In the textile production process, static electricity will affect the quality of spinning and weaving products, and even affect the dyeing and finishing process. For example, after drying, the moisture content of fabric decreases, and it is not easy to generate static electricity. It is often adsorbed on metal parts, and there is a disorder winding phenomenon. Because the same fabric has the same charge and mutual exclusion, the falling cloth is not easy to fold and neatly, which affects the processing of the lower track. The operator's hand and the contact with the charged dry cloth are often subjected to electric shocks. The clothing with static electricity is easy to absorb dust and pollute. After taking the clothes with static electricity, they will be entangled with each other, and the phenomenon of "skirt embracing legs" will cause mutual discomfort.
Long time electrostatic interference can increase the blood sugar level of human body, and decrease the content of calcium and vitamin C in blood. It causes people to suffer from adverse reactions such as dryness, headache, chest tightness, cough and even lead to bronchial asthma and arrhythmia. Therefore, antistatic finishing of textiles is very important.
1. The causes of static electricity on textiles.
Electrostatic (electrification) is the excitation energy of electrons or ions occurring on the surface after the friction between the two substances and the surface of the contact occurs. The main causes of electrostatic generation are contact electrification, friction power generation, deformation electrification, photoelectric and thermoelectric effects.
The main reason for the electrostatic generation of textiles is the friction between textile materials. Most of the textile materials are poor conductors, which are higher than the resistance. In the process of production and processing, there will inevitably be friction, drafting, compression, peeling, electric field induction and hot air drying.
Two. Factors affecting the electrostatic properties of textiles
There are many factors that affect the static electricity of textiles, but mainly depend on the hygroscopicity and relative humidity and friction conditions of textiles.
(1) hydrophilic properties of textiles
The better the hydrophilicity of the fiber, the more moisture absorption, the lower the charged volume, the better the antistatic effect. It is easy to form surface water film or water pulse in the fiber surface and micro capillary, which is conducive to the discharge of electrons or ions. Natural fibers such as cotton, wool, silk and hemp are hygroscopicity, low resistance, static electricity phenomenon is not serious, and synthetic fiber is easy to generate static electricity due to its low moisture absorption and high crystallinity.
(2) relative humidity of air
The lower the relative humidity of the air is, the lower the moisture absorption rate of the fiber is. Even if it is hydrophilic fiber, it is easy to generate static electricity due to low moisture regain. Because even hydrophilic fibers are insulators under absolutely dry conditions.
(3) friction conditions
The more rough the fiber surface, the greater the friction coefficient, the more contact points, the more likely to generate static electricity. Two the faster the relative friction speed is, the greater the probability of point contact. The greater the charge density, the higher the potential difference. When friction occurs, the greater the pressure between fibers, the larger the friction area and the greater the amount of electric charge.
(4) air temperature
Temperature also has an effect on the static electricity of the fiber material. When the temperature rises, the resistance decreases and the charged quantity decreases. But the effect of temperature on static electricity is much smaller than that of relative humidity.
Three. Main methods of textile antistatic
The general electrostatic phenomenon is caused by the complex interlace between charge generation process (charge shifting, separation) and disappearance process (corona discharge and electrostatic leakage). When these two opposite processes reach equilibrium, the actual level of electrostatic charge.
The antistatic mechanism and methods of textiles can be summarized as follows: reducing the generation of charges, accelerating the leakage of electric charges and neutralizing static charges. The causes of static electricity, the mechanism and influence factors of textile antistatic, the main methods of textile antistatic are as follows:
(1) adding antistatic agent in finishing process of yarn or fabric.
This method is applicable to all kinds of fiber materials. After impregnation, impregnation and baking, the antistatic agent adheres or crosslinks on fibers or fabrics. The mechanism is to reduce the friction coefficient between fibers, improve the hygroscopicity of fibers, or ionize the surface of fibers, thereby inhibiting or reducing the generation of electrostatic charges and achieving the purpose of antistatic.
The antistatic agents used are divided into cationic, anionic and nonionic types. The cationic antistatic effect is the best, the anionic type is the best, and the non-ionic type is the most widely used.
The advantages of this method are: simple and easy to operate, low cost, especially suitable for eliminating electrostatic interference in textile processing, and the treated fabrics also have the functions of moisture absorption, antifouling and no dust absorption.
Disadvantages are: the durability of antistatic effect is poor, the surface active agent is volatile, and it is more resistant to washing. Moreover, it has poor antistatic effect in low humidity environment.
(2) blending, copolymerization, or grafting modification of fiber forming polymers.
Most of the synthetic fibers have poor conductivity and can add hydrophilic monomers or polymers into fiber forming polymers, which can improve the hygroscopicity and make the fibers antistatic. The mechanism and advantages and disadvantages are the same as those of fabric surface treatment.
(2) polymerization of hydrophilic polar monomers onto the backbone of hydrophobic synthetic fibers by copolymerization or graft polymerization. For example, embedding polyethylene glycol into PET macromolecules can also improve the hygroscopicity and antistatic properties of the fibers.
This method can make the fibers and fabrics better retain their original style and mechanical properties, and also have water washable and durable antistatic properties. However, they have poor alkali resistance and high cost, and antistatic agents are prone to problems when mixed with other auxiliaries.
(3) blended or embedded antistatic yarns.
Mixing a small amount of conductive short fibers into spinning can produce antistatic yarns, and at the same time reduce or even eliminate the electrostatic problems in spinning process.
Conductive fiber includes metal fiber (stainless steel fiber, copper fiber, aluminum fiber, etc.), carbon fiber and organic conductive fiber. At present, organic conductive fiber is used to develop antistatic blended yarn on the market.
The advantages of the method are: good washing resistance, friction resistance, heat resistance, light resistance and permanent antistatic property, and are not affected by the change of ambient temperature and humidity, and are being developed and applied more and more widely.
The disadvantages are: the price of conductive fibers is higher, the cost of making fabrics is higher, and most conductive fibers are dark. Therefore, when using conductive fibers to develop Antistatic Fabrics, we must pay attention to the dyeing properties of fabrics.
(4) coating method
The conductive material, such as graphite, copper powder or silver powder, is mixed into the coating to coat the surface of the fabric.
The fabric with nano sol and nano titanium dioxide has good antistatic effect, but washable. The newly developed nano conductive powder indium doped two tin oxide (ITO) is coated on the fabric with excellent electrical conductivity and transparency, and is free from climate and environmental limitations. It has long performance and simple method, and its drawback is poor air permeability.
Metal plating on the fabric surface (such as copper, nickel, silver, etc.) or composite plating (such as copper nickel plating) is also an effective antistatic method. The composite plating method has the characteristics of composite gold, retaining the advantages of plating single metal, and avoiding its shortcomings. Besides, it has the advantages of simple equipment, less investment, easy operation, soft fabric, good wearability, good popularization and good prospects.
With the improvement of clothing performance requirements and the consideration of precision and safety in production, the demand for antistatic textiles is getting higher and higher.
At present, the antistatic finishing of textiles has achieved some success. However, there are some shortcomings in these processes. Although the fabric has antistatic properties, it may cause the handle, whiteness and permeability of the finished fabric to drop to a certain extent, which affects the comfort performance of the fabric, and at the same time, it has the disadvantage that the antistatic property is not durable. Therefore, improving the antistatic properties of textiles is still an important research topic in the field of textile dyeing and finishing.