High Thermally Conductive and Electrical Insulating “Sandwich” Structured Composites Fabricated by Hot-pressing of PEEK Film Combined with fBNNSs@fMWCNT/SPEEK Membrane via Electrospinning

With the rapid development of 5 G technology, the heat dissipation of electronic devices has become an important challenge. It is particularly essential to construct efficient thermal transfer networks in order to obtain advanced materials with superior thermal conductivity as well as excellent electrical insulating properties. In this work, poly (ether ether ketone) (PEEK) was sulfonated to achieve its solubility for electrospinning. Multi-scale hybrid fillers containing hydroxylated boron nitride nanosheets (fBNNSs) and carboxylated multi-walled carbon nanotubes (fMWCNT) are aligned along the direction of sulfonated PEEK (SPEEK) fibers during electrospinning process where fMWCNT with high aspect ratio can be used as mediators to connect the dispersed fBNNSs resulting in synergistic effect to extensively improve the thermally conductive performance. The hydrogen bond interaction among sulfonic acid group, carboxy groups and hydroxy groups from the matrix and modified fillers can not only make the fillers disperse uniformly but also improve the interfacial properties, thus reducing the phonon scattering at the interface efficiently, to enhance the thermal conductivity significantly at relatively low filler loading. fBNNSs@fMWCNT/SPEEK composite exhibits excellent thermal conductivity (λ) of 5.25 W/(m·K) when the filler content reached by 26 wt% with the ratio of fBNNSs to fMWCNT of 25:1(wt:wt). Under the composition above, the excellent electrical insulating property (2.54×1015Ω·cm) is achieved as well. Furthermore, fBNNSs@fMWCNT/SPEEK fiber membrane can be used as thermally conductive filler to construct a "sandwich" structured composite with PEEK film. When the mass ratio is 1:1, the λ of composite is 3.1 W/(m·K), which is 1200% higher than that of PEEK. This work provides better understanding of PEEK based thermal conductive composites for the prospective application of thermal management materials in electrical insulating related fields.