Benefits of atmospheric plasma treatment for textiles

Plasma surface treatments modify the surface properties thereby having a distinct advantage. In this article, Aslam Moolji presents the research results on the use of plasma in textile property modification.

The textile industry is looking out for innovative techniques to improve product quality, new finishing methods which are environment friendly. Plasma surface treatments modify the surface properties thereby having a distinct advantage. There are now large systems for treatment of fabrics and the demand for them is ever increasing. the main effects on textile are 1) The Cleaning Effect 2) Increase of Micro roughness 3) The Production of Radicals to Obtain Hydrophilic Surfaces. Here, we will present the research results on the use of plasma in textile property modification. Treatment on different substrates resulting to improve wetting is also shown. Hydrophilic – Hydrophobic Treatment Dirt Repellent Coatings are also presented.

Introduction
The textile industry has the concerns related to the issues like development and production of raw materials, converting them into finished products, value addition, innovation, human health and environment safety and making profits. Some of these issues resonate with the need of the society like sustainable production systems which are environment friendly and consumer interest. The main concern for production involves innovative recycling technologies for waste treatment. The demand for natural fibres continue to increase for their properties like aesthetics, comfort and biodegradability.
The new frontier now in bio technology for textile processing focuses on surface modification in order to enhance absorption/ dyeing and aesthetic properties. This can be done by Atmospheric Plasma Treatment.

The Plasma Process
It is partially ionised gas composed of highly excited atomic, molecular, ionic and radical species of free electrons and photons. The atmospheric plasma is achieved by the dielectric barrier discharge technology
where it is obtained between electrodes and operate at high frequencies.
The plasma treatment can improve the characteristics like
1) Wettability
2) Flame resistance
3) Adhesive bonding
4) Printability
5) Hydrophobic – hydrophilic
6) Dirt repellent
7) Anti-static properties

Novel application of plasma
Plasma treatment can also contribute to human health and safety by protecting them from exposure to dangerous environment. Protective apparel should have optimum barrier effectiveness and comfort. The effectiveness of the wearer for instance the health worker continues to be a major concern of textile industry because of the risks of infection if the apparel fails. An effective protection in medical application will need reliable adhesive bond strength, which can be achieved by plasma treatment.
Plasma systems can also be used to impart insect control with multifunctional reactive dyes. Wool and speciality hair fibres are readily attacked by cloth moth and larvae. The use of insecticides was banned for these materials. So, plasma treatment is a novel approach where air and water consumption was drastically reduced in comparison to wet chemistry.

Plasma in textile application:
1) Enhances mechanical properties: Softening of cotton and other cellulose based polymers can be achieved with oxygen plasma. The reduction of felt of wool can be also be achieved with the treatment.
2) Electrical properties: Antistatic finish of Rayon with Chloromethyl Dimethylsilane in Plasma
3) Wetting properties: Improvements of surface wetting in synthetic polymers with treatment in air,
O2, NH3 – Plasma.
4) Dyeing and printing: Improvement of capillarity in wool and cotton with treatment in oxygen plasma.
5) Composites and laminates: Good adhesion between layers in laminates depends on the surface characteristics of fibres in layers and the interaction taking place at the interface. The prerequisites condition for good adhesion is surface energy of fibres which can be modified by plasma.

Plasma treatment on plastics
PP is an interesting material for plasma treatment as it’s a hydrophobic material with extreme low surface tension. It is used in large number of technical applications. Improved wettability and adhesion properties are advantageous. Improvement of wetting in PP with Air and NH3 Plasma. Materials such as PTFE which are very difficult to treat by Corona Discharge Technology can be easily treated by Plasma with Air to increase the Dyne Level to 56 Dynes/ Cms2.

In-house treatment setup
We have treated 300 mm PTFE material on our system at 1 mtr/min line speed and 500 Watts and have achieved a Dyne Level of 56 Dynes / Cm2. The Dyne Level was tested using ASTM Std D2578. The treatment remained for over 48 hours and gradually decreased.