Flexible TPU/MWCNTs/BN composites for frequency-selective electromagnetic shielding and enhanced thermal conductivity

With the miniaturized and high-frequency of electronic devices, multifunctional composites with high electromagnetic interference (EMI) shielding effectiveness (SE), thermal conductivity and insulation are urgently demanded. In this work, sandwich-structured TPU/MWCNTs/BN multifunctional composites with segregated interlayer were prepared successfully. Characterization results confirm the formation of sandwich structure in whole and segregated structure in interlayer. This unique structure endows the composites frequency-selectively EMI SE, high thermal conductivity, and insulation in the shielding direction. For example, C5-sBN40T1.3, with the 5 wt% MWCNTs dispersed in the surface layer and 40 wt% BN dispersed in the interlayer, showing the average and maximum EMI SE of 41.41 dB and 46.12 dB, respectively, 2.96 and 3.20 times of samples without interlayer. Meanwhile, the thermal conductivity can reach 0.7594 W/(mK), 3.30 times of pure TPU. The electromagnetic shielding peak and thermal conductivity can be tuned by adjusting the thickness of the interlayer and the content of the filler. This work provides an ingenious strategy for fabricating multifunctional polymerbased composites.