As an important class of intelligent materials, conductive fibers have attracted widespread attention from the material circles at home and abroad. Its research and development are in the ascendant, and they have good application prospects in clothing, sensors and industrial textiles. It is believed that with the advancement of science and technology, smart materials will continue to develop. As one of the main varieties of smart textiles, conductive fibers will surely gain an increasingly important position in the field of materials.
Electroconductive fiber usually refers to a fiber whose specific resistance is below 107Ω·cm under standard conditions (20 ℃, 65% relative humidity). Categories are as follows: Pictures
(1) Metal compound type conductive fiber, the resistivity is 102～104Ω·cm, it is made by compound spinning method to mix high concentration conductive particles locally into the fiber, black conductive particles use carbon black, white series use metal oxide For example, the surface of antimony oxide containing a small amount of tin oxide is coated with titanium dioxide, the fiber is relatively light, flexible, washable and easy to process; it can also chemically fix the copper compound or electroplating metal through post-processing.
(2) Metal conductive fiber. This type of fiber is made using the conductive properties of metal. The main method is the direct drawing method, that is, the metal wire is repeatedly drawn through a die to make a fiber with a diameter of 4-16μm.
(3) Carbon black conductive fiber
Using the conductive properties of carbon black to make conductive fibers is an older and common method. The method can be divided into the following three categories: Picture
① Doping method: After mixing carbon black and fiber-forming material, the carbon black forms a continuous phase structure in the fiber, which gives the fiber conductivity. This method generally uses the sheath-core composite spinning method, which does not affect the original physical properties of the fiber, but also makes the fiber conductive.
② Coating method: The coating method is to coat carbon black on the surface of ordinary fibers. The coating method can use a binder to bond the carbon black to the fiber surface, or directly soften the fiber surface and bond it with the carbon black. The disadvantage of this method is that the carbon black is easy to fall off, the hand feel is not good, and the carbon black is not easy to be evenly distributed on the fiber surface.
③ Fiber carbonization treatment; some fibers, such as polyacrylonitrile fiber, cellulose fiber, pitch-based fiber, etc., after carbonization treatment, the main chain of the fiber is mainly carbon atoms, which makes the fiber conductive. The most common method is the low-temperature carbonization treatment method of acrylic fiber. image
(4) Conductive polymer fiber
Polymer materials are usually considered as insulators, but the successful development of polyacetylene conductive materials in the 1970s broke this
traditional mindset. After that, polymer conductive materials such as polyaniline, polypyrrole, and polythiophene were successively born. People conduct electricity to polymer materials.
Performance research has also become more extensive. There are two main methods for preparing conductive fibers using conductive polymers: (1) Direct spinning method of conductive polymer materials (2) Post-processing method.
Application of conductive fiber
Conductive fabrics made of conductive fibers have excellent functions such as electrical conductivity, heat conduction, shielding and absorption of electromagnetic waves, etc., and are widely used in conductive nets and conductive overalls in the electronics and power industries; electric clothing, electric heating surfaces, and electric heating bandages in the medical industry; aviation, Electromagnetic shielding cover for aerospace and precision electronics industries, etc. Conductive fibers can be used in fields such as antistatic textiles, anti-electromagnetic radiation textiles, smart textiles and military textiles.
Antistatic textiles
Conductive fiber is a functional fiber with electronic conduction as the mechanism, which eliminates static electricity through electronic conduction and corona discharge. Since the fiber contains free electrons, its antistatic properties are not dependent on humidity; Liheng conductive fiber has a short charge half-life, in any case, it can eliminate static electricity in a very short time, and use conductive fiber to prevent static electricity from generating and The hazard has a wide range of environmental adaptability. According to the conductivity of the conductive fiber and the structure of the fabric, the antistatic effect can be achieved by mixing 0.05% to 5% of the conductive fiber in the general fiber. Work clothes made of conductive fibers with antistatic effect, suitable for oil fields, petroleum processing, coal mines, electronics industry, photosensitive material industry and other flammable and explosive occasions, and also suitable for dust-free sterile clothing or special filter materials Wait.
