Plasma Technology in Textile: A Step Towards the Green Environment

Last Updated on 06/04/2021

Plasma Technology in Textile: A Step Towards the Green Environment

Arpita Kothari
M. Tech. Scholar
Department of Textile Technology,
NIT Jalandhar, India
Email: geniousarpita@gmail.com

 

1. Introduction:
The textile industry is searching for innovative production techniques to improve the product quality, as well as society requires new finishing techniques working in environmental respect. Plasma surface treatments show distinct advantages, because they are able to modify the surface properties of inert materials, sometimes with environment friendly devices. For fabrics, cold plasma treatments require the development of reliable and large systems. Such systems are now existing and the use of plasma physics in industrial problems is rapidly increasing. On textile surfaces, three main effects can be obtained depending on the treatment conditions: the cleaning effect, the increase of microroughness (anti-pilling finishing of wool) and the production of radicals to obtain hydrophilic surfaces. Plasma polymerisation, that is the deposition of solid polymeric materials with desired properties on textile substrates, is under development. The advantage of such plasma treatments is that the modification turns out to be restricted in the uppermost layers of the substrate, thus not affecting the overall desirable bulk properties.

Plasma, the 4th state of matter is not so a strange thing, It had been first developed by M. Faraday in 1880s and plasma concept was first proposed by I. Langmuir in 1926. In the 1960s, the main industrial applications of (low-pressure) plasmas have been in the micro-electronic industries. In the1980s their uses broadened to include many other surface treatments, especially in the fields of metals and polymers. In 1980s, in the textile field, low-pressure plasma treatments of a variety of fibrous materials showing very promising results regarding the improvements in various functional properties in plasma-treated textiles. In recent times, commercial applicable atmospheric-pressure plasma processing of textiles is under research.

What is Plasma?
Plasma is any substance (usually a gas) whose atoms have one or more electrons detached when heat is applied and therefore become ionised. The detached electrons remain, however, in the gas volume that in an overall sense remains electrically neutral. Thus, any ionised gas that is composed of nearly equal numbers of negative and positive ions is called plasma.

Plasma: 4th state of matter
Figure 1: Plasma: 4th state of matter

The conventional wet treatments applied in textile processing for fibre surface modification and others are associated with many constraints. These treatments mainly concern with energy, cost and environmental issues. Application of Plasma technology at low temperature in textile processing can prove to be the best alternative for these issues. Unlike conventional wet processes, which penetrate deeply into fibres, plasma only reacts with the fabric surface that will not affect the internal structure of the fibres. Plasma technology modify the chemical structure as well as the surface properties of textile materials, deposit chemical materials (plasma polymerization) to add up functionality, or remove substances (plasma etching) from the textile materials for better applicability. The functional properties of the fabric can be modified by Nano scale etching of surface by plasma gas particles. In textile processing, this technology can be explored in various areas like pre-treatment, dyeing and finishing through different methodology vis-à-vis Glow-discharge method, Corona discharge method and Dielectric barrier discharge method to add functionality and modification of surface properties of textile materials. Plasma technology is applicable to most of textile materials for surface treatment and is beneficial over the conventional process, since it does not alter the inherent properties of the textile materials, it is dry textile treatment processing without any expenses on effluent treatment, It is a green process and it is simple process. This technology can generate more novel products to satisfy customer’s need and requirement.

Gases commonly used for plasma treatments are:

  • Chemically inert (e.g. helium and argon).
  • Reactive and non-polymerisable (e.g. ammonia, air, and nitrogen).
  • Reactive and polymerisable (e.g. tetra fluoroethylene, hexamethyl disiloxane).

Principle of Plasma Processing:
Plasma technology is a surface-sensitive method that allows selective modification in the nm-range. If a textile to be functionalized is placed in a reaction chamber with any gas and the plasma is then ignited, the generated particles interact with the surface of the textile. In this way the surface is specifically structured, chemically functionalized or even coated with nm-thin film depending on the type of gas.

Types of Plasma:
Different plasma based on different things are shown in table 1.

