The first stage
Use hygroscopic antistatic agent to perform surface treatment stage on fiber or fabric.
Water has a 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 charge, promote the movement of ions to the opposite electrode, and when the water is reduced, it can be replenished from the atmosphere. Using this characteristic of water, a series of antistatic agents have been developed. The antistatic agent is a surfactant having a hydrophilic group and a hydrophobic group. 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 and absorbs water vapor in the atmosphere.
Antistatic agents generally have the following functions on the surface of fibers and their products:
1. Moisture absorption: a continuous monomolecular water film is formed on the surface of the fiber material.
2. Reducing specific resistance: The water film on the surface of the fiber material increases the dielectric coefficient of the fiber material, thereby effectively reducing its surface specific resistance.
3. Enhance ion conductivity: increase the ion concentration on the surface of the fiber material and enhance its ion (including proton) conductivity in water vapor.
4. Promote electrolyte dissolution: It provides a place for the dissolution of carbon dioxide in the air and electrolytes in fiber materials.
5. Electrical neutralization: When the charge sign of the antistatic agent is opposite to that of the fiber material, it will produce electrical neutralization.
Advantages: convenient processing, low cost, and obvious antistatic effect.
Disadvantages: The antistatic performance is very dependent on the environmental humidity. At low humidity (RH<40%), its antistatic performance is lost and its durability is poor.
second stage
Add antistatic agent inside the fiber to modify the fiber.
An antistatic agent component is added into the basic polymer, blended or copolymerized with the basic polymer, and a sea-island or sheath-core composite antistatic fiber is made by a composite spinning method. The island phase or core part is a polymer containing an antistatic agent, and the basic polymer as the sea phase or skin part is the main body of the fiber, which protects the hydrophilic group polymer and assumes the basic function of the fiber . The antistatic agent inside the antistatic fiber is mostly polar or ionic surfactant. Its molecular structure also has hydrophilic groups and hydrophobic groups. The hydrophobic group has a certain degree of compatibility with the basic polymer, while the hydrophilic group makes it have a certain degree of hygroscopicity.
Antistatic mechanism of antistatic fiber: The hydrophilic group contained in the antistatic agent inside the fiber can migrate to the surface of the fiber and form a water film. The water film absorbs atmospheric water vapor to increase the fiber's dielectric. Function to reduce the surface specific resistance of the fiber and accelerate the leakage of net electrostatic charge.
Advantages: Since the antistatic agent is inside the basic polymer, its durability is better.
Disadvantages: The effect of antistatic agent depends on its hygroscopicity, which is doomed to its dependence on environmental humidity. Under low humidity (RH<40%) conditions, it will lose its antistatic performance. The dosage is large.
The third stage
Metal fiber and conductive material surface coating stage.
1. Metal conductive fiber: The conductive fiber is made by using the excellent conductivity 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. The most widely used are 304, 304L and 316, 316L stainless steel fibers. The main production method is the direct drawing method. The metal wire is repeatedly stretched through the die to form a fiber with a diameter of 4-10μm (currently the thinnest is less than 1μm), the breaking strength is 5-15cN/dtex, and the breaking elongation is 3.0-5.0%. Stainless steel fiber has excellent durability, heat conductivity, bending resistance, abrasion resistance, and radiation resistance. When the metal fiber content is greater than 0.5%, the fabric has certain antistatic properties, and 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 anti-static property
Note: The electrical conductivity of stainless steel fiber increases with the increase in fineness. When the fineness is less than 8μm, it decreases with the increase in fineness. Disadvantages: the fiber is stiffer, the cohesive force is slightly worse, the dyeability is poor, and the fiber price is higher.
2. The surface of conductive material is coated with conductive fiber:
This fiber is represented by the carbon black surface-coated conductive fiber first developed by BASF in Germany in the 1960s. The production method is to coat and fix metal, carbon, conductive polymer and other conductive materials 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 material is easy to fall off and the conductive performance is lost.
Fourth stage
Composite conductive fiber stage.
In 1975, DuPont used composite spinning technology to make composite conductive fiber with carbon black conductive core-Antron III. As a result, major chemical fiber companies have begun to research and develop composite fibers with carbon black as the conductive component. Monsanto has developed side-by-side conductive fibers, Kanebo has developed nylon conductive fibers, and Unijika, Kuraray, and Toyobo have successively developed composite conductive fibers. During this period, the carbon black composite conductive fiber was greatly developed. By the end of the 1980s, Japan's annual output reached 200 tons. Because the carbon black composite conductive fiber uses carbon black as the conductive component, the fiber is usually dark gray, which limits the scope of application.
The emergence of carbon black composite conductive fibers promotes the development and production of inlaid antistatic fabrics.
Fifth stage
The whitening development stage of conductive fiber.
In the 1980s, research work on the whitening of conductive fibers was started. The common method is to use copper, silver, nickel and cadmium and other metal sulfides, iodides or oxides and ordinary polymers to blend or composite spinning to make conductive fibers. For example, the conductive fiber of the CuS conductive layer is made by chemical reaction; the conductive fiber T-25 containing CuI is made by Teijin Co., Ltd.; the conductive fiber containing Zn0 is made by Kanebo Co., Ltd.; Unijika and other companies have also made white Conductive fiber. The performance of white conductive fibers using metal compounds or oxides as conductive materials is not as good as that of carbon black composite conductive fibers, but its application is not limited by color.
Sixth stage
The development stage of polymer conductive fiber.
Polymer conductive fiber is an intrinsic polymer conductive fiber made by doping polymer materials. Such as polypyrrole, polythiophene, polyaniline and other polymer materials. These intrinsically conductive polymers have high conductivity (up to 10¯³~10¯²s/cm).
Research on this type of material has made some encouraging progress. However, there are still some difficulties in practical application, mainly due to poor processing performance. In addition, research on the superconductivity of polymers at home and abroad is also underway. Research work on the intelligent textiles of electronic information is also in progress.
Domestic research and development work on conductive fibers is relatively late. In the 1980s, domestic production of metal fiber and carbon fiber began, but the output was relatively small. Most of the conductive fibers needed depend on imports. The earliest domestic research and development of metal fibers are the Lanzhou Research Institute of Mining and Metallurgy and other scientific research institutions 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 Excellent Silk of Textile Academy. The current process technology is relatively mature. A considerable number of domestic universities and scientific research institutions and some large enterprises have also successfully developed a variety of organic conductive fibers and white conductive fibers.
Such as: metal polyester conductive fiber coated with copper and nickel on the surface, conductive acrylic fiber of copper iodide, conductive fiber made of copper iodide polyester blended spinning, carbon black composite fiber, etc. In the production technology of white conductive fiber, some domestic enterprises have successfully developed sea-island fiber technology and so on. Generally speaking, there is still a certain gap with foreign advanced level, such as in product quality and stability.
