Reduced graphene oxide deposited carbon fiber reinforced polymer composites for electromagnetic interference shielding

Abstract

Reduced graphene oxide deposited carbon fiber (rGO-CF) was prepared by introducing GO onto CF surface through electrophoretic deposition method, following by reducing the GO sheets on CF with NaBH₄ solution. The rGO-CF was found to be more effective than CF to improve the electromagnetic interference (EMI) shielding property of unsaturated polyester (UP) based composites. With 0.75% mass fraction of rGO-CF, the shielding effectiveness of the composite reached 37.8 dB at the frequency range of 8.2–12.4 GHz (x-band), which had 16.3% increase than that of CF/UP composite (32.5 dB) in the same fiber mass fraction. The results suggest that rGO-CF is a good candidate for the use as a light-weight EMI shielding material.

Introduction

Carbon materials reinforced polymer composites have been applied in many fields, such as sensors, fuel cells, water treatment, electromagnetic interference (EMI) shielding and microwave absorption [1], [2], [3], [4]. Carbon black, graphite, graphene, carbon nanotubes (CNT), carbon fiber (CF), and carbon nanofiber (CNF) have been popularly employed [5], [6], [7], [8], [9], [10], [11], [12], [13]. Among these materials, CF is primarily preferred for EMI shielding materials due to its excellent electrical property, large aspect ratio and high thermal stability [14], [15]. However, CF possesses high resistivity and brittleness in nature, consequently limiting its application in the EMI composites [16]. There are normally two methods to solve the aforesaid problems. One is introducing nanofillers such as CNT and graphene into the matrix of composites [17], [18]. Hong et al. [19] synthesized polypropylene composite reinforced by 30% mass fraction of CF with the length of 200–250 μm and 1% mass fraction of CNT. The result showed the best EMI shielding effectiveness (SE) value was around 16 dB. However, the poor adhesion in composite was still the limiting factor for the enhancement in SE of the composite [20]. Another way is electroplating a thin layer of metal on the surface of CF, which also holds great promise for obtaining better SE of the composite [21]. Wang et al. [22] fabricated nickel coated CF (Ni-CF) reinforced silicone rubber composites for EMI shielding applications, and attained a high SE of 80 dB at the frequency range of 30–1200 MHz in the silicone rubber composite with 80 phr Ni-CF.

Graphene, graphene oxide (GO) and reduced graphene oxide (rGO) have inspired enormous interests due to nanometer-thick two-dimensional structure and remarkable electrical and mechanical properties [23]. Researchers have studied the applications of them in the field of EMI shielding. Liang et al. [24] reported a maximum of 21 dB shielding of electromagnetic energy, where the frequency band was from 8 GHz to 12.8 GHz, via a graphene/epoxy composite with 15% mass fraction of graphene concentration. Zhang et al. [25] prepared functional polymethylmethacrylate (PMMA) nanocomposite microcellular foams with graphene sheets reinforcement, and the results showed that the conductivity and SE of the foam achieved 3.11 S/m and 19 dB respectively with only 5% mass fraction of graphene sheets. Yousefi et al. [26] reported a highly aligned rGO reinforced epoxy nanocomposites with unique anisotropy electrical and mechanical properties. The nanocomposite with 2% mass fraction of rGO presented a remarkable shielding efficiency of 38 dB.

The fiber coating technologies have been developed many years ago for various purposes [27], [28], [29], and carbon nanomaterials such as CNT and graphene have given rise to a significant improvement in tensile strength, electrical properties and barrier performance of fiber. Huang et al. [30] attached GO onto the surface of CF by electrophoretic deposition method and rGO obtained by subsequent annealing process, which improved the interfacial property and mechanical properties of CF/polymer composites. However, few reports about GO-CF and rGO-CF on the effect on EMI shielding characteristics of composites have been reported. Furthermore, little research has concerned the EMI shielding mechanisms of GO-CF and rGO-CF reinforced polymer composites. The aim of this study is to investigate the effect of fiber content on EMI shielding property of unsaturated polyester (UP) matrix composite. The study further aimed at studying the roles of GO and rGO in improvement of the shielding property and elaborating EMI shielding mechanism of GO-GF/UP and rGO-CF/UP composites. Motivated by these above, four types of samples; namely pristine UP, CF/UP composite, GO-CF/UP composite and rGO-CF/UP composite were prepared using casting molding technique, and the mass fractions of fiber in resin varied from 0.25% to 1.00%.