Министерство образования Республики Беларусь

Учреждение образования

"Белорусский государственный университет транспорта"

Кафедра "Иностранные языки"

Реферат "Плазменные технологии "

Выполнил	Проверил
Панков Р.И.	Коммисарук В.И.

Гомель, 2011

Contents

1.Articles……………………………………………………………………………….….3

1.1 Plasma technology………………………………………………………….…3

1.2 Plasma-Detonation Technology for Modification of the Surface Layer of

metal parts………………………………………………………………………….16

1.2.1 Introduction………………………………………………………....16

1.2.2 Test method ……………………………………………………..…..17

1.2.3 Structuring of the surface layer………………………………….…..18

1.2.4 Conclusions………………………………………………………….21

2.Summary of the articles……………………………………………………………….…23

2.1 Plasma technology………………………………………………………….….23

2.2 Plasma surface ………………………………………………………………...27

THE TERMINOLOGICAL DICTIONARY ON A SPECIALITY…………………….…28

List of literature…………………………………………………………………..37

1.Articles

1.1 Plasma technology.

Lower cost of operation, improved durability and wear and development of new attributes for textiles are the key benefits that plasma based manufacturing of textile can bring, affirm Anita A Desai.

One of mankind's first industries was textile manufacturing. Ancient people used the primitive processing technologies available at the time: spinning, weaving, washing and treatment with caustic to remove oils, dirt and residue generally by hand. With the industrial revolution came automated treatment method and use of flowing rivers to drive machinery. Processing became faster. Processor could handle more products and achieve better reproducibility than they could with the hand driven machines. Later as steam power replaced water power, looms became faster. That drove the need for sizing added to the yarn. Electric lighting enabled the mills to work through the night.

As many do today. new chemical treatment for bleaching, dyeing and mercerising provided better strength, less shrinkage, bright colours and whiter cottons. At higher production rate and longer production hours, mills could produce more finished fabric than ever before and with greater consumer appeal. The changing technology, from hand power, to water power to steam and then to electricity, fundamentally changed the textile industry, its product marketability and its profitability. Now its time for yet another change! Plasma technology is poised to change the concept of textile wet processing.

Textile manufacturing was once considered a regional or national industry. Today it is clearly international. With many key processing patents expired and production methods well known, the same product can be made in India, China, United States and Europe. With commodity products the textile industry competes for the consumer's attention on the basis of product quality, price and defining attribute.

The cost of manufacturing is a key concern and is driven by consumable currency conversions. These cost factors vary by location. If the technology is same everywhere, then the region with lowest cost factor will have the lowest cost of production and can therefore under-price everyone else. But what if the technology is not the same? What if a new technology changes the cost structure of textile industries by reducing the energy consumption, environmental waste and using fewer chemicals? This is the cost benefit that plasma based technology can offer the textile industry.

History has also shown that consumer will pay more for clothing with a defining and desirable attribute. The development of wash and wear clothing, later followed by permanent press finishes demonstrated this. The second significant benefit that plasma based textile manufacturing offer is development of new fabric treatment with a desired attribute that can not be achieved by other means.

Plasma modification of textiles saves large quantity of water, chemicals and electrical energy, which is made possible since the plasma process does not produce large volume of waste or toxic by-products. Over the past decade there has been rapid exploration and commercialisation of plasma technology to improve the surface properties of textile material without changing the bulk properties. Modification of textile surface by plasma treatment offers a lot of benefits and overcomes the draw back of the classical wet chemical finishing. A major advantage of plasma surface treatment is the lack of harmful by product from the treatment process.

What is plasma?

Irving Langmuir first used the term plasma in 1926 to describe the inner region of an electrical discharge. Later, the definition was broadened to define a state of matter in which a significant number of atom and/or molecules are electrically charged or ionised. The components present will include ions, free electrons, photons, neutral atoms and molecules in ground and excited states and there is a high likelihood of surface interaction with organic substrates. In order to maintain a steady state, it is necessary to apply an electric field to the gas plasma, which is generated in a chamber at low pressure. (Kan, 1999; Ganapathy, 2000; Pane, et al 2001; Allan, et al 2002).

Plasma, as a very reactive material, can be used to modify the surface of a certain substrate (typically known as plasma activation or plasma modification), depositing chemical materials (plasma polymerisation or plasma grafting) to impart some desired properties, removing substances (plasma cleaning or plasma etching), which were previously deposited on the substrate (Pane, et al 2001).

