This article gives insight about the plasma treatment on textile material. It is one of the most economic and environment-friendly process. Plasma treatment is carried on natural fibre like wool, cotton as well as manmade fibres like polyester, polyamide etc. The methods of plasma treatment on yarns involves four processes like Cleaning Process, Activation Plasma Process, Deposition Process and Grafting Process.
Plasma treatment has been found to be much more efficient in terms of energy consumption, water consumption and so on as compared to traditional process. The advantages and disadvantages is also discussed. The objective of this article is to summarize the entire process of this new technology considering its effects on various parameters.
Introduction
The needs of the market and consumer demand drive dynamic changes in the textile industry. The textile industry has also shifted its focus away from conventional processes and toward environmentally friendly methods that produce the minimum waste products in response to growing environmental concerns. Plasma technology is one such example.A growing application of plasma technology is the treatment of textiles, which is accomplished by altering the surface of the materials without changing their bulk properties. The word "plasma," which means "something moulded or manufactured," is derived from the Greek language.
Plasma treatment of textiles is used to pre-treat fibres to increase wettability using Thierry's low-pressure systems, which enables solvent-free dyes to absorb and bond very strongly. Additionally, the coating of fabric with a specialised layer with different properties is done using plasma treatment of textiles. Plasma Treatment is a surface modification that adds functionality to textile materials by depositing chemical materials (plasma polymerization) or removing substances (plasma etching).
Plasmas can be classified into hot/thermal plasma and cold/non-thermal plasma depending on the temperature of the plasma zone. Only low-temperature plasmas are suitable for surface modification of heat-sensitive polymeric and textile materials.
Although the electron temperature in cold plasma can be much higher, the bulk temperature is essentially the ambient temperature. In high frequency devices (typically operating at frequencies of 40 kHz or 13.56 MHz) or using microwave generators, plasma can be produced between electrodes (2.45 GHz).
The plasma gas particles etch on the fabric surface in nano scale so as to modify the functional properties of the fabric.
What is Plasma?
Sir William Crookes in 1879 discovered the fourth state of matter ‘Plasma’ besides the three states solids, liquids and gases. Plasma lacks a defined shape or volume, much like a gas. Plasmas respond strongly to electromagnetic forces and are electrically conductive, producing magnetic fields and electric currents, unlike gases. It is assumed that virtually all electrons are "free" at extremely high temperatures, such as those found in stars, and that a very high-energy plasma is essentially bare nuclei swimming in a sea of electrons. This creates what is referred to as fully ionised plasma however, in reality it is partially ionized gas, composed of highly excited atomic, molecular, ionic and radical species with free electrons and photons.Plasmas can be classified into hot/thermal plasma and cold/non-thermal plasma depending on the temperature of the plasma zone. Only low-temperature plasmas are suitable for surface modification of heat-sensitive polymeric and textile materials.
Although the electron temperature in cold plasma can be much higher, the bulk temperature is essentially the ambient temperature. In high frequency devices (typically operating at frequencies of 40 kHz or 13.56 MHz) or using microwave generators, plasma can be produced between electrodes (2.45 GHz).
The plasma gas particles etch on the fabric surface in nano scale so as to modify the functional properties of the fabric.
Related article: Different types of textile finishes
Cleaning Process: Plasmas of inert (Ar, He) and oxygen are used. On the surface of the majority of industrial materials, the plasma-cleaning process eliminates organic contaminants like oils and other production releases by ablation. Under the influence of ions, free radicals, and electrons from the plasma, these surface contaminants, which are polymers, go through abstraction of hydrogen with free radical formation and repetitive chain scissions, until their molecular weight is sufficiently low to boil away in the vacuum.
Activation Plasma Process: It occurs when a surface is exposed to a gas that does not contain carbon, such as oxygen, ammonia, nitrous oxide, and others such as polyethylene. The primary outcome is the incorporation of various process gas substituent onto the treated material's surface. Almost any fibre or polymeric surface can be altered to give specific adhesives or coatings chemical functionality, greatly improving the adhesion properties and permanence. For instance, the production of technical fabrics has greatly improved thanks to the greatly improved adhesive strength and permanency that such activation of polymers provides.
Deposition Process: The term "plasma-enhanced chemical-vapour deposition" (PECVD) refers to a process that may be used when a more complex molecule is used as the process gas. When methane or carbon tetrafluoride is used in the gas phase, for instance, these coatings permanently change the surface properties of the material they are applied to. This produces a material deposition.
Grafting Process: Numerous free radicals must be produced on the surface of the material when an inert gas like argon is used as the process gas. If a monomer that can interact with the free radical is added to the reaction chamber, the monomer will graft. This is a low-pressure plasma treatment method, but atmospheric plasma processing can also produce grafting.
