Overview on Plasma Finishing Technology

Due to increasing requirements on the finishing of textile fabrics, increasing use of technical textiles with synthetic fibers, as well as the market and society demand for textiles that have been processed by environmentally sound methods, new innovative production techniques are demanded. In this field, the plasma technology shows distinct advantages because it is environmentally friendly, and even surface properties of inert materials can be changed easily.

Plasma technology can be used not only for textile finishing, but also for the optimisation of textile machines, for example, with hard coatings.

It has been known for at least 60 years that plasma could effect desirable changes in the surface properties of materials. However, the practical application of plasma required the development of commercially available, reliable, and large plasma systems. Such systems are now available (mostly in research laboratories) and the application of plasma to industrial problems has been increasing rapidly for the past 10 years

shows possible fields of application of plasma treatments in the textile sector.

Definition of plasma

The physical definition of a "plasma" (glow-discharge) is an ionised gas with an essentially equal density of positive and negative charges. It can exist over an extremely wide range of temperature and pressure. The solar corona, a lightening bolt, a flame and a "neon" sign are all examples of plasma. For the purposes of textile modification the low pressure (0,01 to 1 mbar) plasma, such as found in the "neon" sign or fluorescent lightbulb are used. In the above mentioned applications the desired result is to produce light. However, for the plasma treatment of polymeric substrates, the extremely energetic chemical environment of the plasma is utilised.

Principle of plasma treatment

The plasma atmosphere consists of free electrons, radicals, ions, UV-radiation and a lot of different excited particles in dependence of the used gas. The figure above describes the principle of the plasma treatment. Different reactive species in the plasma chamber interact with the substrate surface. Cleaning, modification or coating occur dependent of the used parameter.

Furthermore, the plasma process can be carried out in different manners. The substrate can be treated directly in the plasma zone. The substrates can be positioned outside the plasma; this process is called remote process. The substrate can be activated in the plasma followed by a subsequent grafting. The substrate can be treated with a polymer solution or gas which will be fixed or polymerised by a subsequent plasma treatment.

How does the plasma treatment act on the textile?

According to requirements the materials to be processed processing (foils, membranes, textiles, polymers,...) will be treated for seconds or some minutes with the plasma. Essentially, four main effects can be obtained depending on the treatment conditions.

1. The cleaning effect is mostly combined with changes in the wettability and the surface texture (see Point 2.). This leads for example to an increase of quality printing, painting, dye-uptake, adhesion an so forth.
2. Increase of microroughness. This effects, for example, an anti-pilling finishing of wool.
3. Generation of radicals. The presence of free radicals induce secondary reactions like cross linking. Furthermore, graft polymerisation can be carried out as well as reaction with oxygen to generate hydrophilic surfaces.
4. Plasma polymerisation. It enables the deposition of solid polymeric materials with desired properties onto the substrates.

The advantage of such a treatment is, that the modification is restricted to the uppermost layers of the substrate, thus not affecting the overall desirable bulk properties of the substrate adherent.

Plasma equipment

The figure below shows a block diagram of a typical plasma system. It consists of 5 modules or functions: vacuum system, power supply, matching network, reactor center, and controller.

• Vacuum system: Low pressure plasma systems operate at 0,1 mbar to 1 mbar with a continuous gas flow into the reactor. In some cases it is necessary to reduce the base pressure in front of the treatment below 0,1 mbar.
• Power supply: This furnishes the electrical power necessary to generate the plasma. The power required ranges from 10 to 5000 watts, depending on the size of the reactor an the desired treatment.
• Plasma reactors have been built utilising a wide range of frequencies, from DC to microwave.
• Controller: It controls all the process variables: type of gas, pressure, gas flow rate, power level, and processing time.

·         Reactor center: This is the "heart" of the plasma system. It can be adapted to the process. The material for processing can be treated as batch, semicontinuous or air-to-air. The last is very expensive due to the necessity of vacuum transfer systems.

• Vacuum system: Low pressure plasma systems operate at 0,1 mbar to 1 mbar with a continuous gas flow into the reactor. In some cases it is necessary to reduce the base pressure in front of the treatment below 0,1 mbar.
• Power supply: This furnishes the electrical power necessary to generate the plasma. The power required ranges from 10 to 5000 watts, depending on the size of the reactor an the desired treatment.
• Plasma reactors have been built utilising a wide range of frequencies, from DC to microwave.
• Controller: It controls all the process variables: type of gas, pressure, gas flow rate, power level, and processing time.

·         Reactor center: This is the "heart" of the plasma system. It can be adapted to the process. The material for processing can be treated as batch, semicontinuous or air-to-air. The last is very expensive due to the necessity of vacuum transfer systems.