Table 1: Types of Plasma

On the basis of pressureLow pressure (0.01kpa)
Atmospheric pressure (100 kpa)
On basis of the temperature of electrons and ionsHot plasma (above 10000 degree)
Cold plasma (below 100 degree)
On basis of frequency of power supplyLow frequency (40kHz)
Radio frequency (13.56MHz)
Microwave frequency (2.56GHz)

2. Plasma Technologies:

2.1. Low pressure cold plasma technology:
Low-pressure cold plasma technology is also referred to as vacuum plasma technology. This technology has its origin in the processing of semiconductor materials and printed circuit boards (PCB). Soon after its introduction in the electronics industry, the path to incorporation into the textile and nonwoven sectors has been and remains troublesome.

The plasma state of a gas – also considered as the fourth aggregation state of matter – can be reached if the gas is under sufficiently low-pressure and when electromagnetic energy is provided to the gas volume. Under those circumstances, the process gas will be partially decomposed into radicals and atoms and will also be partially ionised. Depending on the frequency of the electromagnetic energy, the pressure range in which equilibrium with a high density of charged particles is reached might be different. For the radio frequency range (typically 40 kHz or 13.56 MHz), normally the working gas pressure is kept in the lower 0.1 mbar range, whereas for microwave sources, a working pressure between 0.5 and 1 mbar is often used. In order to effect the plasma treatment in sufficiently pure process gas conditions, a base pressure in the lower 0.01 mbar needs to be reached. This can be done with two-stage roughing vacuum pumps (rotary vane type) or with a dry pump or with a combination of either of those pumps with a roots blower.

Plasma can bring several effects to substrates, depending on the plasma mode and the process gases used. There are five major effects fine cleaning, surface activation, etching, cross-linking and coating deposition.

Equipment based on this:

Roll-to-Roll batch plasma systems.
Figure 2: Roll-to-Roll batch plasma systems.
True roll-to-roll web treatment
Figure 3: True roll-to-roll web treatment

Development of type of low-pressure plasma is done by:

2.1.1. Glow discharge:
It is the oldest type of plasma technique. It is produced at reduced pressure (low-pressure plasma technique) and provides the highest possible uniformity and flexibility of any plasma treatment. The plasma is formed by applying a DC, low frequency (50 Hz) or radio frequency (40 kHz, 13.56 MHz) voltage over a pair or a series of electrodes. (Figure 2, 3) Alternatively, a vacuum glow discharge can be made by using microwave (GHz) power supply.

2.2. Atmospheric-pressure cold plasma processing technology:
Low pressure plasma processing has failed to make an impact in the textile sector because of a particular constraint, which is incompatible with industrial mass production. All the technologies developed to date are based on the properties of low-pressure plasmas.

The process must take place in an expensive, closed-perimeter vacuum system and cannot be used for continuous production lines operating at room temperature, with machines processing fabric 2-meter-wide at high speed.

To overcome these restraints, Atmospheric Pressure Plasma Techniques are being developed. This technique provides the highest possible plasma density (in the range of 1 to 5 x 1012 electrons cm-3), without the associated high gas temperatures and the cold plasma chemically treats fabric and other substrates without subjecting them to damaging high temperatures. The Atmospheric Pressure Plasma is a unique, non-thermal, glow-discharge plasma operating at atmospheric pressure. The discharge uses a high-flow feed-gas consisting primarily of an inert carrier gas, like He, and small amount of additive to be activated, such as O2, H2O or CF4.

The development of three types of APP that have relevance for textile treatment – the Corona Discharge, the Dielectric Barrier Discharge, the Atmospheric Pressure Glow Discharge.

2.2.1. The Corona Discharge:
Corona discharges are plasmas that result from the high electric field that surrounds an electrically conductive spatial singularity when a voltage is applied. The high electric field around the singularity, i.e. the point of the needle or the wire, causes electrical breakdown and ionisation of whatever gas surrounds the singularity, and plasma is created, which discharges in a fountain-like spray out from the point or wire. Plasma types are characterized, inter alia, by the number, density and temperature of the free electrons in the system.

