Heterolayered Composite of Carbon Nanofibers Sandwiched between Poly(ethylene terephthalate) and Polyurethane for Flexible Electromagnetic Shielding Application

Multifunctional flexible films having properties of low filler dosing, light weight, small thickness, excellent environmental stability, and durability are highly demanded for absorption dominant electromagnetic interference (EMI) shielding in wearable electronic gadgets and in electronic packaging for civil, military, and space applications. For this, layered flexible films (FFs) of poly(ethylene terephthalate) (PET), carbon nanofibers (CNFs), and polyurethane (PU) were fabricated. The sheet resistance decreased from 48.9 × 103 to 8.3 × 102 Ω/cm2 on increasing the CNF wt %, which resembled an improved 3D CNF network. This 3D CNF network was developed to achieve a total shielding efficiency (SET) of ∼25 dB (>99.9%) at 2 wt % for just 0.5 mm thickness of the film. Importantly, the fabricated film showed exceedingly consistent EMI shielding performance in a complex environment, with 22.9 dB and 23.6 dB SET values even after 1 h of ultrasonication treatment in water and 10 000 mechanical bending cycles, respectively. Conveniently, owing to the increased interfacial polarization, conduction loss, and multiple reflections, these FFs exhibited efficient EMI shielding accommodating the absorption dominant mechanism. The EMI shielding was also numerically analyzed through CST microwave studio software over the broad frequency range of 1–18 GHz. This work contributes to the fabrication and study of layered flexible films to enhance mechanical properties and achieve high absorption dominant EMI shielding for future-generation portable/wearable gadgets and packaging applications.