Metal-Coated Organic Polymers

Metal-coated organic polymers are used for a variety of applications in many types of industries. If the metallized polymer is to fulfill it's function, it is usually essential that the metal adhere strongly to the polymer substrate. This can be obtained by a plasma pre-treatment of the polymer.

• Example: Oxygen plasma treatment of ABS before copper deposition by evaporation

Composites/Laminates

Good adhesion between fibers and matrix (or laminates) depends upon the surface characteristics of fibres, matrix and the physico-chemical interactions taking place at the interface. A prerequisite condition of good adhesion between fibre and matrix remains the surface energy of fibers which must be higher or equal to the surface energy of the matrix. This can be achieved with plasma treatments.

Outlook

The textile industry have to fullfill a lot of partly new technological requirements which have an impact to European and American markets. The following examples belong hereto.

• increasing environmental awareness
• demands on safety of the production process and working place
• increasing requirements as to the performance of the products
• aspiration for personal safety and comfort
• rising price pressure and increasing energy and raw material costs
• decrease of unit costs and at the same time improved quality
• tailor made products

Here it is necessary to recognise chances and risks. New markets and additional sales potential can be found where products specifically respond to these trends. The greatest challenge has been and still is, the development and use of new technologies, for example, the plasma technology to achieve a better price-to-performance ratio. This calls for two options: First of all a broadening and a deepening of the knowledge about possibilities and chances of the plasma technology. Secondly, a strong partnership between research centres, developer of plasma-based plants, and companies from the textile sector. Both are certainly not totally new ideas, but we very often lack the understanding of the necessity which is prerequisite for success.

I think, that this symposium gives a lot of information concerning the plasma modification of polymeric materials, together with the possibilities and limits of these innovative technique.

Further i will discuss more about innovation in textile. You can visite my another site HERE

Plasma finishing technology for Swiss knit fabrics

13 July 2010, Buhler - Swiss knit fabrics manufacturer Eschler and Austrian textile finishing specialist Grabher Group, have joined forces to engineer a new generation of functional fabrics for sports and workwear using cutting edge plasma finishing technology.

Plasma, known as the fourth state of matter, is created by applying electrical fields to pure gas or gas mixtures in a vacuum chamber. The gas is then ionized and leads to a chemical reaction on the surface of the respective material. From a textile perspective, the right combination of gas mixture composition, frequencies and gas flow, results in the systematic surface modification of fabrics. Durable effects such as hydrophilicity, hydrophobicity and dirt repellency are achievable.
Until now, the standard for textile finishing has been wet chemical processes where the desired effects are usually achieved by the use of additives or coatings. However, these treatments often interfere with key textile properties such as flexibility, strength and handle and permanency can be limited due to mechanical abrasion and low wash resistance.
The combination of different properties can also be restricted and plasma technology aims to avoid these disadvantages.It works exclusively with a so-called ‘dry process’, which it says is extremely eco-friendly and uses a minimum of water and chemicals, saves energy and is free of fluorocarbon compounds (PFOA or PFOS).

The new technology allows a great eco balance that no other treatment gets even close to. The new high-tech fabrics are ideal for a broad range of sports depending on the plasma treatment: cycling, triathlon, running, functional underwear cross-country and alpine skiing, trekking and mountaineering. The first apparel pieces will be available for end consumers in summer 2012.”

........further i will discuss about it's principle and mechanism.

Waterless dyeing process for DryDye fabrics

17 August 2010, Bankok - The Yeh Group, a leading producer of functional knitted fabrics has announced plans to introduce DryDye fabrics which use an exclusive waterless dyeing process that the company says will save it millions of litres of fresh water annually. The announcement came at the recent OutDoor Show in Friedrichshafen, Germany and the Outdoor Retailer Show in Salt Lake City, Utah.

Water scarcity and increased environmental awareness are world-wide concerns which are causing a sharp rise in prices for intake and disposal of water. The textiles industry is also one of the biggest consumers of water with conventional textile dyeing using large amounts of fresh water which is disposed of as waste water containing dyestuff chemicals. The Yeh Group says that in its experience, an estimated 100-150 litres of water are needed to process 1 kg of textile material. Water is also used as a solvent in many pre-treatment and finishing processes, such as washing, scouring, bleaching, dyeing, rinsing and finishing and the contaminated water must then be handled and treated prior to disposal or recycling.

