Surface modification in textiles is gaining popularity. New finishing techniques are being developed by the textile industry to improve the quality of products. The added constraint of developing a piece of fabric under environment friendly conditions is also a rising concern for many manufacturers. Plasma, the fourth state of matter, meets the above requirement, as far as textile wet processing is concerned.
Plasma is a gas with equal densities of positively and negatively charged ions. One peculiar feature of plasma, that makes it a versatile alternative, is that it can exist in extremely vast range of temperature and pressure. With different kinds of treatments, plasma can provide unique surface properties to textiles. Plasma treatment offers a myriad of textile finishes like improved dyeability, printability, colour fastness, adhesiveness, and hydrophobic qualities.
The gaseous state of plasma consists of many excited substances like ions, free electrons, ultra-violet, and infra red radiations. It can be generated by thermal, electrical, mechanical, nuclear, and radiant forms of energy. Based on the particle density, temperature, pressure, presence or absence of electromagnetic fields, the state of the plasma can be distinguished.
Non-thermal plasmas or cold plasmas are widely used in different textile applications. Textile treatments using cold plasma is either done by vacuum pressure or by atmospheric pressure. Plasmas are the most inimitably effective surface treatment tools. The following properties make plasma so unique:
• Plasma is used at low temperature and hence reduces the possibility of damages to the fabric.
• The ability to use plasma at wide thermal, physical, and chemical ranges allow precise tailoring of surface treatments in fabrics.
• The dry treatment processes of plasma make it an environment friendly alternative.
The effect on plasma treatments on fibres and polymers leads to chemical changes, structural changes, and physical changes in the surface layers of fabrics. There are four major effects that are usually observed. One of the effects is always present to some degree, but one may favour the other based on the substrate and the gas chemistry. The following are the four broad surface effects that can be done with plasma in textiles:
Plasma cleaning and etching: It is the removal of impurities or substrate material from the surface of the textile fabrics. Plasma cleaning improves the quality of printing, painting, dyeing, and results in increased adherence of a fabric.
Plasma activation: Introducing new functional groups to the surface of textile is done, for example anti-pilling finishes in wool. Depending on the type of chemical groups used the desired finishes can be obtained.