Plasma is any substance (usually a gas) whose atoms have one or more electrons detached and therefore become ionised. The detached electrons remain, however, in the gas volume that in an overall sense remains electrically neutral. Thus, any ionised gas that is composed of nearly equal numbers of negative and positive ions is called plasma. The ionisation can be effected by the introduction of large concentrations of energy, such as bombardment with fast external electrons, irradiation with laser light, or by heating the gas to very high temperatures.

A gas becomes plasma when the kinetic energy of the gas particles rises to equal the ionisation energy of the gas. When this level is reached, collisions of the gas particles cause a rapid cascading ionisation, resulting in plasma. If the necessary energy is provided by heat, the threshold temperature is from 50,000 to 1,00,000 K and the temperatures for maintaining a plasma range up to hundreds of millions of degrees. Another way of changing a gas into plasma is to pass high-energy electrons through the gas. The individually charged plasma particles respond to electric and magnetic fields and can therefore be manipulated and contained. The atmospheres of most stars, the gas within the glass tubing of neon advertising signs, and the gases of the upper atmosphere of the earth are examples of plasmas. On the earth, plasmas occur naturally in the form of lightning bolts and in parts of flames.

There are many different ways to induce the ionisation of gases. (1) Glow discharge, (2) Corona discharge, (3) Dielectric Barrier discharge.

Different forms of plasma Artificially produced plasma Terrestrial plasmas Space & astrophysical plasma Those found in plasma display.Inside fluorescent lamps, neon signs etc.

Rocket exhaust.The area in front of space craft's heat shield during reentry into the atmosphere.Fusion energy research.The electric arc in an arc lamp, an arc welder or plasma torch.

Plasma used for surface modification of textiles etc. Lighting.Ball lighting.St. Elmo's fire.Sprites, elves, jets.The ionosphere sun and other stars

(Which are plasmas heated by nuclear fusion). Where, ni is the number density of ions and na is the number density of neutral atoms. The amount, or degree, of ionisation is called the "Plasma density".

Generally, high plasma densities are desirable, because electrons impact gas molecules and create the excited-state species used for textile treatment. Having more electrons generally equates to faster treatment time. However, very high plasma densities (greater than 1013 electrons cm-3) can only exist with very high gas temperature. This extremely high level of plasma density is unsuitable for textile treatment, because the plasma's energy will burn almost any material. These plasmas, often called thermal plasmas, are used for incineration.

Plasma properties are dependent on the plasma parameters like degree of ionization, the plasma temperature, the density and the magnetic field in the plasma region. Different range of plasma depending on density and temperature is shown as below:

Principle of plasma processing

Plasma technology is a surface-sensitive method that allows selective modification in the nm-range. By introducing energy into a gas, quasi-neutral plasma can be generated consisting of neutral particles, electrically charged particles and highly reactive radicals. If a textile to be functionalised is placed in a reaction chamber with any gas and the plasma is then ignited, the generated particles interact with the surface of the textile. In this way the surface is specifically structured, chemically functionalised or even coated with nm-thin film depending on the type of gas and control of the process.

Principle of plasma processing can be shown as below:

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

Plasma treatments have been used to induce both surface modifications and bulk property enhancements of textile materials, resulting in improvements to textile products ranging from conventional fabrics to advanced composites. These treatments have been shown to enhance dyeing rates of polymers, to improve colourfastness and wash resistance of fabrics, to increase adhesion of coatings, and to modify the wet-ability of fibres and fabrics. Research has shown that improvements in toughness, tenacity, and shrink resistance can be achieved by subjecting various thermoplastic fibres to a plasma atmosphere. Recently, plasma treatments have produced increased moisture absorption in fibres, altered degradation rates of biomedical materials (such as sutures), and deposition of low friction coatings.

Unlike wet processes, which penetrate deep into the fibres, plasma produces no more than a surface reaction, the properties it gives the material being limited to a surface layer of around 100 angstroms. These properties are very varied and can be applied to both natural fibres and polymers, as well as to non-woven fabrics, without having any effect on their internal structures. For example, plasma processing makes it possible to impart hydrophilic or hydrophobic properties to the surface of a textile, or reduce its inflammability. And while it is difficult to dye synthetic fabrics, the use of reactive polar functions results in improved pigment fixation. Also, with plasma containing fluorine, which is used mainly to treat textiles for medical use, it is possible to optimise biocompatibility and haemocompatibility - essential for medical implants containing textiles.

