Study On Preparation And Eletromagnetic Shielding Property Of Polystyrene/Graphene/Fe₃O₄Composites

With the highly centralization, digitization, miniaturization of electronic equipments, the signal they transmit is susceptible to external electromagnetic radiation. Moreover, electromagnetic pollution also does great harm to people’s health. Recently, electromagnetic pollution has become a new major pollution after water pollution, air pollution and noise pollution. Therefore, preparing the composite, which has excellent EMI shielding performance is one of the most urgent researches.Graphene has many advantages, such as high electrical conductivity, large specific surface, low-density and so on. Therefore, it is an ideal electromagnetic shielding material. However, the shielding effectiveness of graphene is not very good in low frequency magnetic field. Compared with graphene, the materials with high permeability, such as ferrite, have a great shielding effectiveness in low frequency magnetic field. Hence, we use graphene and magnetic particles as fillers to prepare the polymer based composite with excellent EMI shielding, which has both magnetic loss and electrical loss. In this report, we use natural graphite, soluble iron and ferrous salt as raw materials to prepare graphene, Fe3O4particles and RGO/Fe3O4complex, whereafter we use these as fillers preparing polystyrene based composites, which both have the magnetism of Fe3O4and electroconductibility of graphene. The detailed contents are as follow:1. we use Staudenmaier method to prepare graphite oxide, and then adopt two methods (hydration hydrazine reduction and thermal expansion) to prepare two different graphene:RGO and TGO. Subsequently, we use respectively RGO and TGO as filler, polystyrene as matrix, to prepare PS/RGO and PS/TGO composites by solution mixing method. SEM indicates TGO can disperse well in PS matrix, while RGO will have obvious agglomeration. Therefore, the electrical conductivity and EMI shielding of PS/TGO composite are superior to those of PS/RGO composite.2. we adopt a simple method to prepare RGO/Fe3O4compolex by one-pot reaction using GO、FeSO4and FeCl3as starting materials. Graphene oxide was reduced to graphene (RGO) and Fe3O4particles were grown on the carbon basal planes simultaneously. Then, Using RGO/Fe3O4as filler, we prepare PS/RGO/Fe3O4composite by solution mixing. The results indicate that compared with PS/RGO composite, the electrical conductivity of PS/RGO/Fe3O4composite has not obvious improve, thereby no obvious improving on EMI shielding performance. 3. we use solvothermal reaction and co-precipitation methods to prepare Fe3O4particles with different size, and then Fe3O4particles were modified by silane coupling agent, which can introduce the functional groups to the Fe3O4particles. Moreover, we use the Fe3O4particles and thermal expansion graphene as fillers, polystyrene as matrix, to prepare three different composites:PS/TGO/Fe3O4-10, PS/TGO/Fe3O4-60and PS/TGO/Fe3O4-220. SEM indicates that the modified Fe3O4particles have a well compatibility with polystyrene, and disperse well in polystyrene. The results of electrical conductivity show that the addition of Fe3O4particles has no negative effect on the electrical conductivity of PS/TGO composite. Moreover, compared with PS/TGO, the EMI shielding of PS/TGO/Fe3O4composite are improved in different degrees.