Anti-electromagnetic radiation textiles
Electromagnetic shielding is the use of low-resistivity conductive materials to reflect and guide electromagnetic currents, and generate current and magnetic polarization opposite to the original magnetic field inside the conductive material, thereby reducing the radiation effect of the original electromagnetic field. Conductive fibers used as protection against electromagnetic radiation require very low resistivity, usually only 10-6 to 10-2Ω/cm. In recent years, due to the wide application of electronic and electrical equipment and communication equipment, the interference of electromagnetic radiation caused equipment misoperation, image and sound obstacles, and harm to the human body, etc., which aroused people's attention to the development of electromagnetic shielding materials. image
Using the electromagnetic shielding properties of conductive fibers, it can be used to make electromagnetic shields for precision electronic components, high-frequency welding machines, etc., to make walls and ceilings of houses with special requirements, and wall coverings that absorb radio waves. In Japan, conductive fibers coated with copper on the surface are blended or made into non-woven fabrics, which are now widely used as electromagnetic wave shielding and absorbing materials, such as electromagnetic wave absorbing covers for ships.
Textile sensor
The flexible conductive fiber is made of sensor textiles based on the principle of electronic sensors. It has the advantages of lightness and portability, and is widely used in various fields. Flexible wearable sensors are mainly dedicated to sensing and monitoring various human activities, and have a wide range of applications in motion sensing, personal health monitoring, intelligent robots and human-computer interaction. image
Traditional strain sensors, such as those based on metal foil and semiconductors, cannot be applied to flexible wearable sensors because they do not have good flexibility and have a small detectable range (<5%). Some nanomaterials have been applied to various flexible strain sensors, such as carbon nanotubes, graphene and metal nanowires, because of their good mechanical flexibility and electrical conductivity. Although some progress has been made, there are still two main problems today: one is that it is difficult to obtain high sensitivity and a large sensing range at the same time; the other is that the current flexible sensors have many functions and single functions, for example, they can only sense tensile strain. It cannot sense other deformations such as bending and torsion at the same time, so it is not suitable for sensing complex and delicate human activities. Japan Taiyo Industry Co., Ltd. uses carbon fiber to develop a sensor that detects the maximum strain, which can be used for safety diagnosis of structures such as buildings, roads, factories, airplanes, and ropeways.
Military textiles
The future war for military textiles will be an informationized war under high-tech conditions. In such wars, the pace of operations is fast, the frequency of offensive and defensive transitions is fast, and the war situation is changing rapidly, and traditional soldiers' combat equipment appears to be seriously backward. To improve the comprehensive combat capabilities of soldiers in the modern battlefield, it is necessary to improve the soldiers' ability to acquire, process, and transmit information, so that the soldiers' understanding of the battlefield situation can reach a higher level. Information clothing made of conductive fibers just meets this. One requirement. image
Most conductive fibers are sensitive to electricity and heat. The fabric woven from conductive fibers can prevent reconnaissance by thermal imaging equipment, and can be made into thermal imaging protective clothing for individual soldiers. Conductive fibers are compounded with low dielectric substrates such as resin and rubber to make electromagnetic wave absorbing materials, which can absorb radar waves, avoid radar tracking, and achieve the purpose of stealth weapons and equipment. The color-changing military uniform developed by the United States is to add a conductive circuit composed of conductive fibers to the fabric. By controlling the temperature, the thermochromic ink in the military uniform is changed, so that the color of the military uniform changes according to the color of the external environment. An environmentally reactive camouflage.
Other conductive fiber uses
Other applications By selecting functional conductive additives, fiber materials with other functions besides the conductive function can also be prepared, such as antibacterial and far infrared. Japan's Mitsubishi Corporation uses composite spinning technology to mix high-concentration white conductive ceramic particles in the core to make the fiber conductive. At the same time, because the added ceramic particles have the characteristics of light-to-heat conversion, after blending this fiber with conventional fibers in an amount of 10%, the temperature of the fabric can be raised to 28°C under the light source. This fiber not only makes the wearer feel warm, but after washing with water, its drying time in the sun is 2/3 of that of the conventional fiber. The quick-drying property is an additional characteristic of this fiber. Since the conductive particles of this fiber are in the core of the fiber, the usual processing, washing, dyeing, etc. will not affect the conductivity of the fiber.
