Development of Lightweight and Flexible Carbon Nanofiber and Polyurethane Nanocomposite for EMI Shielding Applications

Future-generation EMI shielding requires thin, flexible, stretchable nanocomposite structures for conformal, flexible and bendable electronic appliances that can sustain harsh environmental conditions. The present work shows the design and development of such type structures by encapsulating carbon nanofiber (CNF) inside polyurethane (PU). The 8 wt% CNF (CNF8) shows improved conductivity and EMI shielding effectiveness (SE) in the X-band (8.2 to 12.4 GHz). The maximum total SE (SE
T
) of 34.41 dB for CNF8 is observed at 0.75 mm thickness, unaffected by the complex environmental conditions like two hours of water sonication, 1000 mechanical bending cycles, and horizontal and vertical bending. The microstructure and electrical conductivity profile of these fabricated structures are used to explain the absorption dominating the EMI shielding process. Further, the layers of CNF8 are stacked together with the help of solvent followed by mechanical pressing, and the maximum SE
T
of 71.61 dB was achieved for a thickness of 2.21 mm. For a broadband EM shielding application, the SE
T
is calculated theoretically via simulation in CST microwave studio. The fabricated flexible, lightweight nanocomposite structures exhibit good EMI shielding and can be used in conformal surface coating and electronic packaging in defence, and aerospace applications.