Preparation of sandwich-structured thermally conductive and insulating composite materials based on electrospinning combined with hot pressing technology

In this paper, h-BN was firstly exfoliated into functionalized BNNS by ball milling and liquid phase exfoliation techniques. BNNS/PVA composite fiber film was subsequently obtained by electrostatic spinning to realize the directional arrangement of BNNS in the PVA matrix, and BNNS/PVA/PS composite film was obtained by filling the pores inside the fiber film with PS solution. To further improve the thermal conductivity of the composite, carboxylated MWCNT was selected as the second thermally conductive filler, and the MWCNT/PVA/PS composite film was prepared by the same preparation method as BNNS/PVA/PS composite film. Finally, the MWCNT/PVA/PS composite film was placed in the middle layer, the BNNS/PVA/PS composite film was placed in the outer layer, and the thermally conductive composite materials with a novel sandwich structure were obtained by lamination. The combination of electrostatic spinning and hot pressing technology enabled the efficient construction of a high thermal conductivity network with BNNS and MWCNT, and the sandwich structure achieved a balance between high thermal conductivity and electrical insulation. The composite achieved a significant improvement in its in-plane thermal conductivity due to the realization of the directional arrangement of the filler in the in-plane direction. At a filler content of 14.75 wt%, the in-plane thermal conductivity of the composite was increased to 4.69 W/mK, which is nearly 23 times higher than that of the pure polymer. Due to the strict control of the spatial distribution form of MWCNT, the composites still have excellent insulation properties even at high filler content.