DryDye fabrics

The Yeh Group, which produces both warp and weft knitted fabrics, says it will be the first textile manufacturer to implement a new waterless dyeing process developed by DyeCoo Textile Systems of the Netherlands which is currently being readied for commercial introduction in the fourth quarter of this year. The company says it has exclusive rights to the process and is branding fabrics produced using it, as DryDye fabrics. 

Supercritical fluid CO2

“Elimination of the water process and chemicals is a real and significant breakthrough for the textile dyeing industry. This new process utilizes supercritical fluid carbon dioxide (CO2) for dyeing textile-materials. It is a completely waterless dyeing process using only nominal amounts of CO2, nearly all of which is recycled. DryDye fabrics dyed with this unique waterless process will have the same dye qualities and durability as current, conventionally-dyed fabrics,” a spokesperson for the Yeh Group said.

The Yeh Group, which claims to be an innovative, environmentally responsible producer of quality knit fabrics and garments, supplies to premium brands in sports and intimate apparel markets. By pioneering and implementing this new waterless dyeing process, the company says it will eliminate the use of millions of litres of fresh water in dyeing fabrics using the new process.

Instead of current aqueous dyeing systems, DryDye fabrics will be dyed using supercritical carbon dioxide in a stainless steel chamber developed and tested by DyeCoo. Yeh Group says, for the past three decades, supercritical fluids have been used in various extraction processes, including the extraction of natural substances for the production of pharmaceuticals, cosmetics and spices.  In addition, leading producers of textiles dyestuffs have attempted to harness the technology for textiles dyeing but none has produced a successful commercial system to date.

Supercritical fluid CO2 is said to have become a mainstay in extraction processes in the food industry (decaffeination, extraction of hops) and apparel dry cleaning, where it is said to be the best, gentlest, most thorough cleaning method now available. Carbon dioxide is also said to be considered the best supercritical fluid for the dyeing process, is naturally occurring, chemically inert, physiologically compatible, relatively inexpensive and readily available. 

Dyeing polyester and other synthetics

“Using supercritical fluid CO2, polyester and other synthetics can be dyed with modified disperse dyes.  The supercritical fluid CO2 causes the polymer fibre to swell allowing the disperse dye to easily diffuse within the polymer, penetrating the pore and capillary structure of the fibres.  The viscosity of the dye solution is lower, making the circulation of the dye solutions easier and less energy intensive.  This deep penetration provides effective colouration of polymers which are characteristically hydrophobic.  Dyeing and removing excess dye are processes that are done in the same vessel.  Residue dye is minimal and may be extracted and recycled,” the Yeh Group says.

Reductions in operating costs

According to the Yeh Group, supercritical CO2 dyeing gives excellent results as far as dye levelness and shade development are concerned. The physical properties of dyed yarns are also said to be equivalent to conventional methods.   Conventional textile dyeing is very water and energy intensive in pre-treatment, dyeing, and post-treatment (drying).  The supercritical CO2 process however, is said to use less energy than conventional processes, resulting in a potential reduction in operating costs of up to 50%. The company says the only overlap is in the pre-treatment process, which is essentially the same for both.

Availability

DryDye fabrics will be available to consumers in early-2011 through selected brand customers of the Yeh Group and the initial brands adopting and marketing DryDye fabrics will be announced in the coming weeks. The Yeh Group was established in 1988 and is located on a 40 acre site near to the city of Bangkok in Thailand where it specializes in performance polyester knit fabrics. The group is composed of Tong Siang and Penn Asia and has sales offices located in Europe and North America. Current customers include Adidas, The North Face, Puma, Mammut, Odlo, Mizuno and Victoria Secret. DyeCoo Textile Systems B.V. is based in the Netherlands and claims to be the world's first supplier of industrial CO2 dyeing equipment, for which it holds patents. The company also offers its own range of dyes for CO2 dyeing.

Tea fibre

Tea fiber is a kind of new fiber developed by Qingdao Meidu Textile Co., Ltd.. It is high-end functional fiber firstly developed at home and abroad, and reaches the international advanced level. It is antibacterial and odor resistant viscose fiber made from natural tea pigment, tea polyphenols and catechins which are extracted from tea.

Tea fiber is natually antibacterial, odor resistant, moisture absorption and breathable. The bacteriostasis rate and bactericidal rate on staphylococcus aureus and escherichia coli have reached or exceeded the standard of China, US and Japan.

The natural green tea antimicrobial agent uniformly distributes in the tea fiber, thus it can improve the microcirculation of human body after the long-term contact with skin. The textile products made by the fiber are anti-radiation and anti-ultraviolet.

Tea fiber and its products are naturally toasted almond colored, which will not cause pollution and are harmless to human body.

Tea fiber is believed to have a bright future.