Processing-Mediated Different States of Dispersionof Multiwalled Carbon Nanotubes in PDMS Nanocomposites Influence EMIShielding Performance

摘要

Advancement in wireless technology has increased the usage of wireless devices extensively in the past few years, which led to an increase in electromagnetic interference (EMI) in the environment. Extensive research on fabrication of EMI shielding materials has been done. However, the role of processing method of polymer composites in EMI shielding has been neglected. In this work, we investigate the role of two polymer processing methods, spin coating and compression molding, in EMI shielding application. Poly(dimethylsiloxane) (PDMS) nanocomposites with multiwalled carbon nanotube (MWCNT) were spin-coated onto glass slides and compression-molded to a similar thickness. The processing method that exhibited the best shielding was employed to fabricate multiple PDMS composites comprising different compositions of MWCNT and Fe3O4 and stacked to form a multilayered EMI shielding PDMS composite. Scanning electron micrographs revealed that MWCNT in spin-coated composites are significantly more agglomerated than in the compression-molded film. Direct current conductivity andcuring temperature were higher in compression-molded films as thefiller formed a well-percolated network and hindered cross-linkingof polymer chains. EMI shielding results revealed that spin-coatedfilms demonstrated greater shielding effectiveness than compression-moldedcomposites in the Ku-band (12–18 GHz). Individual agglomeratesof MWCNT in spin-coated film attenuated incoming electromagnetic radiationmore effectively than well-dispersed MWCNT in compression-molded films.Therefore, PDMS composites of different compositions of MWCNT andFe3O4 nanoparticles were prepared through spincoating and stacked with a gradient of filler concentration, whichresulted in maximum shielding of −28 dB, i.e., shielding morethan 99% of incoming EM radiation by a 0.9 mm film.