Abstract
The aim of this study is to prepare lightweight, flexible, two-dimentional Graphene Nano Sheets(GNS)/Polyamide 6,6 composites for electromagnetic interference(EMI) shielding by a dip coating process. The Polyamide 6,6 fiber networks were obtained by electrospinning, which will form lightweight, flexible, and high porous matrices. This study includes two parts. In the part one, GNS were adsorbed on the Polyamide 6,6 fiber surface, the diameter of Polyamide 6,6 fibers must be large enough for adsorption.The Polyamide 6,6 fibers with the diameter of 0.9~1.1 µm were prepared by controlling the parameters such as polymer concentration, collector distance and applied voltage in electrospinning. Graphene oxide(GO) was prepared from graphite by the modified Hummers’ method, and then was reduced to GNS-NaBH4 by NaBH4. In order to improve the dispersion of GNS-NaBH4, 1-Vinyl-2-Pyrrolidone (VP) was grafted onto the GO surfaces via the free Radical Polymerization to form PVP-GO, which was reduced to PVP-GNS-NaBH4 by NaBH4. According to the results of the analysis of XRD, XPS and TEM, it was confirmed that PVP was grafted onto GO surfaces. GNS-NaBH4 and PVP-GNS-NaBH4 were deposited on the surface of the Polyamide 6,6 fibers by a dip-coating approach, GNS-NaBH4/Polyamide 6,6 and PVP-GNS-NaBH4/Polyamide 6,6 composites were prepared. Surface electrical resistances of GNS-NaBH4/Polyamide 6,6 (3.46×106 Ω/sq) and PVP-GNS-NaBH4 /Polyamide 6,6 (9.9×105 Ω/sq) are decreased with the increasing of the time of dip coating. Electromagnetic interference(EMI) shielding effectiveness(SE) of PVP-GNS-NaBH4/Polyamide 6,6 was 9 dB. In the part two, in order to increase the electrical conductivity of composites, the degree of reduction of GNS must be enhanced. HI acid was substituted for NaBH4 to reduce GO. Furthermore, GNS was incorporated with silver nanoparticles(AgNps) to improve the electrical conductivity. GNS-HI/Polyamide 6,6 composites were fabricated by reducing GO/Polyamide 6,6 with HI acid. The surface resistance of GNS-HI/Polyamide 6,6 (62 Ω/sq) is lower than that of GNS-NaBH4 /Polyamide 6,6 (3.46×106 Ω/sq). The electromagnetic interference(EMI) shielding effectiveness(SE) was also improved to 16 dB from 5dB due to the high electrical conductivity of GNS-HI. In addition, GNS-HI /Polyamide 6,6 was incorporated with modified AgNps to form mAgNps -GNS-HI/Polyamide 6,6 composites. The mAgNps-GNS-HI/Polyamide 6,6 composite exhibits high performance in a sheet electrical resistance and electromagnetic interference(EMI) shielding effectiveness(SE) which are 33.9 Ω/sq and 31 dB, respectively.