Thermoset composites functionalized with carbon nanofiber sheets for EMI shielding

Carbon nanofiber sheets were developed through filtering well-dispersed carbon nanofiber (CNF) through filtering well-dispersed aqueous solution of CNF particles with 0.4 μm hydrophilic polycarbonate membrane by the aid of high-pressure air. They were used to functionalize composites by the resin transfer molding method. Their functionalized composites were characterized with scanning electron microscopy (SEM), four-point probes and a vector network analyzer to measure their morphologies, electrical conductivity, and electromagnetic interference (EMI) shielding performance over the frequency range of 8–12 GHz (X band), respectively. Their morphologies show that CNF particles are overlapped and tightly connected with each other in their interconnected networks. The CNF sheets are exposed on the surface, although their networks are partially penetrated by polyester resins. Their electrical conductivity can be 3.0 ± 0.2 Scm−1 or so, much higher by ten orders of magnitude than the reported electrical conductivity of CNF-filled composites. Their EMI shielding effectiveness slightly varies in a range of −30 dB to −35 dB as a function of frequency, much higher than that of most CNF or carbon nanotube–filled composites. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41873.