Enhancing Electromagnetic Interference Shielding Effectiveness of Polymer Nanocomposites by Modifying Subsurface Carbon Nanotube Distribution

Abstract

Enhancing electromagnetic interference (EMI) shielding effectiveness (SE) of polymer nanocomposites (PNCs) relies on modification of carbon nanotube (CNT) distributions achieved by controlling fabrication parameters. However, establishing correlations between fabrication parameters, CNT distributions, and SE properties is a challenging task due to the restrictions on the traditionally implemented CNT network detection techniques and qualitative CNT distribution descriptors. Herein an SE enhancing methodology for single‐walled carbon nanotubes/polyimide (SWCNT/PI) nanocomposite films in which AC sinusoidal voltages (5, 10, and 15 V at 10 Hz) are applied during processing to control CNT distribution is presented. The prepared nanocomposite samples are characterized using scattering‐parameter measurements for SE estimation and second‐harmonic electrostatic force microscopy (2ωe‐EFM) for subsurface CNT network detection. The detected CNT networks are described by implementing the uniform‐distancing (CNTD), agglomeration (CNTA), and shielding (CNTS) quantitative CNT descriptors. The results show enhancement on the nanocomposite SE values with the increment on the CNTS descriptor, which increases with lower applied voltages during processing. The SWCNT/PI nanocomposite studied herein exhibits a predominant absorption SE mechanism, which makes it a candidate for potential EMI absorber material applications. The proposed methodology represents an alternative for the quantitative assessment of correlations between PNC properties, CNT distributions, and fabrication parameters.