Ultrathin and anisotropic polyvinyl butyral/Ni-graphite/short-cut carbon fibre film with high electromagnetic shielding performance

Ultrathin, flexible and anisotropic polyvinyl butyral (PVB)/graphite coated with nickel (Ni-Gr)/short-cut carbon fibre (SCF) cast films were fabricated using a convenient solution casting method. The effects of the filler components, contents, and their distribution structures on the electromagnetic shielding effectiveness (SE) of the composites are investigated. The results indicate that the hybridisation and distribution of fillers with different shapes could significantly improve the electromagnetic shielding performance. The anisotropic SE of the composites is due to the orientation of the SCFs in the casting direction, which was induced by the traction from the carrier tape of the casting machine. Moreover, the measured electromagnetic SE in the perpendicular direction was higher than that in the casting direction. The experimental results showed that the prepared composite films had excellent anisotropic SE in the measured frequency range of X band. The SE and specific SE of the PVB/Ni-Gr/SCF cast film with a mass ratio of 69/26/5 are 32 dB and 159 dB/mm, and 20 dB and 101 dB/mm, across and along the casting direction, respectively. The SE difference between the two directions of the microwave shielding material provides the potential to prepare a direction selective composite with an ultrahigh electromagnetic shielding performance. Moreover, the prepared composites showed great potential as microwave shielding materials in military and civilian applications.