Comment on textile atmospheric pressure glow discharge plasma treatment technology

Plasma generation and application Plasma (Plasma) is a basic form of matter that exists widely in the nature of the universe except gas, solid and liquid. Under the action of external energy, such as heating, external electric field, laser irradiation At the same time, gas molecules or atoms will ionize, forming negatively charged electrons and positively charged ions. When the density of charged particles generated by ionization reaches a certain value, the ionized gas becomes a collection of charged particles and neutral particles The body has changed its original state.Because the total number of positive and negative ions of the ionized gas is equal at this time, the whole is electrically neutral, so it is called the fourth state of matter-the plasma state.
There are five main energy supply methods for generating plasma: electrical energy, thermal energy, nuclear energy, radiant energy, and mechanical energy.The ionization methods in the laboratory mainly include:
(1) The discharge method can generate various plasmas in different ionization states through the discharge of all frequency bands from DC to microwave.

(2) Combustion method thermally ionizes gas through combustion. For example, high-energy particles in a flame collide with each other to cause thermal ionization; in addition, the energy released by a specific thermochemical reaction can also cause gas ionization.

(3) The shock wave method compresses the gas sharply to generate high temperature, and the gas is thermally ionized to generate plasma.

(4) The energy required for ionization by light, X-rays, and β-ray irradiation is provided by light, X-rays, and β-rays.The initial charge of the discharge is ions generated by ionization.The charge density formed by this ionization method is generally low.

(5) The laser irradiation method can evaporate and ionize the substance by laser irradiation,

(6) The contact between the alkali metal vapor and the high temperature metal plate causes the alkali metal vapor to contact the high temperature metal plate to generate a plasma. When the gas contacts a metal with a larger ionization energy, ionization occurs. The ionization energy of the alkali metal vapor is small , So it is prone to ionization.

The plasmas used in industry are mainly divided into two types: one is a balanced "high temperature" plasma, that is, the temperature of the electrons in the system is equal to the temperature of the neutral particles, and the temperature can be as high as 5 × 103 ～ 2 × 104K; the other It is a non-equilibrium "low temperature" plasma, and its reaction is mainly excited by the kinetic energy of electrons. In actual work, the kinetic energy of electrons is mostly 1 ～ 10eV. The electron temperature in the system is as high as 104 ～ 105K. Plasma has been widely used in metal cutting, smelting and purification of high melting point metals. In recent years, the research of low temperature plasma applied to the surface treatment technology of textile materials is very active. Low temperature plasma is mainly generated by gas discharge, discharge The methods can be divided into corona discharge (Coronadischarge), glow discharge (Glowdischarge), dielectric barrier discharge (Dielectricbarrierdischarge), radio frequency discharge (Radiofrequencydischarge) and microwave discharge (Microwavedischarge).

However, most low-temperature plasmas are generated by gas discharge at a low pressure of several hundred Pa, and there are two important defects when applied to industrial production:
One is the inefficient batch processing. Because it is often necessary to open the vacuum processing chamber, take out the product and add samples, it is difficult to produce continuous. The second is that a complicated vacuum system is required and the investment is high. Although the corona in the air at atmospheric pressure, Both arc and dielectric barrier discharge can generate plasma, but corona discharge is a filamentary discharge, and the discharge is too weak, so the treatment is uneven and the efficiency is low; the arc discharge is too strong, which is easy to damage the test sample; dielectric barrier discharge usually consists of some The composition of the discharge filament with higher energy density makes it difficult to uniformly treat the material

Textile atmospheric pressure glow discharge plasma treatment technology printing and dyeing (2006No.21), and may also damage the sample. Therefore, the most suitable for industrial production is a uniform glow discharge with moderate power density (100mW / cm2) at atmospheric pressure, That is, the plasma generated by APGD (Atmos2phereGlowDischarge).

In the past 40 years, many documents have mentioned the use of plasma to change the surface properties of textiles. Some vacuum plasma DGPW has also proved the feasibility of industrial application of plasma, but its existence of vacuum equipment cannot meet the continuous production of the textile industry. As well as the problems of high cost and slow production speed, it cannot be used in actual production on a large scale. Only the plasma technology under atmospheric pressure can meet the requirements of the textile industry.
APGD laboratory sample test has been successful, but it still faces many problems when applied to mass production. For example, some textiles have a three-dimensional porous structure

Special properties; the fur, dust and other impurities contained on the surface of the fabric and large-scale surface processing, etc., will affect the plasma treatment effect

[1]. 2 corona discharge
2.1 The generation of corona discharge Corona discharge can work at atmospheric pressure or higher, but the voltage must be high enough to enhance the electric field at the corona part. Therefore, it is generally at high voltage (> 15kV) and higher frequency ( 20 ～ 40kHz). The corona is a self-sustained discharge. In corona discharge, the geometry of the electrode is very important, so the corona discharge is mostly in electrodes with a small radius of curvature, such as needle electrodes or wire electrodes. A high voltage is applied. The unevenness of the electric field limits the main ionization process to the vicinity of the electrode with a high local electric field, especially occurs near the electrode with a small radius of curvature or in a large or small thin layer, accompanied by obvious Bright, this area is called the ionization area, or corona layer or halo layer. Outside the corona layer, the electric field strength is very low, and no or little ionization occurs. The conduction of current depends on positive ions and negative ions or electrons The migration movement is usually called the migration zone or the peripheral zone. The minimum voltage required to form the corona discharge is called the halo voltage. The empirical calculation formula is [2 ～ 3]: U0 = 31md (1 + 0.308rd) Middle: U0 ——— Halo voltage, kV / cm;
M ——— The coefficient related to the surface state of the corona wire, the smooth surface is taken as 1, the rough surface is taken as 0.92, and the stranded metal wire is taken as 0.82;

d-relative air density (d = 0.0294p / T);

r ———— Corona radius of curvature;

p, T-local air pressure and temperature.

The polarity of the corona discharge depends on the polarity of the electrode with a small radius of curvature. If the electrode has a positive potential, the corona that occurs is called a positive corona; otherwise it is called a negative corona. When the voltage between them increases, flicker pulse corona, streamer corona, glow photoelectric will appear

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