The first stage
Surface treatment stage of fiber or fabric with hygroscopic antistatic agent.
Water has a very high electrical conductivity. As long as a small amount of water is absorbed, the conductivity of the polymer can be significantly improved. Water can provide a transfer medium for electric charges and promote the movement of ions to the opposite electrode, and when water decreases, it can be replenished from the atmosphere. Using this characteristic of water, a series of antistatic agents have been developed. Antistatic agents are surfactants with hydrophilic and hydrophobic groups. The hydrophobic group points to the surface of the fiber material, adsorbs on the phase interface, and changes the state of the phase interface; the hydrophilic group points to the space, adsorbing moisture in the atmosphere.
Antistatic agents generally have these kinds of effects on the surface of fibers and their products:
1. Hygroscopic effect: a continuous monomolecular water film is formed on the surface of the fiber material.
2. The effect of reducing specific resistance: The water film on the surface of the fiber material improves the dielectric coefficient of the fiber material, thereby effectively reducing the surface specific resistance.
3. Enhance ion conductivity: increase the ion concentration on the surface of the fiber material, and enhance the conductivity of ions (including protons) in water vapor.
4. Promote the dissolution of electrolyte: provide a place for the dissolution of carbon dioxide in the air and the electrolyte present in the fiber material.
5. Electrical neutralization: When the charge sign of the antistatic agent is opposite to that of the fiber material, electrical neutralization will occur.
Advantages: convenient processing, low cost, and obvious antistatic effect.
Disadvantages: The antistatic performance is very dependent on the environmental humidity. When the humidity is low (RH<40%), the antistatic performance is lost and the durability is poor.
second stage
Add antistatic agent inside the fiber to modify the fiber.
An antistatic agent component is added inside the basic polymer, blended or copolymerized with the basic polymer, and a composite spinning method is used to make a sea-island or skin-core composite antistatic fiber. The island phase or core is a polymer containing an antistatic agent, and the basic polymer as the marine phase or skin is the main body of the fiber, which protects the hydrophilic group of the polymer and assumes the basic function of the fiber . Antistatic agents inside antistatic fibers are mostly polar or ionic surfactants. Its molecular structure also has hydrophilic groups and hydrophobic groups. Hydrophobic groups have certain compatibility with basic polymers, while hydrophilic groups make them hygroscopic.
Antistatic mechanism of antistatic fiber: The hydrophilic group contained in the antistatic agent inside the fiber can migrate to the surface layer of the fiber and form a water film. The water film absorbs water vapor in the atmosphere to improve the dielectric of the fiber Function, reduce the surface specific resistance of the fiber, and accelerate the leakage of net electrostatic charge.
Advantages: Because the antistatic agent is inside the basic polymer, its durability is better.
Disadvantages: The function of antistatic agent depends on its hygroscopicity, which is destined to depend on the environmental humidity. Under low humidity (RH<40%), the antistatic performance will be lost. Large amount.
The third stage
Metal fiber and conductive material surface coating stage.
1. Metal conductive fiber: The conductive fiber is made by using the excellent conductive properties of metal, making it the earliest and true conductive fiber. Its resistivity can reach 10¯²～10¯¹ Ω · cm. Commonly used metals for metal fibers are: stainless steel, copper, aluminum, nickel, gold, silver, etc. At present, the most widely used are 304, 304L and 316, 316L stainless steel fibers. The main production method is the direct stretching method. The metal wire rod is repeatedly stretched through the die to produce fibers with a diameter of 4 to 10 μm (currently the thinnest has reached less than 1 μm), with a breaking strength of 5 to 15 cN/dtex and a breaking elongation of 3.0 to 5.0%. Stainless steel fiber has excellent durability, thermal conductivity, bending resistance, wear resistance, and radiation protection. When the metal fiber content is greater than 0.5%, the fabric has certain antistatic properties. When the metal fiber content is 2 to 5%, the fabric has good antistatic properties. When the metal fiber content is greater than 8%, the fabric not only has antistatic properties, but also has certain electromagnetic wave shielding properties.
