Preparation And Properties Of Natural Rubber Based Magnetic Shielding Composite

In recent years,with the demand of intelligent,lightweight and wearable intelligent electronic devices for electromagnetic protection,polymer matrix composite materials are widely used in electromagnetic shielding field.Compared with traditional metal materials,polymer matrix composites have the advantages of good processing,low density,adjustable conductivity and corrosion resistance.However,most of the polymer matrix itself has insulation,which seriously limits its application in electronic products,new energy vehicles,medical devices,flexible circuit boards and other fields requiring high electromagnetic shielding performance.At present,the most common solution is to enhance electromagnetic shielding performance by compounding conductive filler with polymer matrix to give it high conductivity.As the most common polymer material,natural rubber has been widely used in the fields of national defense,military industry and scientific research due to its excellent machinability,high elasticity and excellent mechanical properties.Will be simple blending conductive filler and natural rubber matrix can effectively improve the conductivity and electromagnetic shielding performance,but the traditional way of processing usually has higher than threshold,need a lot of conductive filler will make its excellent conductivity and electromagnetic shielding performance,but the increase of filler content tend to make rubber hard to form perfect crosslinking network,As a result,its mechanical properties are affected,the cost is increased and the applicability of the material is reduced.Therefore,in this paper,an effective three-dimensional conductive network is constructed in the natural rubber matrix by prefabricated template method,and the original excellent mechanical properties of natural rubber are retained to the maximum extent,so as to obtain natural rubber-based electromagnetic shielding composite material with excellent mechanical properties.Relevant research contents are as follows:(1)The graphene oxide 3D network composite foam(GO/PDA/MF)was prepared by adhering to the graphene oxide(GO)using melamine foam(MF)modified by polydopamine(PDA)as 3D network template(PDA/MF).After high temperature treatment,PDA/MF composite foam was carbonized and GO was reduced to obtain r GO aerogel.Then,natural rubber(NR)was impregnated by vacuum assisted method to prepare r GO/NR composite with three-dimensional conductive network.A three-dimensional conductive network was efficiently constructed in NR matrix by prefabricated template method.By increasing the impregnation times of PDA/MF composite foam in GO dispersion,the excellent conductive properties were endowed.The principle of impedance mismatch was used to make the composite material possess electromagnetic shielding properties and retain the excellent mechanical properties of NR.The experimental results show that the conductivity,EMI SE and tensile strength of r GO/NR composite are 9.58 S/m,20.5 d B and 14.7 MPa when the composite foam is immersed in GO dispersion for 4 times(3.8wt %).(2)The CNT/PDA/MF composite foam was prepared by electrostatic adsorption of carbon nanotubes(CNT)modified by sodium dodecyl sulfonate(SDS)and PDA/MF.CNT aerogel(CNT/c MF)was obtained by high-temperature carbonization template using the method in(1)above.Then NR was backfilled to prepare CNT/NR composites with three-dimensional conductive network structure.Due to the conductivity of the carbon residual network after carbonization of PDA/MF composite foam and the excellent conductivity of CNT itself,the composite material has higher conductivity and electromagnetic shielding performance.However,the mechanical properties of the composite material decrease due to the poor compatibility between CNT/c MF aerogel and matrix.The experimental results show that the conductivity,EMI SE and tensile strength of CNT/NR composites are 12.37 S/m,24.1 d B and 12.3 MPa when the composite foam is impregnated in CNT dispersion for 4 times.(3)The GO-CNT/PDA/MF composite foam with laminated network structure was constructed on PDA/MF skeleton by using the method of cetyltrimethylammonium bromide(CTAB)modified CNT and GO in the manner of electrostatic self-assembly.Rgo-cnt aerogel was obtained by carbonizing PDA/MF composite foam by the method in(1)above.r GO-CNT/NR composites were prepared by backfilling NR.The synergistic effect between GO and CNT is more conducive to the formation of conductive network,which further improves the conductivity and electromagnetic shielding efficiency of composite materials and maintains the mechanical properties of NR to a certain extent.The experimental results show that the conductivity of r GO-CNT/NR composite is 30.57 S/m,EMI SE is 30.4 d B and tensile strength is 14.5 MPa when the composite foam is soaked in GO dispersion and CNT dispersion for 4 times(3.8wt %).