An overview of static electricity in anti-static fabrics

Matter is composed of molecules, and molecules are composed of atoms. Atoms are composed of negatively charged electrons and positively charged protons. Under normal conditions, the number of protons in an atom is the same as the number of electrons, and the positive and negative balances, so it appears uncharged to the outside world. However, electrons surround the atomic nucleus and will break away from the orbit once external force is applied, leaving the original atom and invading other atoms B. Atom A has a positive charge due to the lack of electrons, which is called a cation. Atom B becomes positively charged due to the increase in the number of electrons. Negatively charged phenomena are called anions.

The cause of unbalanced electron distribution is that electrons are derailed by external force. This external force contains various energies (such as kinetic energy, potential energy, thermal energy, chemical energy, etc.). In daily life, any Static electricity can be generated when two objects of different materials come into contact and then separate.

When two different objects come into contact with each other, one object loses some charge, such as electrons are transferred to the other object, making it positively charged, while the other object gets some remaining electrons and becomes negatively charged. . If the charge is difficult to neutralize during the separation process, the charge will accumulate and the object will be charged with static electricity. Therefore, when objects come into contact with other objects and separate, they will be charged with static electricity. Usually when peeling off a plastic film from an object, it is a typical "contact separation" electrification. The static electricity generated by taking off clothes in daily life is also "contact separation" electrification.

Solids, liquids and even gases will become statically charged due to contact separation. This is because gases are also composed of molecules and atoms. When the air flows, molecules and atoms will also undergo "contact separation" and become electrified.

Static electricity on the human body is mainly caused by the friction between clothes or between clothes and the body. Therefore, the degree of "charge" when wearing clothes of different materials is different. For example, when wearing clothes made of chemical fibers, It is easier to generate static electricity, and cotton clothing generates less. And because a dry environment is more conducive to the transfer and accumulation of charges, people will feel that the static electricity on their bodies is relatively large in winter.

In dry and windy autumn, we often encounter this phenomenon in daily life: when taking off clothes to go to bed at night, crackling sounds are often heard in the dark, accompanied by blue light, shaking hands when meeting Sometimes, as soon as your fingers come into contact with each other, you will suddenly feel a stinging pain like a needle on your fingertips, which is shocking; when you get up in the morning and comb your hair, your hair will often "float" and become more and more messy. When you pull the door handle or turn on the faucet, Everyone will get an "electric shock" and often make a "pop, pop" sound. This is the static electricity that occurs in the human body. The above-mentioned phenomena are the result of the "discharge" of static electricity in the body to the outside.

When the human body moves, static electricity is generated by friction between skin and clothes and between clothes. As the number of household appliances increases and people wear more chemical fiber clothes in winter, the electrostatic charges generated by household appliances will be absorbed and accumulated by the human body. In addition, the walls and floors in the living room are mostly insulators and the air is dry, so they are more susceptible to electrostatic interference.

In a production environment without anti-static treatment, the relationship between the intensity of static electricity and humidity generated by the daily work of electronics factory personnel is shown in Table-1.

Table 1 shows the relationship between electrostatic intensity and humidity. Human activity conditions. Electrostatic voltage (V) 10~20RH 65~90RH. Walking through chemical fiber carpet 35000 1500. Taking TEFLON silicon wafer rack 30000 1200. Walking across plastic floor 12000 250 Sitting on a chair and working 6000 100 Looking at the plastic surface instruction document 7000 600 Picking up an ordinary polyethylene bag 20000 1000 Sitting on a polyurethane foam pad 18000 1500 As can be seen from Table 1, increasing the humidity of the working environment can reduce the electrostatic voltage. Any object is charged internally. Under normal conditions, the number of positive and negative charges is equal and does not appear to be charged to the outside. However, when two different objects come into contact or rub, one object has negatively charged electrons. It will cross the interface and enter another object, and static electricity will be generated.

And because the charges they carry accumulate, a high electrostatic voltage is generated. When two objects with different charges separate or come into contact, sparks appear. This is the phenomenon of electrostatic discharge. The main causes of static electricity include friction, piezoelectric effect, induction charging, adsorption charging, etc.

In industrial and agricultural production, static electricity plays a great role, such as electrostatic flocking, electrostatic spray painting, electrostatic insect removal, etc. At the same time, due to the existence of static electricity, some hazards are often caused, such as electrostatic discharge. fire accidents, etc. With the rapid development of the petrochemical industry, materials that easily generate static electricity are used more and more widely, and their fire hazards are also increasing.

