The Research And Development Of Non-woven Fabric For Electromagnetic Shielding

Electromagnetic shielding fabrics because of their easy to use,light weigh,low price and easy production features gradually become a hot research at home and abroad in recent years. At present,the most common electromagnetic shielding fabrics are woven fabrics and knit fabrics. The researches on electromagnetic shielding nonwovens are very little. In this paper,the electromagnetic shielding nonwovens with carbon fibers、stainless steel fibers and polyester fibers which are produced by the non-woven techniques are studied. This kind of nonwovens are used as tents in the military field 、industrial field and the civilian field. It has very good economy value and practicality.There are two mainly facts in this paper.First of all, The stainless steel fibers whose length is 35~45 mm and fineness is 8μm,the carbon fibers whose length is 40~45mm and fineness is 9μm and the polyester fibers whose length is 55 mm and fineness is 3D are equably mixed together with some inverse proportion. Then the bats are produced trough roller carding and cross laving. In order to enhance the mechanics capability,the bats must be bonded. The consolidation is needle punching. On this basis,electromagnetic shielding performance, the weight per square meter, thickness, air permeability and mechanical properties are tested. Then according to the electromagnetic shielding performance, five samples are chosen from all nonwoven fabrics. The best comprehensive properties of electromagnetic shielding nonwoven are determined by fuzzy comprehensive evaluation. The experimental results show that the best combinations of the parameters is stainless steel fibers content at about 35 percent, 2mm in the thickness, needle density of 300 thorn/cm2, pre-needling depth of 9mm, the main and inverted needling depth of 7mm.Second, in order to improve the electromagnetic shielding performance of the nonwovens, the nonwovens, which were made by the best combinations of the parameters, will be given a coating finishing. The coating finishing uses orthogonal experiment, with four factors and three levels, to determine the optimal coating finishing process. The experimental results show that the optimal coating finishing process is copper powder of 70 percent, coupling agent of 2 percent, the drying temperature of 100℃and the drying time of 15 min. Finally, the performance of the coated fabrics are compared with the uncoated fabrics. The results show that after the coating finishing, the thickness、the weight per square meter and mechanical properties of the nonwovens are increased. But the elongation at break and air permeability are declined. At the frequency of 2450 MHz to 2450 MHz, the electromagnetic shielding performance of the fabric, after the coating reaches 36.30 d B, the final nonwoven sample has good electromagnetic shielding properties.