The discharge is so narrow that the residence time of the fabric in the plasma would be too short for commercial operation and, in addition, the power level that can be applied is extremely limited by the cross-section capacity of the wire and its ability to dissipate heat generated during treatment. Accordingly, in its pure form, corona is far from an ideal textile surface processing medium.

Corona discharge
Figure 4: Corona discharge

2.2.2. Dielectric barrier discharge:
In contrast to the asymmetry of the corona system, if a symmetrical electrode arrangement is set up comprising two parallel conducting plates placed in opposition, separated by a gap of ∼10 mm, and a high voltage, 1–20 kV, is applied, the gas between the plates can be electrically broken down and a plasma discharge generated. Generally, however, that plasma takes the form of a hot thermal plasma arc less than a millimetre in diameter, which jumps from one spot on one electrode plate to a spot on the opposing electrode. This is useless for textile treatment and would do nothing except burn a hole in the fabric. If, however, one or both of the electrode plates is covered by a dielectric such as ceramic or glass, the plasma finds it much more difficult to discharge as an arc and, instead, is forced to spread itself out over the area of the electrodes to carry the current it needs to survive. This type of plasma is called a Dielectric Barrier Discharge (DBD) and is large area, non-thermal and uniform. Because of charge accumulation on the dielectric, this tends to neutralise the applied electric field thus choking off the plasma, the DBD must be powered by a.c. and is typically driven by high voltage power supplies running at frequencies of 1 to 100 kHz. It is denser than the corona with a typical free electron density of about 1010 electrons/cm3 but the free electrons are slightly cooler at temperatures of 20 000 to 50 000 K. This is a much more attractive candidate for textile processing than the pure corona.

Dielectric barrier discharge
Figure 5: Dielectric barrier discharge

2.2.3. The atmospheric pressure glow discharge:
The third APP type intrinsically capable of meeting the size and temperature constraints needed for textile processing is the Atmospheric Pressure Glow Discharge (APGD). This is analogous in its mode of generation and some key characteristics to the famous low-pressure glow discharge plasma that is the backbone of the global plasma industry and workhorse of a dozen major industries, in particular the omnipresent microelectronics industry, which would not exist without the glow discharge plasma. The APGD is generated by application of relatively low (∼200 V) voltages across opposing symmetrical planar or curved electrodes, separated by mm at high frequency, or even very high frequency, radio frequencies 2–60 MHz, much higher than the other plasma types. The electrodes are not covered by dielectric but are bare metal, a feature that enables significantly higher power densities (up to 500 W/cm3) to be coupled into the discharge than can be achieved with corona or DBD.

The APGD is denser than the DBD, with typical free electron densities of 1011–1012 electrons/cm3, but the free electrons are slightly cooler at temperatures of 10000 to 20000 K. Textile treatment temperatures can run at 25–50ºC. APGD plasma takes the form of a bright, uniform, homogeneous glow in the region between the electrodes. The application of voltage between metal plates would generally result in generation of a highly undesirable, very high current density and hot plasma arc. By control of the interelectrode gap and the frequency of the driving voltage and, above all, by the use of helium as ∼99% of the generation gas, arcing is prevented and a large volume, non-thermal plasma is generated, which is both dense and a rich source of the chemical species needed to carry out textile processing. This amazing gas has several special properties that, in combination, make it uniquely suited for the generation of well-behaved, large volume, cool plasma at atmospheric pressure. Other gases, such as oxygen or nitrogen, are microscopically more complex with many different energetic modes.

All in all, helium has been and continues to be probably the best medium for non-thermal APP research as well as being technologically valuable as a route to useful large volume, cool plasmas.

Atmospheric pressure glow discharge
Figure 6: Atmospheric pressure glow discharge

3. Effect of Plasma on Textile Surface:
There are five major effects of which three will be described in detail: fine cleaning, surface activation, and etching, cross-linking and coating deposition.

