electrostatic phenomenon

When the weather is dry, combing your hair with a plastic comb will attract your hair; When you take off your nylon clothes in the dark, you can not only hear the sound, but also see the sparks. These electrostatic phenomena caused by high-voltage static electricity generated by friction are a common natural phenomenon. Static electricity will bring trouble and harm to people. In the process of chemical fiber production and printing, the fluff and dust in the air are attracted by static electricity, which will reduce the product quality. The harm of static electricity is that electrostatic sparks will ignite flammable substances and cause explosions. Oil flows in the pipeline, coal is ejected from the pipeline mouth at high speed, air containing pulverized coal flows in the air duct, and gasoline is transported in the tank, all of which will generate static electricity due to friction. When static electricity accumulates to a considerable voltage; It will generate electrostatic sparks and cause explosions.

Electrostatic protection

How to prevent the harm caused by static electricity? The simplest and most reliable method is to ground the equipment with wires, so that the generated charge can be introduced into the earth in time. That's why we dragged a chain that touched the ground after seeing the tanker. Increasing air humidity is also an effective way to prevent static electricity. When the air humidity is high, the charge can be discharged at any time. This is the reason why the electrostatic experiment is difficult to succeed when the air humidity is high. Textile mills, detonators, explosives and other production workshops have strict requirements on air humidity, one of which is to prevent explosion caused by static electricity.

Chapter II: Electrostatic Application

The principle of electrostatic dust removal is shown in Figure 8. 19. B is a metal cylinder. A is the metal wire hanging in the center of the cylinder. The metal wire is connected to the negative high voltage terminal of several tens of kilovolts. Cylinder B is connected to the anode of high-voltage power supply and grounded. In this way, a strong electric field area is formed near the metal wire, which is enough to ionize the surrounding gas. These ionized gases meet the moving dust and make the dust charged. Under the action of electric field force, these charged dust will move to the electrodes (a, b). After reaching the electrode, it will gradually fall along the electrode. Therefore, the pollution of dust to the atmosphere can be reduced.

The principle of electrostatic spray painting, like electrostatic dust removal, is a new technology to spray paint by using electrostatic field formed by high voltage. Compared with manual painting, it has the advantages of high efficiency, less waste, good quality and being beneficial to workers' health. The picture shows the schematic diagram of the electrostatic spray painting device of the rotating cup. Paint enters the high-speed rotating metal cup B through the paint delivery pipe A, and the paint sprayed from the spray cup is atomized due to the high-speed rotation of the spray cup. Due to the negative high voltage (60- 120 kV) connected to the spray cup, the paint mist particles are negatively charged, which repel each other and disperse evenly. At the same time, under the action of electric field force, they fly to the workpiece C connected with positive high voltage, and are adsorbed on the working surface to form a bright and firm paint layer. Electrostatic spray painting will not pollute the air because of its small electric field force range. At present, electrostatic spraying has been widely used in the processing of mechanical parts, train carriages and so on.

Electrostatic flocking textiles often have all kinds of beautiful patterns, some of which are produced by electrostatic flocking. Fig. 8.2 1 is a schematic diagram of its processing process. The bottom is a metal mesh connected to the anode of high-voltage power supply, which is shaped like a disk and can store fluff. A strong electric field is formed between the metal plate and the metal mesh. The patterned textiles are drawn with adhesive in advance, placed on the metal plate, and driven by the reel to pass through the strong electric field. Due to the negative charge, the fluff in the metal mesh is repelled, falls through the metal mesh, and quickly falls on the textile under the action of electric field force, and part of it is stuck by adhesive. After the negative charge of the unbonded fluff is neutralized by the textile, it is repelled by the positive charge, and under the action of electric field force, it quickly returns to the metal net, thus forming beautiful patterns where the textile is stuck.

Static electricity is widely used in industry. In addition to the above examples, there are electrostatic photography. Electrostatic copying, as well as high-voltage live working and many other aspects. It is also widely used in modern scientific research, such as electrostatic accelerator.