The following table shows various applications of plasma in textiles:

Various application of plasma in textile. APPLICATION MATERIAL TREATMENT Hydrophilic finish PP, PET, PE Oxygen plasma, Air plasma Hydrophobic finish Cotton, P-C blend Siloxane plasma

Antistatic finish Rayon, PET Plasma consisting of dimethyl silane

Reduced felting Wool Oxygen plasma

Crease resistance Wool, cotton Nitrogen plasma

Improved capillarity Wool, cotton Oxygen plasma

Improved dyeing PET SiCl4 plasma

Improved depth of shed Polyamide Air plasma

Bleaching Wool Oxygen plasma

UV protection Cotton/PET HMDSO plasma

Flame retardancy PAN, Cotton, Rayon Plasma containing phosphorus

Plasma technology in textile

Various plasma technologies used in textile

There are many different ways to induce the ionisation of gases. (1) Glow discharge, (2) Corona discharge, (3) Dielectric Barrier discharge, (4) Atmospheric pressure plasma technique.

Glow Discharge:

It is the oldest type of plasma technique. It is produced at reduced pressure (low-pressure plasma technique) and provides the highest possible uniformity and flexibility of any plasma treatment. The plasma is formed by applying a DC, low frequency (50 Hz) or radio frequency (40 kHz, 13.56 MHz) voltage over a pair or a series of electrodes. (Figure A, B, C) Alternatively, a vacuum glow discharge can be made by using microwave (GHz) power supply.

Corona Discharge:

It is formed at atmospheric pressure by applying a low frequency or pulsed high voltage over an electrode pair, the configuration of which can be one of many types. Typically, both electrodes have a large difference in size (Figure shown below). The corona consists of a series of small lightning-type discharges; their in homogeneity and the high local energy levels make the classical corona treatment of textiles problematic in many cases.

Dielectric-Barrier Discharge:

DBD is formed by applying a pulsed voltage over an electrode pair of which at least one is covered by a dielectric material (Figure shown below). Though also here lightning-type discharges are created, a major advantage over corona discharges is the improved textile treatment uniformity.

Atmospheric pressure plasma technique:

As discussed earlier, there are various forms of plasma depending on the range of temperature and electron density. Generally, high plasma densities are desirable, because electrons impact gas molecules and create the excited-state species used for textile treatment. Having more electrons generally equates to faster treatment time. However, very high plasma densities (greater than 1013 electrons cm-3) can only exist with very high gas temperature (Thermal Plasma). This extremely high level of plasma density is unsuitable for textile treatment, because the plasma's energy will burn almost any material. Hence for textile processing, the plasma needs to do their job at room temperature, thus the name 'cold plasma'.

This is due to the fact that the energy of the plasma is mainly confined to the energy of low mass electrons. Non-thermal plasma or cold plasma is characterised by a large difference in the temperature of the electrons relative to the ions and neutrals. Thus, Te >> Ti � Tn. As the electrons are extremely light, they move quickly and have almost no heat capacity. Ionisation is maintained by the impact of electrons with neutral species. These plasmas are maintained by passing electrical current through a gas. The low temperature makes them suitable for textile processing. However, non-thermal plasmas generally require low-pressure or vacuum conditions.

Despite all the significant benefits, plasma processing has failed to make an impact in the textile sector because of a particular constraint, which is incompatible with industrial mass production. All the technologies developed to date are based on the properties of low-pressure plasmas. The process must take place in an expensive, closed-perimeter vacuum system and cannot be used for continuous production lines operating at room temperature, with machines processing fabric 2 metres wide at high speed.

To overcome these restraints, Atmospheric Pressure Plasma Techniques are being developed. This technique provides the highest possible plasma density (in the range of 1 to 5 x 1012 electrons cm-3), without the associated high gas temperatures and the cold plasma chemically treats fabric and other substrates without subjecting them to damaging high temperatures. The Atmospheric Pressure Plasma is a unique, non-thermal, glow-discharge plasma operating at atmospheric pressure. The discharge uses a high-flow feed-gas consisting primarily of an inert carrier gas, like He, and small amount of additive to be activated, such as O2, H2O or CF4.

Sources for Atmospheric Pressure Plasma

Various Atmospheric Pressure Plasma sources are as follows:

Dielectric-Barrier Discharge:

It uses a dielectric covering over one or both the electrodes, of which one is typically low-frequency RF or AC driven, while the other is grounded. The purpose of dielectric film is to restrict and rapidly terminate the arcs that form in the potential field between the two electrodes. The discharge consists of a multitude of rapidly forming and rapidly terminated arcs that fill the volume between the electrodes. Material can be processed using the ozone generated (using oxygen feed-gas) or by passing the dielectric substrate between the electrodes.

Corona Discharge:

It is non-arcing, non-uniform plasma that ignites the region of the high electric field generated by the sharp points of the electrodes. To prevent arcing, no grounded surface is near these field emission points. Thus the discharge is non-uniform and the plasma density drops off rapidly with increasing distance from the electrode.

