Processing method for generating static electricity during production of plastic film

How does friction generate static electricity?

The film has little friction with the metal roll during production, so why does it generate static electricity? The principle of electricity tells us that strictly speaking, frictional electrification is only a form of contact and electrification. One of the main reasons for the generation of static electricity is that some of the electron clouds overlap when the two materials are in contact. When rapidly separated, one of the materials has the ability to adsorb electrons (or other charged particles, the same below), which may cause electrons to be transferred to the material, electrons to be negatively charged, and the other material to be positive. Electricity. In addition, in nature, there is piezoelectric (piezo) generated when a force is applied to an object and thermoelectricity generated when the object is heated, and triboelectric charging is a combined result of these effects.

Comparison of commonly used static eliminators.

Static eliminators are divided into passive and active types. The latter are divided into high-voltage power supply, ion wind type, and radio source type, because they need additional power supply, increase energy consumption, high-voltage power or Safety factors for radioactive sources are rarely used in plastic processing.

Plastic film production and application manufacturers used to use hard-type electrostatic brushes (anti-static brushes) in passive static eliminators. Nowadays, many manufacturers with high requirements have chosen some new static eliminators, such as soft-haired electrostatic brushes. .

Taking the electrostatic brush as an example, the elimination of the motor is mainly due to the electrostatic induction of the conductor, generating a positive charge opposite to the negative electrode of the film near the film, forming a corona current by air ionization, and generating a large amount of positive in the corona region. Negative ions. Under the action of the electric field, the negatively charged particles move toward the discharge needle B; the positively charged particles move toward the negatively charged film C, neutralizing the negative charge of the film strip. Since the electric field near the tip B depends on the potential of the film C itself and the distance from the tip to the film, the higher the voltage of the film C, the closer the distance from the tip B to the film C, and the higher the charge density induced on the tip B, The stronger the electric field formed nearby, the more the number of charged ions ionized, the better the static elimination effect (but it is easy to generate an arc when it is too close). It is conceivable that each bristles is like a lightning rod that extends into the air. It must be sharp and thin to better form the induced charge concentration, and discharge it one step earlier to achieve the purpose of eliminating static electricity. There are two main indicators to investigate the performance of this electrostatic cleaning brush: the threshold voltage and the corona current. The former is the lowest voltage that can cause the discharge needle to generate corona discharge, of course, the lower the better; the larger the latter, the more charge is eliminated per unit time. In practical applications, the resistance of the electrostatic brush can be tested with a multimeter. Generally, the electrostatic brush resistance of a good quality is less than 1 Ω/m. It can also be judged by using the ELD-1 static voltmeter to test the potential before and after the installation of the electrostatic brush. It is decided that there are many factors in addition to the performance of the electrostatic brush. The longer the discharge needle tip is, the better the conductivity of the material is, the better the performance of the electrostatic brush is.