Since the introduction of plasma technology in the 1960s,the industrial applications of low-pressure and low-temperature plasma weremainly in microelectronic etching. In the 1980s, plasma technology also appliedto other material surface treatment, especially in metals and chemicalpolymers. Due to high restriction in the control of chemical finishing ontextile materials, the new and innovative textile treatments are demanded. In this regard,plasma technology shows distinct merits due to its environmental friendly andbetter treatment results. Presently, research institutions are applying plasmatechnology in textile processing.

 

The plasma is an ionized gas with equal density of positive and negative charges which exist over an extremely wide range of temperature and pressure. The plasma consists of free electrons, ions, radicals UV-radiation and other particles depending upon the gas used. The plasma gas particles etch on the fabric surface in nano scale so as to modify the functional properties of the fabric.

 

Unlike conventional wet processes, which penetrate deeply into fibres, plasma only react with the fabric surface that will not affect the internal structure of the fibres. Plasma technology is to modify the chemical structure as well as the topography of the textile material surface. In conclusion, plasma can modify the surface properties of textile materials, deposit chemical materials (plasma polymerization) to add up functionality, or remove substances (plasma etching) from the textile materials.


Applications

 

There are different methodologies to induce the ionization of plasma gas for textile treatment:


  1. Glow-discharge method- plasma gas is produced at reduced pressure. The methodology applies direct electric current, low frequency over a pair of electrodes.


  1. Corona discharge method - plasma gas is produced at atmospheric pressure by applying a low frequency or pulsed high voltage over an electrode pair.


  1. Dielectric barrier discharge method - plasma gas is produced by applying a pulsed voltage over an electrode pair of which at least one is covered by a dielectric material.


Low-temperature plasma technology including both low glowdischarge under reduced pressure as well as dielectric barrier discharge undernormal pressure have been well established in different industrialapplications. The applications on textiles include desizing of woven fabric,adding functionality and modification of surface properties of textile materials.


The functionality of textile materials can be improved bythe plasma technology such as:


  1. Wettability- there are a lot of investigations on plasma treatment of some textile fibres for changing their wettability properties. For examples, polyester, polypropylene, wool that plasma treatment can improve the ability of these fibres to retain moisture or water droplets on their surface.


  1. Hydrophobic finishing- the treatment of cotton fibre with identified plasma gas such as hexamethyldisiloxane (HMDSO) leads to a smooth surface with increased contact angle of water. The treatment gives strong effect of hydrophobization of treated cotton fibre.


  1. Adhesion- plasma technology can increase adhesion of chemical coating and enhance dye affinity of textile materials.


  1. Product quality- 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.


  1. Functionality- different kinds of plasma gases provide special functionality to textile materials such as UV-protection, anti-bacteria, medical function, bleaching, flame retardancy, etc.


 

Advantages of the plasma technology


  1. It is applicable to most of textile materials for surface treatment.


  1. Optimization of surface properties of textile materials without any alternation of the inherent proper ties of the textile materials.


  1. It is dry textile treatment processing without any expenses on effluent treatment.


  1. It is a green process without generation of chemicals, solvents or harmful substances. The consumption of chemicals is very low due to the physical process.


  1. It is applied for different kinds of textile treatment to generate more novel products to satisfy customer's need and requirement.


  1. It is a simple process which could be easily automated and perfect parameter control.


Machinery for application of the plasma treatment had been well developed in the market. However, the application of plasma technology for different kinds of textile materials has not been fully commercialised in the industry. Local manufacturers may not have both technical and financial capability to conduct applied research and development of such technology for their own production. HKRITA is now working with research partners to develop the plasma technology for textile treatment and finishing.