pathways composited together by spinning and carbonization. The composite films with vertical alignment of the hybrid fibers were also prepared. Our work provides an essential and innovative strategy for the preparation of high thermal conductivity composites.