Static electricity has many hazards. The first hazard comes from the interaction of charged objects. When the aircraft body rubs against air, water vapor, dust and other particles, the aircraft will be charged. If no measures are taken, it will seriously interfere with the normal operation of the aircraft's radio equipment and make the aircraft deaf and blind; in the printing factory, paper pages The static electricity between them will cause the paper pages to stick together and be difficult to separate, causing trouble for printing; in pharmaceutical factories. Because static electricity attracts dust, the medicine will not reach the standard purity; when the TV is played, the static electricity on the screen surface can easily absorb dust and oil, forming a film of dust, which will reduce the clarity and brightness of the image; just on blended clothes Dust that is common but difficult to dust off is also caused by static electricity. The second major hazard of static electricity is the possibility of explosions caused by static sparks igniting certain flammable objects. In the dark night, when we take off nylon and woolen clothes, sparks and "blah" sounds will be emitted, which are basically harmless to the human body. However, on the operating table, spark removal will cause an anesthetic explosion, injuring doctors and patients; in a coal mine, it will cause a gas explosion, resulting in the death and injury of workers and the scrapping of the mine.

The generation of static electricity is inevitable in industrial (related product) production, and the harm caused by it can be mainly attributed to the following two mechanisms: One: the harm caused by electrostatic discharge (ESD). (1) Cause malfunction or malfunction of electronic equipment and cause electromagnetic interference. (2) Breakdown of integrated circuits and precision electronic components, or aging of components, reducing production yield. (3) High-voltage electrostatic discharge causes electric shock and endangers personal safety. (4) It is easy to cause explosions and fires in production sites with a lot of flammable and explosive goods or dust and oil mist.

(1) Electronic industry (related products): adsorbs dust, causing pollution of integrated circuits and semiconductor components, greatly reducing the yield. (2) Film and plastic industry (related products): The film or film will be unevenly wound; the film and CD plastic tray will be contaminated with dust, affecting the quality.

The following are some specific hazards of static electricity in production:

1. When the static charge generated by an object accumulates and forms a high potential, when it comes into contact with other uncharged objects, a high potential difference will be formed and discharge will occur. When the voltage reaches more than 300 volts, the static sparks generated can ignite surrounding combustible gases and dust. In addition, static electricity also has certain hazards to industrial production and can also cause harm to the human body.

2. Solid materials will be subject to large-area friction and extrusion during transportation or production processes, such as friction between belts and pulleys in transmission devices; fixed materials contact polymerization or separation under pressure; solid materials During extrusion, filtration and piping. The filter is rubbing; solid matter is pulverizing. Static electricity can be generated during grinding and mixing processes and other similar processes. And as the speed increases. Increased pressure, and friction. The contact surface during extrusion is too large, the air is dry, and the equipment is not well grounded, etc., resulting in the accumulation of static charges and discharge, resulting in fire hazards.

3. Generally flammable liquids have a large resistance. During the filling, conveying, transporting or production processes, static electricity can be generated due to collision with each other, splashing, friction with the pipe wall, or impact. . Especially when there are no conductive particles in the liquid, the inner surface of the conveying pipe is rough, the liquid flow rate is too fast, etc., strong friction will occur. The generated electrostatic charge will accumulate voltage and cause discharge without a good static elimination device. May cause fire.

4. Dust moves at high speed during grinding, stirring, screening and other processes, causing collisions and friction between dust and dust, and between dust and pipe walls, container walls or other appliances and objects, thereby generating a large amount of static electricity. It will cause an explosion.

5. Compressed gases and liquefied gases, because they contain liquid or solid impurities, will generate a large amount of static electricity under strong friction when they are ejected from pipe openings or damaged areas at high speed, leading to combustion or explosion accidents.

6. Electric shock caused by static electricity may occur when the human body is close to electrostatically charged substances, or when the electrostatically charged human body is close to a grounded body. At this time, the static electricity charged by the human body can be as high as tens of thousands of volts. The severity of electrostatic shock is related to the energy stored in the electrostatically charged object. The greater the energy, the more severe the electric shock. The greater the capacitance or the higher the voltage of the electrostatically charged object, the more serious the electric shock will be. The electrostatic energy generated during the production process is very small, so the resulting electric shock will not be directly fatal. However, the human body may fall or fall due to electric shock, causing secondary accidents. In addition, electric shock can also cause mental stress among staff and affect their work.

7. Static electricity can hinder production or reduce product quality. In the textile industry, static electricity tangles fibers, absorbs dust, reduces the quality of textiles, and causes hazards such as fluttering threads, tangles, broken ends, and yarn tangles. ; In the printing industry, static electricity causes paper lines to be uneven and cannot be separated, affecting printing speed and printing quality; in the photosensitive film industry, electrostatic sparks make the film photosensitive and reduce film quality; in the powder processing industry, static electricity causes powder to be adsorbed to equipment It affects the filtration and transportation of powder; static electricity may also cause malfunction of electronic components; interfere with radio communications, etc.

