Textile materials
Textile materials are electrical insulator materials, with high specific resistance, especially synthetic fibers such as polyester, acrylic fiber, and chloro fiber. Therefore, in the process of textile processing, due to the close contact and friction between fiber and fiber or between fiber and machine parts. It causes the transfer of electric charge on the surface of the object, resulting in static electricity. The fibers with the same charge repel each other, and the fibers with different charges attract the parts. As a result, the sliver is hairy, the yarn hairiness is increased, the roll forming is not good, the fiber sticks to the parts, the yarn breakage is increased, and the dispersive strip shadow is formed on the cloth surface. After the clothing is electrified, a large amount of dust will be absorbed, which is easy to contaminate. Moreover, clothing and human body, clothing and clothing will also be entangled or generate electric sparks. Therefore, electrostatic interference affects the smooth processing, the quality of products and the wearing properties of fabrics. When the static electricity is serious, the static voltage is as high as several thousand volts, which will produce sparks due to discharge, cause fire and cause serious consequences.
It has been found for a long time that when two insulators rub against each other and separate, the higher dielectric coefficient objects have positive charge, and the lower dielectric coefficient objects have negative charge. This is a law discovered at the end of the 19th century, which is consistent with many experimental results,. The electrostatic potential sequence of various fibers obtained from the experiment is shown in table 3-32 (the experimental conditions are temperature and air relative humidity of 33%). When the two kinds of fibers in the table are in friction, the fibers on the top of the table are positively charged and the points below are negatively charged.
Table 1 fiber electrostatic potential sequence
Wool, nylon, viscose, cotton, silk, polyester, polyvinyl alcohol, polyacrylonitrile, chlorine, nitrile, chlorine, vinylpolypropylene, fluorine, fiber
+ -
The first potential sequence table in 1757, containing only wool as a textile material, is arranged at the near positive end of the table. Many people have done research in this field in the future. In some published potential sequences, the arrangement order of various fibers is not exactly the same, and some differences are relatively large. But generally speaking, polyamide fibers (wool, silk and nylon) are arranged near the positive charge end of the surface, cellulose fibers are arranged in the middle of the surface, and carbon chain fibers are arranged at the negative charge end of the surface. It should be noted that the slight change of experimental conditions may cause the change of fiber potential. And after the textile material is charged, the potential of each part of the material is not the same, some parts have positive charge, some parts may have negative charge, the situation is more complex.
The "strength" of static electricity carried by textile materials is expressed by the charged amount (Coulomb or electrostatic unit) of materials per unit weight (or per unit area). The maximum electric charge of all kinds of fibers is nearly equal, but the electrostatic decay rate is quite different. The main factor determining the rate of electrostatic decay is the surface specific resistance of the material. The relationship between the surface specific resistance of some fabrics and the half time required for electrostatic decay to half of the original value.
The logarithmic relationship between the charge half-life of various fabrics and the surface resistance is a linear relationship. The larger the surface specific resistance is, the longer the half-life is. Table 1 shows the relationship between the surface specific resistance of some fabrics and the charge half-life (test conditions are temperature 30oC and air relative humidity 33%). When friction occurs between the two fibers in the table, the fibers arranged on the surface are positively charged and the fibers below are negatively charged.
The "strength" of static electricity carried by textile materials is expressed by the charged amount (Coulomb or electrostatic unit) of materials per unit weight (or per unit area). The maximum charge of all kinds of fibers is nearly equal, but the decay rate of static electricity is very different. The main factor determining the rate of electrostatic decay is the surface specific resistance of the material.
The larger the surface specific resistance of the fabric, the longer the half-life of the charge. Therefore, if the specific resistance of textile fabric is reduced to a certain extent, electrostatic phenomenon can be prevented.
The production practice shows that the processing of cellulose fiber in textile mill is seldom disturbed by static electricity. Processing such as wool and silk, there is a certain electrostatic interference. However, the processing of polyester, nylon, polyester and other synthetic fibers is subject to the greatest electrostatic interference.
In order to solve the electrostatic interference in the wearing process of synthetic fiber fabric, it is necessary to make the synthetic fiber and its fabric have the durability and antistatic performance. There are many ways to make synthetic fibers and their fabrics have durable antistatic properties. For example, when the synthetic fiber is polymerized or spun, a hydrophilic polymer or a conductive low molecular polymer is added; or a composite fiber with hydrophilic outer layer is made by the composite spinning method. For example, in the process of spinning, the synthetic fiber can be blended with the fiber with strong moisture absorption, or according to the potential sequence, the fiber with positive charge can be blended with the fiber with negative charge, and the fabric can be treated with durable hydrophilic auxiliary.
There are three kinds of Antistatic Fabrics in the market: antistatic fabric with conductive wire, antistatic fabric with conductive fiber and antistatic fabric with auxiliary finishing.
