When the intensity of electromagnetic radiation exceeds the exposure limit, electromagnetic wave will cause harm to human body and interference to electronic and electrical equipment. Electromagnetic shielding fabric is an excellent shielding material with light weight, flexibility and strength. At the same time, it has the characteristics of controllable structure, flexible knitting, soft and washable. 1n addition to being used in industry, it also has good wearing performance. 1t can be made into electromagnetic radiation protective clothing to protect workers working in the environment beyond the electromagnetic radiation exposure limit and reduce the occupational risk of employees
what factors affect the protective effect of electromagnetic protective clothing
electromagnetic radiation protective clothing is a shielding chamber made of shielding fabric, and its shielding effectiveness is jointly determined by the shielding effectiveness of the shielding fabric and the opening or gap structure of the chamber. The electromagnetic wave will enter the clothing through the neckline, hem or cuff opening, and the opening will leak electromagnetic wave
research shows that the opening structure of clothing significantly affects the shielding effectiveness. On the premise of high shielding effectiveness of protective fabric, more openings or gaps in protective clothing will eventually affect the shielding effect. Researchers found that when the polarization direction of the electric field is perpendicular to the slit, electromagnetic leakage is most likely to occur, and the wider the slit, the lower the protective effectiveness of the electromagnetic protective clothing. This is because the slit on the protective clothing cuts off the induced current, thus reducing the shielding effect on the electric field. When there are slits, the overall protection efficiency of protective clothing is difficult to reach more than 30dB. Some experts believe that the electromagnetic radiation protective clothing should be used in the professional workplace where the electromagnetic radiation exceeds the standard threshold, rather than the general daily work and living environment
design principles of electromagnetic radiation protective clothing
the following points should be considered in the design of electromagnetic radiation protective clothing
(1) in the design of protective clothing, the slit width that affects the protective effectiveness should be reduced as much as possible. On the premise of not affecting the comfort and efficacy of wearing, we should choose the appropriate clothing size as far as possible, moderately tight, and appropriately tighten the neckline, cuffs, trouser cuffs and the hem of the jacket; The possibility that the polarization direction of electric field is perpendicular to the slit should be minimized
(2) the slit should be properly treated to reduce electromagnetic leakage. 1f the protective material is covered in the slit position; For the shielding layer of adjacent parts, electrical connection shall be set to ensure the shielding effect
(3) for the electromagnetic radiation protective clothing with shielding effectiveness of more than 30dB, it is recommended to adopt the whole body closed structure, including hoods, gloves and shoes
(4) for the electromagnetic environment with low field strength and near-field radiation, and the field strength of the working environment is only slightly beyond the exposure limit, we can use the method of no cap, split type, or even only applying electromagnetic shielding materials to the local electromagnetic sensitive organs, so as to give consideration to the requirements of wearing comfort and ergonomics
What are the materials of electromagnetic radiation protective clothing
there are two kinds of conductive materials for electromagnetic shielding fabrics: metal and intrinsic conductive polymer. The commonly used conductive fibers or metal functional layers are stainless steel, silver, copper, nickel, aluminum, etc. The fibers coated with intrinsic conductive polymers (1CP), such as PAN1, PPy and PTH, have poor binding fastness and are easy to wear in weaving, so more research is focused on the conductive polymer coated fabrics
although 1CP coated fabric or fiber has low resistivity and certain shielding effectiveness, and has certain advantages in other types of EMC or shielding products, there are the following problems in both fiber and fabric: 1CP has color, such as PAN1 is green, PTH is light blue, which will affect its application; Whether chemical polymerization or electrochemical polymerization, there are equipment corrosion problems; The washing resistance is poor; Compared with metallized fabric, the processing cost is higher. Therefore, the widely used shielding fabrics are still stainless steel fabric with high cost performance and metallized fabric coated with copper, nickel, silver and other metals
relevant product standards and evaluation methods
the research and formulation of electromagnetic radiation standards in various countries mainly focus on the provisions of exposure limits and the shielding effectiveness test of simple shielding materials. GB / T 23463-2009 “protective clothing against microwave radiation” is the only product standard in China at present. The standard also gives the evaluation of Se grade of protective clothing, in which the shielding effectiveness of protection grade A is not less than 50 dB; The shielding effectiveness of protection grade B shall not be less than 30 dB; The shielding effectiveness of protection grade C is not less than 10 dB
protective clothing needs to be maintained after a period of use. For washable materials, D1N 32780-100 2002 stipulates that they should be washed 10 times; GB / T 23463-2009 stipulates that after 10 times of maintenance, the change of shielding effectiveness value of protective clothing shall be less than 5%, and the change of size shall not be more than 5% ± 3%, and the dimensional stability of fabric and functional layer is consistent; According to GB / T 33615-2017, the samples should be washed 10 times continuously according to GB / T 8629-2001 washing procedure 7a, and then tested for Washability shielding effectiveness after one drying procedure a