Flexible and thermal conducting multi-walled carbon nanotubes/waterborne polyurethane composite film from in situ polymerization for efficient electromagnetic interference shielding

A flexible multi-walled carbon nanotubes (MWCNTs)/waterborne polyurethane (WPU) composite film was prepared via in situ polymerization followed by a facile blade coating process. An ultrahigh MWCNTs content of 48.1 wt% was obtained in this film, where MWCNTs without modification of acid or surfactant were uniformly dispersed in the WPU matrix. Therefore, the obtained film exhibited a high electrical conductivity of 16.67 S cm−1 and thermal conductivity of 5.31 W m−1 K−1. Moreover, an outstanding EMI SE of 65.3 dB at the frequency of 110 MHz was achieved with a film thickness of 80 μm, which can screen 99.9999% of incident wave at such frequency. The EMI shielding performance of this film is comparable to those of other polymer-based shielding composites with larger thickness (0.5–2 mm) ever reported. Furthermore, excellent flexibility and durability of composite films were demonstrated by bending test, indicating that it is a promising candidate for thermal conduction and EMI shielding of portable and wearable devices.