| Electromagnetic shielding materials are a measure to prevent electromagnetic waves from propagating in space or to prevent electromagnetic waves from entering the protective space.Generally,high-frequency electromagnetic shielding is realized by using a material having a certain electrical conductivity,and low-frequency electromagnetic shielding is realized by using a material having a certain magnetic permeability.These materials are basically hard metal materials.With the miniaturization of electronic components,the diversification of equipment shapes,and the development of electromagnetic shielding materials,the electromagnetic shielding materials have been demanded for flexibility and flexibility,and are required to be lightweight and broadband.It is necessary to develop an electromagnetic shielding material with elasticity,that is,the electromagnetic shielding performance is not lowered with stretching,so as to improve the dimensional adaptability of the electromagnetic shielding material,and to meet the shielding requirements such as diversified equipment shapes.This project is based on the development and performance study of elastic electromagnetic shielding fabrics of stainless steel blended yarns.The spandex yarn is used as the core yarn,and the stainless steel/cotton blended yarn or silver-plated yarn is wrapped to form elastic conductive yarn.With these yarns,According to a certain rule,the elastic electromagnetic shielding fabric is woven;the mechanical properties of the elastic conductive yarn,the fabric,the strain-resistance relationship,and the strain-electromagnetic shielding effectiveness relationship are systematically investigated.The feasibility of the elastic conductive fabric is predicted,and the fabric is different.Electromagnetic shielding effectiveness under elastic elongation conditions and its influencing factors.mainly includes:(1)Preparation of elastic electromagnetic shielding yarn and its strain-resistance relationshipPreparing a series of elastic stainless steel blended yarns by using spandex yarn as core yarn,outsourcing stainless steel/cotton blended yarn,and stainless steel/cotton blended spandex covered yarn;combining silver-plated yarn with spandex yarn to prepare plating Silver composite elastic yarn.Using Instron 5566,the mechanical properties of the yarn were tested to test the elongation at break of the yarn and the elastic recovery of the elongation at repeated stretching to study the elastic properties of the yarn.The combination of the multimeter and Instron 5566 was used to test the electrical properties of the yarn under different tensile conditions,that is,the change in electrical resistance,and to study the strain-resistance relationship of the yarn.From these data,the feasibility of preparing an elastic conductive fabric is predicted.The results show that the spandex yarn is the core yarn,and the stainless steel/cotton(SS/C)blended yarn is the outer yarn.The stainless steel fiber covered yarn is used to greatly improve the elasticity of the yarn,but the presence of spandex yarn affects the stainless steel.The contact between the fibers makes the resistance slightly lower than the SS/C blended yarn of the same stainless steel content;the stainless steel staple fiber in the yarn has a weakening effect on the elasticity,the content is high,the resistance is low,and the elasticity is poor.During the stretching process,the resistance of the 30% stainless steel covered yarn is less than 20% stainless steel covered yarn regardless of the tensile strain stage.The resistance of both yarns increases with strain,and then increases first and then decreases.The contact state of stainless steel fibers in the yarn directly affects the size of the resistor.The SS/C ammonia-coated yarn is plied with cotton/ammonia or spandex,and the obtained ammonia yarn is reduced in electrical resistance and has good stability.From this,it can be seen that the above test of the elastic yarn shows that it is feasible to prepare an elastic conductive fabric.(2)Preparation of elastic electromagnetic shielding fabric and its shielding effectivenessThe series of conductive yarns such as SS/C ammonia-coated yarn,SS/C blended yarn and SS/C ammonia-bonded yarn prepared above are formed into a series of weft-direction elastic,warp and weft double-elastic electromagnetic shielding fabric according to a certain weaving method,and the fabric is applied to the fabric.The mechanical properties,elasticity and electrical properties were tested and analyzed.The effects of weaving methods,yarn properties and composition on the tensile strength and elasticity of the fabric were explored,and the strain-resistance relationship of the fabric was further studied.The results show that the tensile strength,elasticity and electrical properties of the SS/C elastic fabric are affected by the yarn's strength,elasticity,electrical properties and fabric structure.Under the same yarn count and density conditions,when the stainless steel content is 20% and 30%,respectively,the elastic yarn fabric composed of SS/C ammonia-coated yarn and spandex has the same tensile strength and elastic properties.The double-elastic fabric has a higher strength than the weft elastic fabric,and the double-elastic fabric has a small latitudinal plastic deformation rate.During the stretching process,the electrical resistance of the double-elastic fabric warp yarn is higher than that of the weft elastic fabric because it affects the contact between the stainless steel staple fibers.The strain-resistance change state of the fabric is divided into two types,one is that the resistance decreases gradually with the tensile volume;the other is that the tensile volume resistance increases first and then decreases.Fabric strain-volume resistance is affected by two aspects,one is the change of the degree of electrical contact between the SS/C conductive yarns;the other is the close contact between the stainless steel fibers in the yarn after the SS/C conductive yarn is stressed.degree.(3)Study on electromagnetic shielding effectiveness of elastic electromagnetic shielding fabricThrough the analysis of the mechanical,elastic and electrical properties of the SS/C ammoniacoated elastic conductive yarn and the elastic conductive fabric composed thereof,the elastic characteristics and strain-resistance characteristics of the yarn and the fabric are clarified.Among them,the resistance of the yarn changes during the stretching process;the bulk resistance of the fabric also changes with the strain.These studies have important guiding significance for the development of electromagnetic shielding elastic fabrics,but they also need to be verified by SE research of elastic shielding fabrics.In this chapter,the strain-SE of the fabric is tested by the shielded chamber method,and the trend of the elastic fabric with the tensile SE and the factors affecting the SE are determined.The results show that after ironing,the wrinkles on the surface of the fabric are reduced,and the scattering of electromagnetic waves is reduced,resulting in a decrease in SE.For different fabrics,SE is affected by many factors,and it is not possible to judge SE by only the change of surface wrinkles.Variety.The SE of the elastic stainless steel/cotton electromagnetic shielding fabric is affected by the elastic size,especially the presence of the spandex yarn in the yarn,which affects the contact between the stainless steel staple fibers and increases the resistance of the yarn,resulting in the SE of the weft elastic fabric being superior to the double Stretch fabric.Under the condition of electromagnetic wave vertical polarization test,the strain-SE of elastic stainless steel/cotton electromagnetic shielding fabric is divided into two cases: one is that the SE is basically consistent before and after stretching,and the other is that the tensile SE decreases;and when the electromagnetic wave horizontal polarization test At the same time,the SE of the weft elastic fabric increases as the SE is stretched.Similarly,the silver-plated fiber/ammonia-spun fabric strain-SE also has the aforementioned three cases. |
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