3.1. Surface activation by plasma:
Surface activation by plasma is also referred to as chemical grafting (Terlingen, 1993). It never occurs alone, but always occurs during/after plasma cleaning. Indeed, in the case of a substrate subjected to a soft secondary plasma which contains reactive species (e.g. oxygen atoms), the effect of those atoms will be twofold: they will react with organic contamination which is present on the substrate surface. Such organic contamination consists, in many cases, of loosely bound hydrocarbons. Both H and C will react with oxygen and will leave the substrate surface in the form of volatile H2O and CO2. Once the surface molecules of a polymer are freed from contamination, they can react with the oxygen atoms which will form carbonyl-, carboxyl- or hydroxyl functional groups on the substrate surface. It is said that the polymer surface has been chemically functionalised.

The effect of grafting carbonyl-groups onto a surface of PP, polyethylene (PE), or polyesters such as polyethy leneterephthalate (PET) or polybutyleneterephthalate (PBT) gives rise to an increase in surface energy to levels higher than 68 mN/m immediately after the plasma treatment. This effect is, however, not permanent: it has a certain shelf-life. Once the substrate has been removed from the plasma, and depending on the storage conditions, oxygen atoms will be released again from the surface molecules. This will happen slowly over time. After several days or even several months, the original surface energy of the substrate will have returned. The rate at which this happens depends on the type of substrate: e.g. PP has a fairly good shelf-life of a couple of weeks, whereas silicones show a shelf-life of less than one day. It further depends on the plasma conditions: an intensive plasma treatment will create a higher surface density of functional groups and, as such, the shelf-life will be longer.

Plasma activation is being used in several fabric and nonwoven applications in the textile industry:

  • Fabrics for automotive and medical applications
  • Pre-treatment before dyeing
  • Activation of transportation textile before application of flame-retardant chemistry

3.2. Etching by plasma:
In order to perform an efficient etching process, a direct plasma is normally needed. In such a configuration, the substrate is bombarded with charged particles (ions and electrons) and apart from a purely chemical effect; the substrate is subjected also to a physical sputtering effect. In the case of textiles and nonwovens, this effect of plasma treatment is not often used.

However, there is a certain potential even for fabrics. The textile market is trying to make deep, dark colours and this is not easy to achieve. One way to do this is to reduce the specular component of reflection of the fabric surface after dyeing. A plasma etching leads to a controlled Nano- or micro-roughness, increasing diffuse reflectance and minimising the specular component. In consequence, the dyed fabric will have an intenser darker colour after plasma etching.

Etching requires the removal of several hundreds of nanometres and etching processes are therefore slow. Needless to say, this technique is only viable for very high-end textiles.

3.3. Thin film deposition by plasma polymerisation:
A very important usage of low-pressure vacuum plasma technology is thin film coating deposition by plasma polymerisation. In this specific case, reactive precursor gases that can polymerise are being used as process gases (Yasuda, 1976). The precursor gases are broken into radicals that react with each other on the substrate surface. The nature of the precursor gases will very much determine the properties of the deposited coating. Coating thickness is normally in the 10–50 nm range (5–30 molecular layers).

The very first applications of plasma polymerisation were found in the medical device industry. There are many industrial applications of thin film deposition by plasma polymerisation in the technical textile and nonwoven industry. Roughly, the coatings deposited in those industries can be categorised under either (permanently) hydrophilic coatings or hydrophobic/oleo phobic coatings. In most cases, the deposited coatings give rise to unique products that are difficult or even impossible to produce using other technologies.

Application of deposition by plasma on textile:

  • Hydrophobation of nonwovens for filtration applications
  • Hydrophilic coatings on nonwoven PP for battery separators

4. Application of Plasma Technology in Textile:
Due to high restriction in the control of chemical processing of textile materials, the new and innovative textile treatments are demanded. In this regard, plasma technology shows distinct merits due to its environmental friendly and better treatment results.

Various eras where this technology can be explored includes pre-treatments, other wet processes of textiles, technical textile and non-woven. Plasma can modify the surface properties of textile materials, deposit chemical materials (Plasma polymerisation) to add up functionality, or remove substances (plasma etching) from the textile materials and used to produce innovative functional textiles.

