Effect Of Fabric Structure On The Performance Of Layer-by-layer Assembled (GO/PPy)_n Electromagnetic Interference Shielding Fabric

With the development of electronic devices,electromagnetic wave radiated by those devices will have a negative influence not only on electronic devices,but also on humans’ health.For this reason,there is a higher requirement for the development of electromagnetic interference(EMI)shielding materials.More and more attentions are paid on the influence of EMI shielding materials’ structure on their EMI shielding efficiency(SE).Porous materials will have an obviously positive influence on the EMI shielding due to the multi-reflections of electromagnetic wave between the interfaces.Fabric with porous structure has a huge advantage of being porous EMI shielding material due to its wide applications in the field of national defense,industry and domestic application.At the same time,porous fabrics have an advantage of structure on the preparation of high-efficiency EMI shielding materials.In this study,(GO/PPy)_n membrane are constructed on the surface of plain cotton fabrics with different yarn den sities via layer-by-layer assembly method,and EMI shielding fabric with different porous structure are obtained.A systematic study of the influence of fabric yarn density and sanding procedure on the EMI SE of fabrics are developed.(1)Firstly,the preparation and characterization of fabrics with different yarn densities are discussed,the parameters of yarn used in this study are also characterized,the weaving parameters are determined,and the morphology,tightness,pore size distribution and EMISE are investigated.The results indicate that the pore diameter decreases from 960.6μm to 22.3 μm with the yarn density increases from 70 picks/10 cm to 250 picks/10 cm.The pore size distribution indicates that fabrics have a hierar chical structure,with the increase of yarn density,the range of pore size distribution decreases and the hierarchical structure becomes less clear.The EMI SE of fabrics a re all lower than 0.6 d B,which indicates that those fabrics have little effect on EMI SE.(2)Secondly,(GO/PPy)_n EMI shielding membrane are constructed on the surface of fabrics with different yarn densities via layer-by-layer assembly method.First,The dispersion of graphene oxide(GO)is prepared via ultrasonic dispersing process and characterized by XRD.Then,(GO/PPy)_n EMI shielding fabrics with different pore stru cture are obtained by constructing the assembly unit GO and polypyrrole(PPy)on the fabrics.The results indicate that(GO/PPy)_n fabrics retained the original structure of fabrics,and their flexibilities had little changed.The pore size distribution of(GO/PPy)3 fabrics became a little smaller than pristine fabrics,however,the hierarchical structure is kept.The surface resistance decreases first then stay the same with the in crease of yarn density,however,the EMI SE increases then decreases with the increa se of yarn density.The main mechanism of shielding is absorbance,and the variation of EMI SE is due to the variation of absorbance part.(3)The influence of sanding procedure on morphology,surface resistance and EMI SE are discussed.The results indicate that the fiber bundle on the surface of fabric has been loosen by sanding procedure.The surface resistance of sanded fabrics is decreased and the EMI SE increased compared with fabrics without sanding,however,the surface resistance and EMI SE variation of sanded fabrics is similar to fabricswithout sanding,which indicates that the electrical conductivity and EMI SE of sanded fabrics is higher than fabrics without sanding.By analyzing the shielding factor,the increase of EMI SE of sanded fabrics is mainly due to the increase of absorbance.In this thesis,the influence of factors such as yarn density and sanding procedure on EMI SE of plain cotton fabrics are discussed,and the result shows that with the increasing of yarn density,the conductivity of fabric is increasing then maintaining constant,the EMI SE of fabric is increasing then decreasing;sanding procedure can enhance the EMI SE of fabrics.New guidance for the adjustment of EMI shielding fabrics performance are offered by the study of the influence of yarn density and sanding procedure on EMI SE of fabrics.