Study On The Preparation And Electromagnetic Shielding Properties Of Polymer-Matrix/Graphene Composites

With the practical application of electromagnetic shielding materials,the requirement of light density and high efficiency has been improved.Compared with the metal based electromagnetic shielding materials,polymer/graphene composites materials have many advantages in the field of electromagnetic shielding,such as low density,good corrosion resistance,easy processing,good flexibility and controllability of the electromagnetic shielding performance.Because of the high conductivity and special two-dimensional layered nanostructures,graphene can overlap with each other to form a continuous conductive network structure.Graphene and its modified derivatives are an excellent electromagnetic shielding functional filler with excellent performance,in the field of basic research and applied research.In view of the disadvantages of metal based electromagnetic shielding materials,such as high density and difficult to be machined.In this paper,the polymer/graphene composites were prepared,using different layers of graphene and doped modified graphene as electromagnetic shielding functional fillers,and low density polymer materials as the matrix.The application of the composites in the ultra high frequency(1-12 GHz)electromagnetic shielding were investigated.It is an important condition for polymer matrix composites to exhibit the electromagnetic shielding properties,different layers of graphene forming a continuous conductive network structure in the polymer matrix.Using different synthesis methods,the uniform dispersion and its forming a continuous conductive network structure of the functionalized graphene fillers with different layers in the polymer matrix,can be effectively controlled,in order to achieve the desired electromagnetic shielding performance.The electrical conductive properties,morphology and structures,electromagnetic shielding properties,and thermal properties of the composites were analyzed,to explore the connection between structure and electromagnetic shielding properties of polymer based composites and its rules,the influence of different layers of graphene on the electromagnetic shielding properties of composites,and simple and effective preparation method of polymer/graphene composites.The research contents of this paper are as follows:(1)Using waterborne polyurethane(WPU)as the polymer matrix,and diethylenetriamine(DETA)as a reducing agent and N-doping agent.N-doped reduced graphene oxide/waterborne polyurethane(NRGO/WPU)composites were successfully prepared by in situ chemical reduction of graphene oxide(GO)in an aqueous solution system.The results show that:not only was simultaneous chemical reduction and N-doped functionalization of GO realized,but the uniform distribution of NRGO in the WPU matrix was also achieved.Furthermore,NRGO formed a continuous network structure in the polyurethane matrix.With the increase of NRGO content,the electrical conductivity and electromagnetic shielding properties of the composites were obviously enhanced.The best electrical conductivity of the NRGO/WPU composites was 0.08 S/cm with 12 wt%NRGO content.Furthermore,the composites exhibited the corresponding EMI shielding effectiveness of 28.3 dB.In addition,the NRGO/WPU composites have good thermal stability.(2)Using poly(vinylidene fluoride)(PVDF)as the polymer matrix,and few-layer graphene sheets(FGS)as electromagnetic shielding functional filler,few-layer graphene sheets/poly(vinylidene fluoride)(FGS/PVDF)composites were successfully prepared by a water vapor induced phase separation(WVIPS)method.The results show that:the uniform distribution of the FGS and their formation of a continuous network structure were realized by the WVIPS method.With the increase of the FGS content,the electrical conductivity and electromagnetic shielding properties of the composites are obviously enhanced.The best electrical conductivity of the FGS/PVDF composites was 1.68 S/cm with 15 wt%FGS content.Furthermore,the composites exhibited the corresponding EMI shielding effectiveness of 45.6 dB at 10 GHz.The FGS/PVDF composites have good thermal stability.In addition,the WVIPS method was found to be an easy,novel and efficient synthetic route to prepare FGS/PVDF composites,that can also be used in the preparation of FGS and other polymer matrix composites.(3)Using silicone rubber(PDMS)as the flexible polymer matrix,and industrial grade multi-layer graphene sheets(MGS)as electromagnetic shielding functional filler,multi-layer graphene sheets/silicone rubber flexible(MGS/PDMS)composites were successfully prepared by in situ polymerization method.The results show that:the MGS/PDMS flexible composites have good flexibility.The uniform distribution of the MGS and their formation of a continuous conductive network structure were realized.With the increase of the MGS content,the electrical conductivity and electromagnetic shielding properties of the flexible composites are obviously enhanced.The electrical conductivity of the flexible composites was 0.12 S/cm with 20 wt%MGS content.Furthermore,the composites exhibited the corresponding EMI shielding effectiveness of 21.4 dB at 10 GHz.The MGS/PDMS composites have good thermal stability.In addition,the preparation process is a simple and effective method for the preparation of MGS/PDMS flexible composites material,enriching the preparation and research of flexible electromagnetic shielding composite materials.