4.1. Desizing of cotton fabric:
Plasma technology can be used to remove PVA sizing material from cotton fibres. In conventional desizing process we use chemicals and hot water to remove size. But desizing with plasma technology we can use either O2/He plasma or Air/He plasma. Firstly, the treatment breaks down the chains of PVA making them smaller and more soluble. X-ray photoelectron microscopy results reveal that plasma treatment introduces oxygen and nitrogen groups on the surface of PVA which owing to greater polarity increase the solubility of PVA.

Of the two gas mixtures that were studied, the results also indicate that O2/He plasma has a greater effect on PVA surface chemical changes than Air/He plasma.

4.2. Dyeing
Several studies have shown that dye ability or printability of textiles can be markedly improved by plasma treatments. This effect can be obtained on both synthetic and natural fibres. Capillarity improvement, enhancement of surface area, reduction of external crystallinity, creation of reactive sites on the fibres and many other actions can contribute to the final effect depending on the operative conditions. Also, production of colours on fibres exploiting diffraction effects has been attempted.

4.2.1. Dyeability of Natural Fibres:
It has been reported that plasma treatment on cotton in presence of air or argon gas increases its water absorbency which in turn increase both the rate of dyeing and the direct dye uptake in the absence of electrolyte in the dye bath.

The contributory factors leading to this increase in dye uptake can be: i. The change of the fabric surface area per unit volume due to the surface erosion. ii. The etching effect of the plasma effect on the fibred mages the fiber surface and also removes surface fiber impurities (e.g. cotton wax or any remaining warp size, etc.). iii. The chemical changes in the cotton fiber surface (leading to carbonyl and carboxyl groups in the fiber. iv. The possibility of the formation of free radicals on the cellulosic chains of cotton. v. Thus the action of oxygen and air plasma treatments modifies the surface properties of cotton and leads to an increase in the rate and extent of uptake of direct dye.

The dye exhaustion rate of plasma treated wool has been shown to increase by nearly 50%. It has been shown that O2 plasma treatment increases the wetability of wool fabric thus leading to a dramatic increase in its wicking properties. Also, the disulphide linkages in the exocuticle layer oxidize to form sulphonate groups (which are act as active sites for reactive dyes) which also add to the wetability. The etching of the hydrophobic epicuticle and increase in surface area also contributes towards the improvement in the ability of the fibers to wet more easily.

4.2.2. Dyeability of Synthetic Fibres:
In the synthetic fibres, plasma causes etching of the fibre and the introduction of polar groups leading to improvement in dyeability. This has been evaluated through in situ polymerization of acrylic acid in case of polyester, polyamide and polypropylene fabrics. Plasma-induced surface modification of microdenier polyester produces cationic dyeable polyester fiber. The researchers believe that this technique can lead to a continuous flow system, low energy consumption, and more environmentally friendly consumption, low temperature dyeing technology on polyester substrates.

Polyamide (nylon 6) fabrics have been treated with tetrafluoromethane low temperature plasma and then dyed with commercially available acid and dispersed dyes. Dyeing results showed that the plasma treatment slows down the rate of exhaustion but does not reduce the amount of absorption of acid dyes. The dyeing properties of disperse dyes on plasma treated nylon fabric charged markedly when compared with untreated fabric. A slight improvement in colorfastness was seen with the treated sample.

4.3. Textile finishing:
Unlike wet finishing processes, which penetrate deep into the fibres, plasma treatment is restricted to surface reaction and limited to a surface layer of around 100 Ao. Because of this various functionality and properties can be imparted to both natural fibers and polymers, as well as to non-woven fabrics, without having any adverse effect on their internal structures.

This leads to produce various types of functional textiles. Various finishing applications of plasma in textiles are given in table-2.