Plasma Torch:

The DC plasma torch is thermal plasma characterised by a high ion temperature/ electron temperature. This source makes use of its very high gas temperatures for materials processing applications. RF plasma torch are also used which have inductive coupling. However, plasma torch are rarely used for textiles.

Atmospheric Pressure Plasma Jet:

Atmospheric Pressure Plasma Jet (APPJ) is similar to the plasma torch in some respects, but is non-thermal plasma and shows vast difference in ion and electron temperatures. APPJ produce a stable, homogenous and uniform discharge at atmospheric pressure using 13.56 MHz RF power and a predominate fraction of helium (He) feed-gas. APPJ operates without any dielectric electrode cover, yet is free of filaments, streamers and arcing. The gas temperature of the discharge is typically between 50 and 300oC.

Atmospheric Pressure Plasma Jet is the most promising technique among all Atmospheric Pressure Plasma Techniques and is widely used for textile processing. Here, helium feed-gas (about 99 %) mixed with a small amount of reactive gas (typically 1-3 % oxygen) enters the annular volume formed between RF powered electrode and the outer, grounded metal tube. One novel aspect of APPJ is that the discharge is formed in this small volume, which has insufficient room for the immersion of the substrate. However, the active chemical species formed by the plasma, rapidly exit the source and impinge downstream on the work-piece. In this way, the substrate is mostly exposed to active neutrals and radicals, rather than ions. The absence of ion chemistry in the downstream flow increases chemical selectivity and reduces surface damage

Experimental set-up

A schematic diagram of the plasma configuration can be seen in figure (a). Two circular copper electrodes (diameter = 7 cm) are placed within a cylindrical enclosure. Both electrodes are covered with a glass plate (thickness = 2 mm) and the inter electrode distance is 8 mm. The upper electrode is connected to an ac power source (frequency 50 kHz). The lower electrode is fixed and connected to the earth. The discharge current is obtained by measuring the voltage over a small resistor R (100_), inserted into the current loop. The voltage is measured using a high voltage probe (Tektronix P6015A). The current and voltage waveforms are recorded using an oscilloscope (Tektronix TDS210-60 MHz) connected to a computer.

The total power fed into the electrical circuit is kept constant at 15W. At the top of the cylindrical enclosure, air (Air Liquid-Alphagaz 1) is fed into the system at 0.5 l min-1. The gas outlet is connected to a rotary vane pump and the pressure in the plasma chamber is kept constant by using valves. Plasma treatment is then carried out in the medium pressure range (0.3-7 kPa) and for different treatment times ranging from 0 to 10 s. During the experiments three layers of 100% polyester are placed on the lower glass plate. Each layer is labelled.

In the Figure (b), the hydrophilicity induced by plasma treatment of the different non-woven layers is evaluated using a horizontal wicking experiment. A needle which provides a continuous supply of distilled water at a rate of 1.9 ml min-1 makes contact with the test specimen. The water is absorbed by the fabric to form a wetted spot, and the area of the spot after 15s of water supply (A15s) is assumed as a measure of the hydrophilisation effect. A picture of the wetted area A15s is taken with a digital camera and analysed by image processing software.

The whole procedure shows standard deviations between 2% and 15%. No difference is found between the hydrophilicity of the upper and lower side of the non-woven layers. To characterise the behaviour of gaseous discharges so-called 'Lichtenberg figures', named after their discoverer are regularly used. A photographic film (Repro N5) is used as a light sensitive medium. The spectral sensitivity is such that the films filter out the UV radiation and register almost solely the visible light from the micro discharges as described in. Experiments are carried out in a dark room. The photographic film is placed on the lower electrode under the three textile layers and removed after 5 min of plasma burning.

Effect of plasma treatment on different fabric surface

(A) Plasma treatment for cotton:

It has been reported in literature that plasma treatment improves the wet-ability of grey cotton fabric by water and caustic soda solution. In another work cotton has been treated with radio frequency plasma in air at different power levels and time intervals. From the literature it has been seen that the plasma treatment can lower the moisture content and decrease surface resistivity. In some studies plasma initiated grafting of cotton has also been carried out. As in the case of wool, the specific surface area of cotton after oxygen plasma treatment is increased. On the other hand, the treatment with a hexamethyldisiloxane (HMDSO) plasma leads to a smooth surface with increased contact angle of water (sessile drop method) up to a maximum of 130°. Thus, a strong effect of hydrophobisation is achieved. Similarly, when a hexafluoroethane plasma is used instead of an HMDSO plasma the surface composition of the fibres clearly indicates the presence of fluorine and the material becomes highly hydrophobic. Still, the water vapour transmission is not influenced by the hydrophobisation. Hydrophobisation in conjunction with increased specific surface area results in an effect generally known as Lotus effect: dirt particles are easily removed from the surface by water droplets (Figure 3).

