Abstract
The aim of this study is to prepare the electromagnetic interference shielding (EMI SE) polymer composite by two-dimentional Graphene Nano Sheets (GNS) and Waterborne Polyurethane (WPU) via solution mixing method. This study includes two parts. In the first part, graphene oxide (GO) was prepared from graphite by modified Hummers’ method, and then was reduced to GNS by NaBH4. In order to improve the dispersion and to prevent the restacking and aggregations of GNS during reduction, [2-(Methacryloyloxy)-ethyl]- trimethyl ammonium chloride (AETAC) was grafted onto the GO and GNS surface by free radical polymerization to form FGO and FGNS. FGO was reduced to FRGO by chemical reduction with NaBH4. According to the results of analysis of XRD, XPS and TEM, it was confirmed that AETAC was grafted onto GO and GNS surface. A simple solution mixing method was used to prepare GNS/WPU, FGNS/WPU and FRGO/WPU composite with 1, 3, 5 and 10 wt% filler content. The electrical conductivity of GNS/WPU (FGNS/WPU and FRGO/WPU) composites was increased with the filler content. The results showed that the highest electrical conductivity of 2.07 S/cm and EMI shielding effectiveness (EMI SE) of approximately 17 dB in the frequency of 8.2–12.4 GHz (X-band) were obtained by the 10 wt% filler content of FRGO/WPU composite. In the second part, in order to increase the electrical conductivity and EMI SE of composites, silver nanoparticles (Ag NPs) were deposited on the FRGO surfaces to form Ag@FRGO. The different weight ratios of Ag NPs to FRGO were 1：1, 1：3, 1：5 and 1：10, which formed 1Ag@FRGO, 3Ag@FRGO, 5Ag@FRGO and 10Ag@FRGO. A simple solution mixing method was used to prepare Ag@FRGO/WPU composites with 10 wt% filler content and different weight ratios of Ag NPs to FRGO. Results showed that the electrical conductivity and EMI SE of Ag@FRGO/WPU composites were increased with the increasing weight ratio of Ag NPs to FRGO. The highest electrical conductivity and EMI SE of 10Ag@FRGO/WPU composite over the frequency of 8.2–12.4 GHz were improved to 25.5 S/cm and 35 dB, respectively.