Methodology
Cleaning, activation, grafting, and deposition are the four main plasma processes that can be conveniently separated.Cleaning Process: Plasmas of inert (Ar, He) and oxygen are used. On the surface of the majority of industrial materials, the plasma-cleaning process eliminates organic contaminants like oils and other production releases by ablation. Under the influence of ions, free radicals, and electrons from the plasma, these surface contaminants, which are polymers, go through abstraction of hydrogen with free radical formation and repetitive chain scissions, until their molecular weight is sufficiently low to boil away in the vacuum.
Activation Plasma Process: It occurs when a surface is exposed to a gas that does not contain carbon, such as oxygen, ammonia, nitrous oxide, and others such as polyethylene. The primary outcome is the incorporation of various process gas substituent onto the treated material's surface. Almost any fibre or polymeric surface can be altered to give specific adhesives or coatings chemical functionality, greatly improving the adhesion properties and permanence. For instance, the production of technical fabrics has greatly improved thanks to the greatly improved adhesive strength and permanency that such activation of polymers provides.
Deposition Process: The term "plasma-enhanced chemical-vapour deposition" (PECVD) refers to a process that may be used when a more complex molecule is used as the process gas. When methane or carbon tetrafluoride is used in the gas phase, for instance, these coatings permanently change the surface properties of the material they are applied to. This produces a material deposition.
Grafting Process: Numerous free radicals must be produced on the surface of the material when an inert gas like argon is used as the process gas. If a monomer that can interact with the free radical is added to the reaction chamber, the monomer will graft. This is a low-pressure plasma treatment method, but atmospheric plasma processing can also produce grafting.
Examples of Plasma Treatment
Plasma treatment is a surface treatment applied on protein fibres like wool, cellulosic materials such as cotton as well as synthetic fibres. Few examples of this process is discussed below:1. Plasma Treatment of Wool to achieve Shrink-Resistant
Wool's morphology is extremely complex; this complexity extends not only to the fibre stem but also to the fibre surface. A directional frictional coefficient is created by the overlap of cuticle cells. Because wool naturally repels water, the hydrophobic effect in aqueous media causes fibres to aggregate and move toward their root end, which results in felting and shrinkage. The surface of wool after plasma treatment is altered in two ways. The hydrophobic lipid layer at the surface is first oxidised and partially removed, affecting both the covalently bound 18-methyl-eicosanoic acid and the adhering external lipids.Due to the presence of disulfide bridges, wool's exocuticle is highly cross-linked, and plasma treatment significantly reduces the cross-link density by oxidising the disulfide bonds. Without affecting the strength of the fibres or protein loss, the hydrophobic nature of wool's surface changes to become increasingly hydrophilic as it oxidises.
Wool top's shrinkage behaviour is reduced as a result of chemical and physical surface modification along with reduction in felting. It should be mentioned that the plasma treatment brings additional advantages, in particular, increasing dyeing kinetics, an enhanced depth of shade, and an improved bath exhaustion
2. Treatment of Cotton with different kinds of Plasma Gases
Cotton's specific surface area increases after being treated with oxygen plasma, just like it did with wool. On the other hand, hexamethyldisiloxane (HMDSO) plasma treatment results in a smooth surface with an increased water contact angle of up to 130°. As a result, hydrophobization has a strong effect. The surface composition of the fibres clearly shows the presence of fluorine when a hexafluoroethane plasma is used in place of an HMDSO plasma, and the substance becomes extremely hydrophobic.However, the hydrophobization has no effect on the transmission of water vapour. The combination of increased specific surface area and hydrophobization produces the phenomenon known as the "Lotus effect," in which the lotus' double layer reduces the surface's area in contact with dirt particles while the hydrophobicity of the surface shields the material from dust and dirt. The lotus effect can even keep extremely viscous fluid from sticking to its surface.
3. Plasma Treatment on Synthetic fibres
Polypropylene (PP) is a very intriguing material for plasma treatment because it has an extremely low surface tension and is highly hydrophobic. However, PP is employed in numerous technical applications where better wettability or adhesion properties are advantageous.The wettability of non-woven PP filters can be greatly enhanced by using an oxidative plasma with a relatively short treatment period because water cannot pass through the PP-web without the application of high pressure. Air and NH3-plasma were used instead of oxidative plasma because there was little difference in wettability that could be seen. Similar to PP, treatments in air, O2, and NH3 plasma are typically carried out on polyethylene PE, polyethylene terephthalate PET, and polytetrafluoroethylene PTFE. To some extent, these treatments can raise wettability.
Dyeability, wettability, and surface characteristics are the main research topics for the plasma treatment of polyamide. In order to improve dyeability and wettability, oxygen and air plasma are used.
The plasma treatment of textiles has many benefits over the conventional wet processing of textiles, including the following:
1. By selecting the appropriate gases or chemicals, countless chemical modifications are possible.
2. Reducing water use lowers the amount of waste water produced and the cost of waste water treatment.
3. Due to its low chemical consumption and lower chemical and water costs, it has a financial advantage over the traditional wet processing.