Table 2: Various application of plasma in textile finishing

APPLICATIONMATERIALTREATMENT
Hydrophilic finishPP, PET, PEOxygen plasma, Air plasma
Hydrophobic finishCotton, P-C blendSiloxane plasma
Antistatic finishRayon, PETPlasma consisting of dimethyl silane
Reduced feltingWoolOxygen plasma
Crease resistanceWool, cottonNitrogen plasma
Improved capillarityWool, cottonOxygen plasma
UV protectionCotton/PETHMDSO plasma
Flame retardancyPAN, Cotton, RayonPlasma containing phosphorus

Plasma can be used for grafting molecules on the fibre surface to impart special functionality to textiles. Hydrophobic character to lightweight cotton fabric can be done by polymerization using microwave plasma. A polymer layer of about 100 Ao thick is deposited on the cotton fibre surface as a result of this plasma assisted grafting and polymerization. Europlasma, CD Roll 1100/600, CD Roll 1800/600 are some machines based on plasma system tailored for textile surface finishing, developed in Belgium14. The costs of these devices are very high, If the cost factor is eliminated, this technology will be very important for textile finishing industry.

4.4. Bio-Medical Applications:
New medical products, materials and surgical procedures keep improving current health-care practices. Plasma surface modification can improve biocompatibility and bio functionality. The use of synthetic materials in biomedical applications has increased dramatically during the past few decades. Although most synthetic biomaterials have the physical properties that meet Surface Modification Methods. Modifying the surface of a material can improve its biocompatibility without changing its bulk properties.

Several methodologies have been considered and developed for alter the interactions of biomaterials with their biological environments; plasma surface modification is one of these methodologies. The Process In the plasma surface modification process, a glow discharge plasma is created by evacuating a vessel, usually quartz because of its inertness, and then refilling it with a low-pressure gas, the gas is then energized using techniques such as radio-frequency energy, microwaves, alternating current of direct current. The energetic species in a gas plasma include ions, electrons, radicals, meta stables, and photons in the short-wave ultraviolet (UV) range. Surfaces in contact with gas plasmas are bombarded by these energetic species and their energy is transferred from the plasma to the solid, these energy transfers are dissipated within the solid by a variety of chemical and physical processes as schematically to result in the surface modification.

4.5. Antifelting of wool:
Felting is an essential issue of wool garment due to the fibre scales. Conventional anti-felting gives negative effects on hand feel and environmental issues. Oxygen plasma gives anti-felting effect on wool fibre without incurring traditional issues.

4.6. Water repellent fabric:
Cotton or hemp fabric usually absorbs water immediately. Applying a low-pressure plasma process, the fibre’s surface can be altered to make it repel water. After the treatment, drops run freely over the surface while mechanical properties, the visual appearance, and the permeability for water vapour remain unchanged. The surface modification is limited to a very thin layer. A treatment as short as 2 seconds can be sufficient to achieve this effect in a batch process. Continuous treatments with a speed of more than 20 m/min are conceivable. The stability of the modification can be seen in intermitted washing cycles of fluorocarbon treated cotton fabric. After an initial drop, the finishing remains stable for at least two hours at 95°C. The quality of the repellent effect is evaluated by putting water drops to the fabric surface. A value of 1 means that the drops run freely over the surface and do not penetrate into the material while at a value of 3 the water does not penetrate but it needs vibrations to move the drop. Obviously, this evaluation depends also on the nature of the fabric.

Water repellence of fabric
Figure 7: Water repellence of fabric

4.7. Adhesion improvement in laminates and composites:
In oxygen plasma the number of functional groups at the surface can be increased which can improve the adhesion to other material. The results are stronger laminates and better composite materials.

Adhesion improvement in laminates
Figure 8: Adhesion improvement in laminates

4.8. Flame retardant fabric:
Currently, halogen-containing flame retardants are being banned for ecological reasons. The new kinds of flame-retardant chemistry, e.g. based on organic phosphonate derivatives, are much more expensive. Therefore, their usage should be limited to the absolute minimum. It has been shown that, in the case of plasma-activated fabrics consisting of both natural fibres and polymers, the concentration of flame-retardant chemicals can be reduced considerably without influencing the flame-retardant properties of the treated web. This again leads to considerable cost savings.

