Corona Discharge Technology Is Easy To Desizing For Polyester Sizing.

Host: Liang Feng

Guest: Professor Xu Weilin, vice president of Wuhan Textile University.

Moderator: Professor Xu, as you said, the surface properties of each fiber are very different. So how do we treat the six synthetic fibers differently in textile production and processing, and use different methods to realize the rapid surface treatment of fibers so as to make full use of fiber properties?

Xu Weilin: for the six synthetic fibers, the chemical structure has fewer hydrophilic groups, higher crystallinity and denser fiber surface.

A variety of oil additives have been added to the processing of synthetic fibers.

However, such practice can only be cured by temporary solutions.

Just like our common brush walls, the best putty is painted on the glass, and it will fall down soon. Then the putty is painted on the rough wall, and the bonding fastness is higher than that on the glass.

In the same way, sizing is like washing the putty powder on the wall. If the inert substance on the surface of the fiber exists, it will inevitably destroy the film when it is dried and divided. When the fabric is rewoven, it will be very serious if it is rubbed by the reed and the heald eye.

This is good for the workers in the weaving workshop.

Moderator: as a representative of synthetic fiber - polyester, which method do you use to achieve surface modification?

Xu Weilin: the use of polyester in synthetic fiber is increasing. Polyester fiber is used more and more in textile fibers because of its excellent mechanical and chemical stability. However, its dense surface structure and lack of hydrophilic functional groups make it very difficult to sizing. We have spent nearly 10 years to study the surface treatment and sizing technology of high voltage corona discharge on polyester and polyester cotton blended yarn. Remarkable results have been achieved, and its principle has been authorized by Chinese invention.

The surface modification of fibers can be divided into chemical modification, physical modification and plasma modification.

The traditional physical and chemical modification methods are long and the equipment occupies a large space.

Compared with chemical modification and physical modification, the corona equipment has small area and simple control.

The plasma is divided into high temperature, low temperature and mixed plasma. The mixed plasma is used at 5 or 10kV DC or AC high impedance at atmospheric pressure or slightly lower pressure, so that gas ionize to produce mixed plasma.

The charged particles generated by corona are constantly accelerating, increasing their energy continuously, and changing or pferring energy through collisions.

In addition, during the acceleration of particles, electrons can collide with some molecules in the air to form ozone and nitrogen oxides, and materials also produce free radicals.

When these energy or high-energy particles act on textile materials, they can produce heating, etching, forming free radicals, polymerization, crystallization and cross-linking, and a series of complex physical and chemical actions to modify the surface of textile materials.

The plasma produced by corona is a completely or partly ionized gas, which contains atoms, molecules, ions metastable and excited states, and the contents of electrons, negative ions and positive ions are approximately equal.

Because its composition and characteristics are different from ordinary gases, it is also called the fourth state of matter.

Because the ionizing component in the gas is more than 1/1000, their behavior is mainly controlled by Coulomb force between ions and electrons. The interaction between neutral particles replaces a secondary position, and the ionized gas is obviously affected by electric field and magnetic field.

Efficient and clean surface physical modification methods

Host: how to use corona discharge technology to achieve rapid surface treatment of polyester fiber?

Xu Weilin: corona discharge plasma and polyester fiber materials can be summarized in three steps:

The first step is that a small number of ions or free electrons in the air can be accelerated in high voltage electric field and get higher energy. When moving, it will impact other molecules in the space, and the energy will be enough enough to cause the molecules after collision to be ionized into new free ions, electrons, free radicals and other particles. The charged particles will continue to accelerate and collide with other molecules.

Other molecules can be gas molecules in the electric field, or they can be

In the second step, excited state molecules are unstable, decomposed into free radicals or dissociated into ions to absorb energy or retain their energy to metastable state.

The third step is the reaction of free radicals or ions on the surface of polyester fibers, which may lead to several situations: forming a dense cross-linking layer; polymerizing the plasma with the existing gas or monomer, and depositing on the polymer surface to form a design coating; the surface is formed by chemical reaction of the base or ion reaction and the surface of the etching material, forming a volatile reaction product, and the reaction product is detached from the surface of the etching material.

In short, corona discharge has a weak penetration ability to polyester, and it only acts on the shallow surface of ten to dozens of materials on the surface of the material. It has little influence on the bulk properties of the material, and is a highly efficient and clean material surface physical modification method. Corona treated materials are called green materials.

At the same time, the high-energy active particles produced by corona discharge can induce the fracture, degradation and oxidation of the molecular chains on the surface of the materials, resulting in etching reaction on the surface of the fibers and increasing the surface roughness. Ozone produced during corona discharge is a strong oxidant, which can oxidize the surface molecules and introduce hydrophilic groups.

The introduction of these groups will greatly help improve the hydrophilicity of the polyester surface. With the increase of corona voltage and corona time, the surface of the fiber is seriously etched and the more hydrophilic groups are connected to it.

When the voltage increases to a certain extent, corona discharge also has significant singeing effect.

It is helpful for sizing and desizing.

Moderator: compared with traditional practices, what benefits can this technology bring to the energy saving of machining ring?

Xu Weilin: after years of theoretical exploration and experiments, we have proved that corona treatment is correct.

On the basis of our joint experiment, Shandong Lu Tai Group has installed corona discharge equipment to pre treat yarn before the yarn entering the pulp tank of sizing machine. It can significantly improve the surface chemical activity of polyester, increase its surface hydrophilicity, and increase its specific surface area by etching.

In the very short time, the rapidly modified polyester yarns can be diffused on the surface of the yarns when they are immersed in the slurry, and some of the slurry penetrates into the yarns.

Under the action of the press roller, the slurry will form a good permeable layer in the yarn.

The active groups on the fiber surface form a good hydrogen bonding force with the slurry, firmly fixing the serosa onto the surface of the yarns.

The whiteness of the warp shaft produced during the weaving process was significantly reduced, and the number of broken ends was also significantly reduced.

After the production process is mature, it is found that corona discharge fast modification of yarn surface can also reduce the amount of polyvinyl alcohol slurry (PVA), which is of great help to the realization of sizing without PVA.

In addition, our team also found that corona discharge technology is helpful to desizing treatment.

At present, the amount of PVA is very high when sizing the warp yarns of high density and high density fabrics.

In the sizing formula of 60 yarns, the average dosage of PVA in factories is about 20 kg.

Desizing is a difficult problem at such a large dosage.

If PVA is not cleaned, it will have a great influence on fabric finishing, such as dyeing.

We use corona discharge equipment to process the grey cloth. The treated fabric and the untreated fabric are desizing under the same conditions. The experimental results show that the desizing rate after corona treatment is high.

In order to confirm that corona treatment is beneficial to desizing, we prepared PVA film and then conducted corona discharge on the film. Scanning electron microscopy (SEM) showed that the surface of the film was obviously etched.

Through the example of polyester, we know that the method of surface rapid processing is very important, and different fibers are used differently.

Corona discharge is used as an example. Corona discharge treatment before pure cotton yarn sizing has no effect on polyester and its blended yarn. This shows that for different fibers, we need to explore a fast processing method to adapt to its own properties.

Only in this way can we fully tap the potential of each fiber.