In short, electrostatic hazards are caused by electricity and static sparks. The most serious electrostatic hazards, electrostatic discharge, cause fires and explosions of combustibles. It is often said that measures to nip problems in the bud and prevent the generation of static electricity are generally to reduce the flow rate and flow rate, modify process links that generate strong electricity, and use equipment and materials that generate less electricity. The simplest and most reliable way is to ground the device with a wire, which can lead the charge to the earth and avoid static electricity accumulation. Careful passengers will probably find that discharge brushes are installed on the wingtips on both sides of the aircraft and at the tail of the aircraft. When the aircraft lands, in order to prevent passengers from being shocked when flying off, most aircraft landing gears use special grounding tires or grounding wires; To discharge the static charge generated by the aircraft in the air. We often see an iron chain trailing from the rear of a tanker truck, which is the grounding wire of the vehicle. Appropriately increasing the humidity of the working environment allows charges to be released at any time, which can also effectively eliminate static electricity. This is why it is not easy to conduct static electricity tests in humid weather. The antistatic agent studied by scientific researchers can effectively eliminate static electricity inside the insulator.

Static electricity also poses certain dangers to the human body. According to medical experts, static electricity can cause certain harm to the human body. The electrostatic interference generated by the human body can change the normal potential difference on the human body surface, affecting the normal electrophysiological process of the myocardium and the normal conduction of cardiac electricity without interference. This kind of static electricity can aggravate the patient's condition or induce premature beats. Long-lasting static electricity can also increase the alkalinity of the blood, causing the calcium content in the serum to decrease and the excretion of calcium to increase, thereby causing skin itching and pigmentation, affecting people's health. It affects the physiological balance of the body, interferes with people's emotions, etc.

Many computer workers suffer from facial erythema, pigmentation and other facial diseases. The static electricity generated by the computer screen attracts a large amount of suspended dust, which causes facial irritation. In addition, because the skin of the elderly is relatively drier than that of young people, coupled with factors such as the aging of the cardiovascular system and weakened anti-interference ability, they are more susceptible to the harm of static electricity and cause cardiovascular diseases.

The air is too dry in winter, and static electricity is easily generated between human skin and clothing. The instantaneous static voltage can reach tens of thousands of volts, causing discomfort to the human body. Some people have conducted investigations and actual measurements on static electricity generated in daily life. Walking on carpet can generate 1,500 to 35,000 volts of static electricity, and walking on vinyl floors can generate 250 to 12,000 volts of static electricity. If your butt rubs against a chair indoors, it will Generates static electricity of more than 1800 volts. The level of static electricity mainly depends on the humidity of the surrounding air. Usually when static electricity exceeds 7,000 volts, people will feel an electric shock.

Relevant data shows that static electricity is very harmful to the human body. Long-lasting static electricity can increase the alkalinity in the blood, reduce the calcium content in the serum, and increase the excretion of calcium in the urine. This is especially true for growing children, the elderly with very low blood calcium levels, and people who need a lot of calcium. Pregnant women and nursing mothers are undoubtedly even worse off. Excessive accumulation of static electricity in the human body can also cause abnormal current conduction in brain nerve cell membranes, affecting the central nervous system, resulting in changes in blood pH and the body's oxygen characteristics, affecting the body's physiological balance, causing dizziness, headaches, irritability, and insomnia. , loss of appetite, confusion and other symptoms. Static electricity can also interfere with the human body's blood circulation, immunity and nervous system, affect the normal work of various organs (especially the heart), and may cause abnormal heart rate and premature heart beats. In winter, about one-third of cardiovascular diseases are related to static electricity. In flammable and explosive areas, static electricity on the human body can cause fires.

Static electricity has harmed all areas of people's production and life, such as military industry, pyrotechnics, petroleum, natural gas, chemical industry, shipping, photosensitive materials, coal mines, rubber, medicine, gas and other production; another example is Yuhang Fuel Tank storage sector, electronic device manufacturing, microelectronics related industries, mechanical electronics, optoelectronics, office automation, information communications, electronic medical, computer and other industries.

The hazards caused by static electricity have received considerable attention in the production departments of the chemical industry, but the research on the hazards and prevention of static electricity is still a weak link in the warehousing departments of these industries. With the continuous expansion of the functions and scale of warehousing, how to control and prevent the harm caused by static electricity has gradually attracted people's attention.