4. The improvement of the surface characteristics of textile materials without changing their innate properties.
5. All plasma processing is less hazardous to the environment than wet processing of textiles for the reasons mentioned above, closed plasma treatment systems are even more environmentally friendly because the plasma by-products can be captured rather than released into the environment.
6. Almost any substrate can be used to deposit thin films that are uniform, pore-free, and possess superior properties that aren't possible with traditional chemistry.
Disadvantages of plasma treatment in textile
1. One of the most significant drawbacks of plasma therapy is system dependency. This means that even with the same flow rate, gas pressure, and power input, the required amount of reacting species may not be produced.
2. For each process and piece of equipment, ideal process parameters must be established.
3. Initial investments like the purchase of pricey plasma equipment and high vacuum pumps are viewed as stumbling blocks and may even be disadvantageous.
4. Treating thin surface layers without altering the bulk may be advantageous when the goal is to keep the bulk untreated and only thin surface treatment is required, but it may also be disadvantageous for some end uses.
References:
4. Plasma Treatment on Nylon 6
Dyeability, wettability, and surface characteristics are the main research topics for the plasma treatment of polyamide. In order to improve dyeability and wettability, oxygen and air plasma are used.
How Plasma Treatment is different from Conventional methods?
Advantages and Disadvantages of Plasma Treatment
Advantages of plasma treatmentThe plasma treatment of textiles has many benefits over the conventional wet processing of textiles, including the following:
1. By selecting the appropriate gases or chemicals, countless chemical modifications are possible.
2. Reducing water use lowers the amount of waste water produced and the cost of waste water treatment.
3. Due to its low chemical consumption and lower chemical and water costs, it has a financial advantage over the traditional wet processing.
4. The improvement of the surface characteristics of textile materials without changing their innate properties.
5. All plasma processing is less hazardous to the environment than wet processing of textiles for the reasons mentioned above, closed plasma treatment systems are even more environmentally friendly because the plasma by-products can be captured rather than released into the environment.
6. Almost any substrate can be used to deposit thin films that are uniform, pore-free, and possess superior properties that aren't possible with traditional chemistry.
Disadvantages of plasma treatment in textile
1. One of the most significant drawbacks of plasma therapy is system dependency. This means that even with the same flow rate, gas pressure, and power input, the required amount of reacting species may not be produced.
2. For each process and piece of equipment, ideal process parameters must be established.
3. Initial investments like the purchase of pricey plasma equipment and high vacuum pumps are viewed as stumbling blocks and may even be disadvantageous.
4. Treating thin surface layers without altering the bulk may be advantageous when the goal is to keep the bulk untreated and only thin surface treatment is required, but it may also be disadvantageous for some end uses.
Application of Plasma Treatment
To cause the ionisation of plasma gas for textile treatment, various techniques can be used:- Glow-discharge method – Low pressure results in the production of plasma gas. Direct electric current with a low frequency is used over two electrodes in the methodology.
- Corona discharge method – Applying a low frequency or pulsed high voltage over an electrode pair will generate plasma gas at atmospheric pressure.
- Dielectric barrier discharge method – An electrode pair with at least one covered by a dielectric material is exposed to a pulsed voltage to create plasma gas.
- Different industrial applications for low-temperature plasma technology, such as low glow discharge under reduced pressure and dielectric barrier discharge under normal pressure, have been well established. Desizing of woven fabrics, functionality addition, and alteration of the surface characteristics of textile materials are all examples of applications for textiles.
Conclusion
Plasma technology provide a versatile, adaptable, clean, and environmentally friendly finishing method for giving textile substrates the much-desired functional properties they need to satisfy particular requirements. As a result, plasma treatment can be seen as a sustainable alternative to the traditional chemical finishing of textile materials because it effectively eliminates the discharge of harmful chemicals. Innovative surface properties that are outside the scope of conventional wet chemistry finishing can be produced using plasma treatment. Therefore, plasma technology can significantly contribute to innovation, new products, and sustainable growth.References:
- https://www.fibre2fashion.com/industry-article/3884/plasma-treatment-technology-for-textile-industry
- https://austinpublishinggroup.com/textile-engineering/fulltext/arte-v3-id1019.pdf
- https://www.thierry-corp.com/plasma-knowledgebase/plasma-treatment-of-textiles
- https://learn.destexproject.eu/wp-content/uploads/2021/03/Plasma-treatment-in-the-textile-industry_UB.pdf
- https://plasmatreatment.co.uk/industry-sectors/textiles-fabric
- https://link.springer.com/content/pdf/10.1007/s10853-015-9152-4.pdf
- https://www.ispc-conference.org/ispcproc/ispc21/ID453.pdf
- https://www.textilesphere.com/2019/08/plasma-technolgy-in-textiles.html
- https://texeducation.wordpress.com/2014/04/22/plasma-treatment-of-textiles-i/
About the Author:
Adita Banerjee is pursuing her graduate degree in Textile Technology from the Government College of Engineering and Textile Technology, Serampore. She loves writing content and reading books.