4.9. Hydrophobation of nonwovens for filtration applications:
It is mainly plasma polymerisation for coating deposition that has found its way into the filtration industry. A first example of plasma coating can be found in air filter media both for respirator masks and for filters used in HVAC systems. Such filters consist of several layers of meltblown nonwoven PP, which are electrically charged (electrets). Filtration efficiency for oily particles can be greatly improved by applying a hydrophobic/oleophobic coating prior to electrical charging.

Hydrophobation of nonwovens for filtration applications
Figure 9: Hydrophobation of nonwovens for filtration applications

4.10. Hydrophilic coatings on nonwoven PP for battery separators:
NiMhydride rechargeable batteries normally use a nonwoven meltblown PP separator web. In order to improve wetting with the electrolyte, some manufacturers are using gamma rays to increase surface energy, but this is an expensive and even hazardous type of treatment. By applying a permanently hydrophilic type of coating out of gaseous pre-cursors, one can increase wetting behaviour of the battery separator considerably.

For a 1 min wicking of a plasma-coated material, values between 22 and 25 mm were obtained immediately after plasma coating, whereas the uncoated reference material gave 0 mm (no wicking at all). Commercial reference materials on the market, which were not plasma coated, showed wicking values of only 5 to 10 mm. The samples from the wicking test performed 21 days after plasma coating were immersed in a beaker with 30% KOH solution. The beaker was covered with aluminium foil and was then put in an oven at 70ºC for 7 full days. After this, the samples were rinsed in demineralised water and air dried. Then the wicking test was repeated, showing wicking values of 16–18 mm. Wash resistance of permanently hydrophilic coatings is better than for hydrophobic/oleophobic coatings but is still limited to about 7 wash cycles. Again, in the battery separator application, this is not important.

5. Traditional textile processing vs. plasma technology:
Table 3 is showing the advantages of plasma technology over textile wet processing.

Table 3: Traditional textile processing vs. plasma technology:

Plasma processingTraditional wet processing
MediumNo wet chemistry involved. Water-based Treatment by excited gas phaseWater – based
EnergyElectricity – only free electrons heated (<1% of system mass)Heat – entire system mass temperature raised
Reaction typeComplex and multifunctional; many simultaneous processesSimpler, well established
Reaction localityHighly surface specific, no effect on bulk propertiesBulk of the material generally affected
Potential of new processesGreat potential, field in state of rapid developmentVery low; technology
Static
EquipmentExperimental, laboratory and industrial prototypes; rapid industrial developmentsMature, slow evolution
Energy consumptionLowHigh
Water consumptionNegligibleHigh
Handling and storage of bulk chemicalsNoYes
Mixing of chemicals, formulation of bathsNoYes
Raw materials consumptionHighLow
Drying ovens and curing operationsNoYes
Need for solvents, surfactants, acidNoYes
Number of process stepsSingleMultiple
Waste disposal/recycling needsNegligibleHigh
Environmentally costlyNoYes
Innovation potentialVery highModerate

6. Recent Research in Plasma Technology:
In the textile field, significant research work has been going on since the early 1980s in many laboratories across the world dealing with low-pressure plasma treatments of a variety of fibrous materials showing very promising results regarding the improvements in various functional properties in plasma-treated textiles.

Plasma technology is in itself a new research topic in textiles but from all the above discussion it is clear that it has a great potential in textile innovations and there are a lot of things and research has been going on, few of them are listed below.

6.1. Atmospheric pressure plasma vapour treatment of thermo-sensitive poly (N-isopropyl acrylamide):
Poly (N-isopropyl acrylamide) (PNIPAAm) is a new type of smart thermo-sensitive macromolecule material that is characterized by a sudden precipitation on heating, switching from a hydrophilic to a hydrophobic state. By using the self-made equipment of atmospheric pressure plasma vapour treatment running in the environment of argon, PNIPAAm was deposited separately to Polybutylene Terephthalate (PBT) melt-blown nonwovens and Polyester (PET) fabrics. It was found that the wettability and water permeability were signicantly modified by changing the temperature above and below the Lower Critical Solution Temperature (LCST), according to the data derived from measurements of water contact angle, water permeability time and Scanning Electron Microscopy (SEM) images. Considering human body temperature is close to the LCST, these results are valuable for further application to thermo-sensitive textile materials.