Metal fiber content and antistatic properties
Note: The electrical conductivity of stainless steel fiber increases with the increase of fineness, when the fineness is less than 8μm, it decreases with the increase of fineness. Disadvantages: the fiber is stiff, the cohesion is slightly worse, the dyeability is poor, and the fiber price is higher.
2. Conductive fiber coated on the surface of conductive material:
This fiber is represented by the carbon black surface-coated conductive fiber first developed by the German BASF company in the 1960s. The production method is to coat and fix metal, carbon, conductive polymer and other conductive substances on the surface of ordinary fibers through physical and chemical methods. The conductive components of this fiber are distributed on the surface of the fiber, so the antistatic effect is good, but in the process of use, the conductive substance is easy to fall off, so that the conductive performance is lost.
The fourth stage
Composite conductive fiber stage.
In 1975, DuPont used composite spinning technology to make composite conductive fiber containing carbon black conductive core-Antron (Antron III). As a result, major chemical fiber companies have begun research and development of composite fibers that use carbon black as a conductive component. Monsanto has developed side-by-side conductive fibers, Japan Bell Textile has developed nylon conductive fibers, Unijica, Kuraray and Toyobo have successively developed composite conductive fibers. During this period, the carbon black composite conductive fiber has been greatly developed. By the end of the 1980s, Japan's annual output reached 200 tons. Because carbon black composite conductive fiber uses carbon black as the conductive component, the fiber is usually black gray, which limits the scope of application.
The appearance of carbon black composite conductive fibers has promoted the development and production of inlaid antistatic fabrics.
The fifth stage
The development stage of the whitening of conductive fibers.
In the 1980s, the whitening research of conductive fibers was started. A common method is to use sulfides, iodides or oxides of metals such as copper, silver, nickel and cadmium to blend or composite spin with ordinary polymers to make conductive fibers. For example, the conductive fiber made of CuS conductive layer by chemical reaction; the conductive fiber T-25 made by Teijin Company and containing CuI; the conductive fiber containing Zn0 made by Zhongfang Company; the companies such as Unijka also made white Conductive fiber. The performance of white conductive fibers that use metal compounds or oxides as conductive materials is not as good as carbon black composite conductive fibers, but their application is not limited by color.
Sixth stage
R&D stage of polymer conductive fiber
The polymer conductive fiber is an intrinsic polymer conductive fiber made by doping a polymer material. Such as polypyrrole, polythiophene, polyaniline and other polymer materials. These intrinsic conductive polymers have high conductivity (up to 10¯³~10¯²s/cm).
Some encouraging progress has been made in the research of such materials. But there are still some difficulties in practical application, mainly due to poor processing performance. In addition, research on superconductivity of polymers at home and abroad is also in progress. Research on the intelligent textiles of electronic information is also in progress.
Domestic research and development of conductive fibers is relatively late. In the 1980s, domestic production of metal fiber and carbon fiber began, but the output was small. Most of the required conductive fibers are imported. The earliest domestic research and development of metal fibers are scientific research institutions such as Lanzhou Institute of Mining and Metallurgy and some enterprises, such as the 540 factory in Xinxiang. The domestic research and development of carbon black composite conductive fibers include Wuxi Textile Research Institute and China Textile Yousi of the Academy of Textile Sciences. The current technology is relatively mature. There are also quite a few domestic universities, scientific research institutions and some large enterprises that have successfully developed a variety of organic conductive fibers and white conductive fibers.
Such as: copper-plated, nickel-plated metal polyester conductive fiber, copper iodide conductive acrylic fiber, conductive fiber made of copper iodide polyester blended yarn, carbon black composite fiber, etc. In terms of the production technology of white conductive fibers, domestic companies have successfully developed island-type fiber technology and so on. In general, there is still a certain gap with the advanced foreign level, such as product quality and stability.