Static electricity is easily generated in the warehousing process. The generation of static electricity has its internal and external causes. The internal cause depends on the conductive properties of the material, and the most common external cause is the friction between materials causing electrification. Such as friction, rolling, impact, etc. between materials during storage and transportation. Followed by attached charging, induction charging, etc. As far as the warehousing department is concerned, many commodities and packages have internal conditions for the generation of static electricity. At the same time, warehousing operations are inseparable from operations such as handling, stacking, tarpaulin, and covering. Therefore, it is inevitable to generate static electricity between commodities. Friction, rolling, impact, etc. For example, when petroleum or organic solvents are transported in warehouses and discharged into tanks, friction will occur between these materials and pipeline walls and equipment, which will produce high static electricity accumulation. Plastic packaging of general commodities will also generate static electricity due to mutual friction during the stacking process.

Hazards of static electricity in warehousing. The harm caused by static electricity in warehousing activities is mainly due to the fact that it can accumulate on the surface of objects to form a high static potential and easily cause electrostatic discharge sparks. Its harm is mainly in two aspects:

It can easily cause explosions. ACCIDENT. For example, flammable liquids (such as gasoline, kerosene, diesel) and organic solvents (benzenes, ethers, ketones) stored in warehouses will explode if the vapor they volatilize mixes with air in a certain proportion, or the solid dust reaches a certain concentration. At the limit, once it encounters an electrostatic discharge spark, it will become an ignition source and cause explosion.

Easy to produce electric shock. For example, high-potential electrostatic discharges during transportation may cause discomfort to operators, which often occurs among workers who carry plastic packaging items in warehouses. High-potential electrostatic discharges may occur due to strong friction during transportation and stacking. , there have even been cases where operators were knocked down by electrostatic discharge.

In the process of storage, transportation, filling and adding of oil products, relative motions such as contact, friction and separation such as mixing, settling, filtration, shaking, impact, spraying, splashing and flow will inevitably occur. Static electricity builds up. During the flow of oil, the amount of static electricity depends not only on the generation of static electricity, but also on the dissipation of static electricity. When the rate of generation of static charges is higher than the rate of dissipation of static charges, accumulation of homogeneous charges is formed. The oil in the oil depot is a low conductivity substance. The resistivity of gasoline is 2.5*1013, and the resistivity of kerosene and diesel is 7.3*1014. Both of them are relatively easy to generate and accumulate static electricity.

The types of static electricity generated by oil products can be divided into three types according to their states: 1. Static electricity between oil products and solids, such as oil flowing and stirring in pipelines, and solid particles settling in the oil. The static electricity generated; 2. The static electricity between oil and gas, such as the static electricity generated by the oil sprayed from the pipe mouth or nozzle and the bubbles rising in the oil; 3. The static electricity between the oil and incompatible liquids, For example, static electricity generated by water droplets settling in oil products and high-pressure water flushing storage tanks.

It is divided into 6 types according to the form of mechanical movement: 1. Flowing electrification. Light oil with low conductivity flows in the pipeline, and friction occurs between the oil and the pipeline wall, causing the oil to have an electrostatic charge. 2. Jet charging. When oil is ejected from the nozzle or nozzle at high speed, there is a rapid contact and separation process between the particles and the nozzle. During the contact, a double electric layer is formed at the interface. During separation, the particles take away the charge of one layer of the double electric layer and the other layer. The layer of charge remains on the nozzle, resulting in positive and negative charges on the particles and the nozzle respectively. 3. Oil impact and splash are charged. Light oil is injected into storage tanks and tank trucks from the top opening. After the oil particles fall, they impact the tank wall, causing splashes, bubbles and mist droplets and becoming charged. 4. The liquid settles and becomes charged. Since the oil contains impurities such as solid particles and water, these particles or water droplets settle downwards and charge the oil. 5. The human body is charged. When the human body moves, the friction between clothes and clothes, the human body and clothes, the soles of shoes and the ground makes the human body electrified. 6. Induction charging. The charged body and the insulated conductor are brought close to each other so that the insulated conductor is charged.

The harm of static electricity is obvious to all, and now more and more manufacturers have begun to implement various degrees of anti-static (related products) measures and projects. However, it is necessary to realize that to improve and effective anti-static (related products) projects, corresponding countermeasures must be formulated according to the actual conditions of different enterprises and different working objects. Anti-static (related products) measures should be systematic and comprehensive, otherwise, it may achieve half the result with half the effort, or even cause destructive side effects. In every aspect of home and life, people have noticed the harm of static electricity to the human body.