6.2. Multifunctional textiles with high UV protection:
Plasma polymerization technique can be used on textiles with TiO2 and/or ZnO nanoparticles and such high UV protective or multifunctional fabrics can be developed.

6.3. Antimicrobial textiles with metallic effects:
Research is going on for developing anti-microbial fabric by Metallization with Ag nanoparticles on textile surfaces by sputtering (PVD) i.e. Physical vapour deposition.

6.4. Atmospheric pressure plasma processing system for angora wool (APPAW):
Recently, FCIPT-Institute for Plasma Research (IPR) and National Institute of Design (NID) carried out a pioneering research work by way of not only developing an innovative Atmospheric Pressure Plasma Processing System for Angora Wool (APPAW) but also successfully installing and establishing it in the Angora Cottage Industry at Kullu.

This plasma plant for surface modification of fibres, generates plasma at atmospheric pressure using air as plasma forming gas. This is a cost-effective green process. Also, it is the first Atmospheric Pressure Plasma System for Textiles developed in the country, for demonstration.

Plasma treatment assists in increasing the friction and cohesion between the fibres. It forms a part of the movement on promotion of non-polluting techniques for mechanical processing of textile materials without any difficulties such as static, shedding, fibrosity. The plasma treatment caused a slight reduction in denier and increase in tenacity of Angora fibre while substantially increasing the friction between the fibres. The plasma treatment to Angora fibres also improves wettability and dye uptake.

7. Conclusion:

  • Plasma is a versatile technology to chemically and physically modify the surface of textile materials.
  • Plasma technology is used to achieve new or improved properties to textile. Plasma is an alternative environmentally friendly technology to complement or substitute several conventional textile processes.
  • Research and development of plasma treatments applied to textiles are still globally increasing. Different studies have been done on natural, artificial and synthetic fibers.
  • Sputtering, etching, chemical functionalization, free-radicals generation and UV radiation are some of the most important effects conferred by plasma treatments to textiles.
  • Plasma technology are increasing their presence in the textile industry for several applications.

8. References:

  1. Yang Chena, Xiaoliang Tang, Baotong Chen a, Gao Qiu, “Atmospheric Pressure Plasma Vapor Treatment of Thermo-sensitive Poly(N-isopropylacrylamide) and Its Application to Textile Materials”, Journal of Fiber Bioengineering & Informatics 4:3 (2011) pp. 285-290.
  2. Shah J.N. and Shah S.R., “Innovative Plasma Technology in Textile Processing: A Step towards Green Environment”, Research Journal of Engineering Sciences, Vol. 2(4), 34-39, April (2013)
  3. http://textilelearner.blogspot.in/2012/04/application-of-plasma-technology-in.html
  4. http://textilelearner.blogspot.in/2013/10/plasma-treatment-in-textiles.html
  5. F. Sadova and E. V. Pankratova, “Low-Temperature Plasma Surface Modification of Textiles Made from Natural Fibers and Advanced Technologies”, Plenary reports from the 5th international symposium on theoretical And applied plasma chemistry, (September 3–8, 2008, Ivanovo, Russia)
  6. Buyle, “Nanoscale finishing of textiles via plasma treatment”, Materials Technology 2009 VOL 24, pp 46-51
  7. R.Shishoo, “Plasma technology for textiles”, The textile institute, Woodhead publishing limited
  8. LEITAT Technological center, “Plasma technology applied to textiles”, T-POT PROJECT 18th June 2009 Terrassa (Spain)
  9. K. Chinta*, S. M. Landage and Sathish Kumar. M, “Plasma technology & Its application in Textile wet Processing”, International Journal of Engineering Research & Technology (IJERT), Vol 1, Issue 22, July 2011
  10. Ms. Anita Desai, “Plasma technology: A review”, The Indian Textile Journal, January 2008 issue.
  11. A newsletter, “Plasma processing update”, Facilitation Centre for Industrial Plasma Technologies, Institute for Plasma Research Issue 56 January – April 2009

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