Comment on textile atmospheric pressure glow discharge plasma treatment technology

The generation of plasma and the application of plasma (Plasma) are a basic form of the material that exists in the universe in addition to the gaseous state, solid state and liquid state. Under the action of external energy, such as heating, external electric field, laser irradiation When isochronous, gas molecules or atoms are ionized to form negatively charged electrons and positively charged ions. When the density of charged particles produced by ionization reaches a certain value, the ionized gas becomes a collection of charged particles and neutral particles. The body changes its original state. Since 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 the substance—the plasma state.
The energy supply path for generating plasma mainly includes five kinds of electric energy, thermal energy, nuclear energy, radiant energy and mechanical energy. The ionization methods in the laboratory mainly include:
(1) The discharge method can generate plasmas of various ionization states by discharging from all the frequency bands from DC to microwave.

(2) Combustion method by means of combustion, the gas is thermally ionized. For example, high-energy particles in the 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 generates a high temperature by rapidly compressing the gas, causing the gas to be thermally ionized to generate a plasma.

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

(5) Laser irradiation method can evaporate and ionize by laser irradiation.

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

The plasma used in industry is mainly divided into two types: one is to balance the "high temperature" plasma, that is, the electron temperature in the system is equal to the neutral particle temperature, and the temperature can be as high as 5×103～2×104K; For the non-equilibrium "low temperature" plasma, the reaction is mainly excited by electron kinetic energy. In actual work, the electron kinetic energy is mostly 1 ~ 10eV, the electron temperature in the system is as high as 104 ~ 105K, and the ion temperature is only a few Baidu or even close to room temperature. Plasma has been widely used in metal cutting, smelting and purification of high melting point metals. In recent years, low temperature plasma is very active in the surface treatment technology of textile materials. Low temperature plasma is mainly generated by gas discharge, discharge The method can be divided into Coronadischarge, Glowdischarge, Dielectric barrier discharge, Radiofrequency discharge and Microwavedischarge.

However, most low-temperature plasmas are produced by gas discharge at a low pressure of several hundred Pascals. There are two important drawbacks in industrial production:
The first is the low-efficiency batch processing method. Since it is often necessary to open the vacuum processing chamber, take out the product and add the sample, it is difficult to produce continuous. Second, it requires a complicated vacuum system, and the investment is higher. Although atmospheric pressure, corona in the air, Both the arc and the dielectric barrier discharge can generate plasma, but the corona discharge is a filament discharge, and the discharge is too weak, so the treatment is uneven, the efficiency is low; the arc discharge is too strong, and the sample is easily damaged; the dielectric barrier discharge is usually owned by some Composition of higher energy density discharge filaments, making it difficult to evenly materialize

The textile normal pressure glow discharge plasma treatment technology printing and dyeing (2006 No. 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 literatures have mentioned the application of plasma to change the surface properties of textiles. Some vacuum plasma DGPW also proves the feasibility of plasma industrial application, but its vacuum equipment can not meet the continuous production of textile industry, As well as the problems of high cost and slow production speed, it can not be used in real production on a large scale. Only plasma technology under atmospheric pressure can meet the requirements of textile industry production.
The APGD laboratory sample test has been successful, but it still faces many problems in high-volume production. For example, some textiles have a three-dimensional porous structure.

Special properties; the surface of the fabric contains hair, dust and other impurities and large-area surface processing, etc., will affect the plasma treatment effect

[1].2 Corona discharge
2.1 Corona discharge generation Corona discharge can work at atmospheric pressure or higher, but the voltage must be high enough to enhance the electric field at the corona. Therefore, it is generally at high voltage (>15kV) and higher frequency ( Corrosion is carried out under conditions of 20 to 40 kHz. Corona is a self-sustaining discharge. In corona discharge, the geometry of the electrode is very important, so corona discharge is mostly at an electrode with a small radius of curvature, such as a needle electrode or a wire electrode. Applying a high voltage. The non-uniformity of the electric field limits the main ionization process to the vicinity of the electrode where the local electric field is high, especially in the vicinity of 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 ionized area, or called the corona layer or the halo layer. Outside the corona layer, the electric field strength is very low, no or little ionization occurs. The conduction of current depends on positive ions and negative ions or electrons. The migration movement, usually called the migration zone or the peripheral zone. The minimum voltage required to form a corona discharge is called the halo voltage. The empirical formula is [2~3]: U0=31md(1+0.308rd) Medium: U0———haling 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 twisted metal wire is taken as 0.82;

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

r———the radius of curvature of the corona line;

p, T———local 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 positive corona; otherwise it is called negative corona. In the case of positive corona, with the pole When the voltage is increased, there will be a flicker pulse corona, flow photoglow, and Huiguang

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