Knowledge of anti-electromagnetic radiation textiles

- Apr 11, 2020-

After the intensity of electromagnetic radiation exceeds the exposure limit, electromagnetic waves will cause harm to human bodies and interfere with electronic and electrical equipment. Electromagnetic shielding fabric is an excellent shielding material with both light weight, flexibility and strength. At the same time, it has the characteristics of controllable structure, flexible weaving, gentle washing and other characteristics; besides being used in industry, it also has good taking performance and can be prepared into electromagnetic Radiation protective clothing protects workers who work in environments that exceed electromagnetic radiation exposure limits and reduces the occupational risks of employees.

The conductive materials used for electromagnetic shielding fabrics are mainly two types of metals and intrinsic conductive polymers. Commonly used conductive fiber or metal functional layers are stainless steel, silver, copper, nickel, aluminum, etc. Intrinsically conductive polymers (ICP) such as PANi, PPy, and PTh coated fibers have poor bonding fastness and are prone to wear during weaving, so more research has focused on conductive polymer coated fabrics. Although ICP-coated fabrics or fibers have lower resistivity and certain shielding effectiveness, they have certain advantages in other types of electromagnetic compatibility or shielding products, but whether it is fibers or fabrics, there are the following problems: ICP has color, Such as PANi is green and PTh is light blue, etc., which will affect its application; whether it is chemical polymerization or electrochemical polymerization, there is a problem of equipment corrosion; washing resistance is poor; compared with metalized fabrics, the processing cost is higher. Therefore, the electromagnetic shielding fabrics, especially the wearing fabrics, are rarely used. The widely used shielding fabrics are still cost-effective stainless steel fiber fabrics and metalized fabrics plated with copper, nickel, silver and other metals.

Electromagnetic shielding fabric woven with metal fiber blended yarn is an effective method for shielding electromagnetic waves. At present, the metal wires contained in the electromagnetic wave shielding fabric are mainly stainless steel fibers and nickel fibers, and the fiber diameter is about 4 to 10 μm. The content of the metal wire is 20% to 30%, but due to the metal fiber's hard hand, large friction coefficient, high density, strong rigidity, fiber toughness, curling, poor elasticity, poor cohesion and other problems, it is generally suitable for ordinary fibers Blending, but the spinnability is much more difficult than ordinary fibers, we must further explore the production process, improve spinning quality, increase production efficiency and yield.

In terms of metallized fibers and fabrics, the electroless plating process is used to produce electromagnetic shielding fabrics, which have high conductivity and mainly use reflection loss for electromagnetic waves. However, when using chemical plating methods, the fabrics must be desized and degreased. Then, roughening, sensitization and activation pretreatment are required; using silver-based composite plating technology, that is, the pure natural fabric yarn is first subjected to vacuum sputtering silver plating, and then subjected to one-bath composite gold plating. The new generation of radiation protection clothing has super strong electromagnetic wave reflection performance and excellent silver mirror effect. It can meet the needs of a variety of complex electromagnetic environments from 300MHz to 300GHz. The shielding effectiveness after washing is also suitable for complex environments such as acids, alkalis and salts. The multi-layer composite structure anti-electromagnetic wave protective clothing developed by Tiannuo Optoelectronics Co., Ltd. The surface layer is a double-layer structure interwoven with high-performance aramid (or polyimide) stock solution colored fibers and conductive silver fiber filaments, in which the conductive silver fibers are long The wire adopts electroless coating technology, shielding radio waves up to 60dB, the middle layer is compounded with PTFE film, and the inner layer is compounded with aramid (or polyimide) knitted fabric; The structure form is sewn together, minimizing the number of seams and interfaces; the neckline, cuffs and trousers are all designed with close fitting, and the seams are sewn with conductive filaments to ensure that the composite shielding fabrics in each part are between The electrical conductivity ensures a good anti-electromagnetic wave effect, and also has the functions of fire retardant, waterproof and moisture permeability.

In terms of functional nanofiber applications, the low cost of lightweight polyaniline (PANI) raw materials, the high conductivity of carbon nanotubes (conductivity of 104S / cm) and thermal stability (thermal conductivity of more than 200W / (m • k) ) Features are widely noticed by researchers. Harbin Institute of Technology in China and Lamar University in the United States collaborated on the research of PANI / PAN / MWCNT multi-component nanofibers. The electrospinning process was used. When the addition amount of MWCNT components is 3%, 5% or 7%, the electrical conductivity of PANI / PAN / MWCNT nanofibers is increased to 1.79, 3.26 or 7.97 S / m, respectively, and it has good electromagnetic wave adsorption performance.