Plasma Application for Performance Enhancement of Textile Fabric

8/10/2019 Plasma Application for Performance Enhancement of Textile Fabric

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Plasma pplication for Performance Enhancement of Textile Fabric

Plasmais the fourth state of matter,the other three being solid, liquid and gas. A plasmais a hot

ionized gas consisting of approximately equal numbers of positively charged ions and negatively charged

electrons resulting in more or less no overall electric charge. It consists of free electrons, radicals, ions,

UV-radiation, and various highly excited neutral and charged species independent of the gases used. A

gas becomes plasma when the kinetic energy of the gas particles rises to equal the ionisation energy of the

gas.Solar coronas, lightening bolts and nuclear fusion are all examples of plasma. Plasmas also appear in

man-made devices such as fluorescent lamps, neon tubes, welding arcs and gas lasers.

Plasma system classification

Plasma may be classified according to whether they are based on temperature, power source or pressure.

Temperature

Hot plasma

Cold plasma

Power source : AC/DC

Electropositive (EP) plasma/Electeonegative (EN) plasma

Pressure

Low pressure :

Glow discharge plasma

Capacitively coupled plasma (CCP)

Inductively coupled plasma (ICP)

Wave heated plasma

Atmospheric pressure :

Corona discharge plasma

Dielectric barrier discharge (DBD)

One Atmosphere Uniform Glow Discharge Plasma (OAUGDP)

Micro hollow cathode discharge (MHCD) plasma


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(Non-polymerizing) Gasesor mixtures of gases, used for plasma treatment of polymers can include

N2, Ar, O2, He, NH3, H2O, CO2or F.

O2 Hydrophilic, F Hydrophobic(water pepellent, stain repellent)

O2 introduce oxygen containing functional group,

CO2 introduce carboxyl group on the surface,

NH3 introduce nitrogen containing functional group,

Inert gas introduce radical sites on polymer surface (Arsurface roughening)

The main advantages of plasma processing of textiles are

(i) liquid-free dry single-step operation,

(ii) requirement of a minimal amount of chemicals,

(iii) cost-effectiveness in terms of time and temperature,

(iv) imparted functionality independent of substrate chemistry, and

(v) environmental friendliness

Application of plasma in textile processing

Plasma treatment of textiles modifies only the surface of the material without altering the bulk properties

to increase the uptake of dyes and chemicals or to impart a unique functionality or both. Different value-

added functionalities, such as water, stain and oil repellent, hydrophilic, antimicrobial, flame-retardant,

UV-protective, antistatic properties, and improvements in dyeing, printing, biocompatibility, and


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The effectiveness of plasma treatment depends on different factors namely,

1) Nature of gas used

2) Flow rate

3) System pressure

4) Discharge power

5) Duration of treatment

6) Ageing of plasma treated substrate

7)

Temperature change during the plasma treatment

8) Sample distance

Low Pressure Plasma

The advantages of low-pressure plasma processing are:

(i) presence of a high concentration of reactive species,

(ii) uniform glow plasma,

(iii) temperature of plasma below 250 oC, and

(iv) lower breakdown voltages.

However, some of the limitations of low-pressure plasma processing are:

(i) longer processing time,

(ii)

limited sample size to the size of the reactor, and

(iii)

mostly batch processing.

Glow Discharge: It is the oldest type of plasma; it is produced at reduced pressure and assures the highest

possible uniformity and flexibility of any plasma treatment. The methodology applies direct electric

current, low frequency over a pair of electrodes. Alternatively, a vacuum glow discharge can be made by

using microwave (GHz) power supply.

Atmospheric Pressure Plasma

Unlike low-pressure plasma, it is quite challenging to generate plasma at atmospheric pressure due to the

presence of high voltage in a narrow electrode gap and the difficulty in ionizing gaseous molecules and

generation of uniform cold plasma. However, if the stable cold plasma can be generated at atmospheric

pressure, it can overcome the limitations of low-pressure technology. It can also be easily integrated into

existing textile processes for continuous treatment of textiles.


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Corona Discharge: It is formed at atmospheric pressure by applying a low frequency or pulsed high

voltage over an electrode pair. Typically, both electrodes have a large difference in size. The corona

consists of a series of small lightning-type discharges. High local energy levels and problems related to

the homogeneity of the classical corona treatment of textiles make it problematic in many cases.

Dielectric-Barrier Discharge: DBD is produced by applying a pulsed voltage over an electrode pair of

which at least one is covered by a dielectric material. Although lightning- type discharges are created, a

major advantage over corona discharges is the improved textile treatment uniformity.

Plasma chemistry

Different types of interaction of plasma with substrates are discussed below:

(i) Ion formation: Reactions due to the ion formation that would directly lead to a new

chemical product, such as formation of NH3and NO2.

(ii) Recombination: When the rate of producing surface radicals is high and air is

excluded, a tough cross-linked shell is formed that offers protection against solvent

attack.

(iii) Oxidation: In treatment by oxygen containing plasma/UV, surface excitation leads to

the formation of polar groups, such as ketone, hydroxyl, ether, peroxide, and

carboxylic acid that make the surface wettable.

(iv)

Peroxide formation: When a textile is exposed to argon (Ar) plasma followed by

exposure to air, a high proportion of reactive sites is converted to peroxide form.

Because peroxide is known to act as an initiator for vinyl polymerization, it is used

for graft polymerization.

(v) Radical formation: Carbon-free radicals are formed when the energetic ions/ photons

from the plasma/UV break the organic bonds of the polymeric substrate.

(vi) Polymerization: Ionization of an organic monomer in the vapor phase in the plasma

zone leads to a rapid in situ polymerization resulting in formation of thin pinhole-freefilms.

(vii) Surface cleaning: A cleaning process in which argon (Ar), helium (He), and oxygen

(O2) gases are used to ablate organic contaminants such as oil from the substrate

surface.


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Use of plasma in textile processing

Plasma can be adopted to remove polyvinyl alcohol (PVA) based size from the textile

fabrics

Plasma treatment can impart anti-felting, improved dyeability and wetting properties in

wool fiber. It reduces the curling effect by etching off the exocuticle that contains the

disulfide linkages which increase cross linking and contribute towards shrinkage. This

procedure also enhances wettability by etching off the hydrophobic epicuticle and

introducing surface polar groups. (Wool- plasma processing of wool in Israel- 20-25%

increase in dye uptake of wool)

In the synthetic fibers, plasma cause etching of the fiber and introduction of polar groups

leading to dyeability improvement. This has been evaluated through in situ

polymerization of polyester, polyamide and polypropylene fabrics. Plasma-induced

surface modification of micro denier polyester imparted cationic dyeability on polyester

fiber. This technique can lead to a continuous flow system, low energy consumption, and

more environmentally friendly consumption.

Conversion of hydrophobic nylon to hydrophilic upon HeO2plasma treatment

Improving peeling resistance of PE for its application in composites

Limitations of plasma treatment

System dependency is one of the most important disadvantages of the plasma treatment. This

means that the same flow rate, gas pressure and power input may not produce the same level of

the needed reacting species.

Scaling up and converting pilot batch process into a continuous process could also present some

technical challenges.


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Textile materials are made from yarns or directly from fibers. In either case the fibers are

covering each other, especially when they are in high twist yarns. This creates a shadow effect

and the shadowed areas are generally protected from plasma treatment.

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Plasma Application for Performance Enhancement of Textile Fabric