(B) Plasma treatment for wool and silk:

Lower temperature plasma treatment of wool has emerged as one of the environmental friendly surface modification method for wool substrate. The efficiency of the low temperature plasma treatment is govern by several operational parameters like

Nature of the gas used

System pressure

Discharge power

Duration of treatment

Plasma treatment can impart anti-felting effect degreasing, improved dyestuff absorption and increasing wetting properties. Other changes in wool properties are as follows

Plasma treatment increases fibre-fibre friction but reduces the differential friction effect.

Plasma treatment does not change the strength and the elongation, the breaking force in loop form is slightly reduce.

The fatty matter content in wool is reduced by about 1/3 due to plasma treatment.

The water content of the wool top is reduced by about 3% due to plasma treatment. Plasma treatment considerably reduces the felting potential for any product obtains from the modified wool. The reduction in the content of covalently bound highly hydrophobic methylicosanoic acid and increases the content of oxidised sulfur spaces are the main factors responsible for improvements in dyeing and shrink proofing of plasma treated wool.

Silicon resins applied to plasma treated wool increase the shrinkage over that for untreated wool. The polymer after treatment reduces both relaxation and felting shrinkage almost independently of plasma treatment time. There is more even and quicker penetration of dyestuff and chemicals in plasma treated wool than the untreated reference sample. Surface analysis of wool fibres treated with different plasma gases reveals that the wettability, weakbilty, surface contact angle of the material are significantly changed in a direction that may lead to new uses for these materials. Plasma treatment increases the hydrophilic groups in the wool fibres and the cystine linkages present in the surface layer are converted to cystic acid. The endocuticle and the density of crosslink in the surface layer are decreased by the reactive spaces in the plasma gas and thus facilitate diffusion of dyes and chemicals.

Plasma treated wool may exhibits more or less firm or harsh handle because of surface roughing. This property is very important for hand knitting yarns or yarns for underwear fabrics. The enzyme treatment is capable of improving the handle of plasma treated wool. Incase of silk fibre the N2 plasma pretreatment can increase its wettability.

Low temperature plasma (LTP) is regarded as an emerging technique when used to achieve the effect of an anti-felt finishing in wool. Cuticle cells of the wool fibres treated with air plasma show a surface similar to that of the UT wool, although the roughness of the surface seems to have slightly increased due to the presence of micro craters N2 plasma treated fibres show higher advancing contact angle values than air plasma treated fibres, suggesting a minor presence of hydrophilic groups on the surface of the N2 plasma treated fibre.

That point confirms that at the treatment times studied, the main effect of air and N2 LTP is superficial chemical modification. water vapour plasma produces an important increase in the hydrophilicity of the fibre. Oxygen plasma reveals as the most aggressive of the plasma gases studied, in terms of etching at shorter times. Scanning electron microscopy (SEM) can be used as a tool for the study of the topographical surface effects of plasma on fibres. (Figure a).

LTP treatment could influence not only the mechanical properties but also affect the air permeability and thermal properties of the wool fabrics (Figure b).

Chen 1996 studied the free radical formation on cotton and wool fibres treated with low Temperature plasmas of O2, N2, Ar, CO, CF4 at the RF generator, at the power of 300W and the pressures of 0.3-1.5 Torr. Free radicals play an important role in polymerisation, grafting, cross-linking and implantation. Table 3 shows that free radical intensities are different for various gases with the general rule that O2<N2<Ar<H2<CO<CF4 (Chen,1996). The free radical formation was increased with increasing time.

If the disadvantages of plasma treatments, such as the high cost of the plasma device, can be eliminated, this technology will be valid and very important method for the textile finishing industry.

Plasma may be used for removing the contaminants, finishing and sizing agents from the fabric. Desizing of polyester fabric that used polyvinyl alcohol as the sizing agents can be removed by plasma treatment. The wet-ability of polyester fabric also increases significantly. Polyester fibre can be effectively modified by low pressure plasma treatment. Treatment of polyester fibre by glow discharge in air or oxygen causes a partial degradation of the fibre surface together with an increase in the capillary sorption of Iodine or cation in aqueous solution. Wetting out properties of polyester can be achieved by treatment of polyester with plasma and corona discharge. The fabric can be processed without the use of wetting out agents.

Generally polyester has a very hydrophobic surface because the surface is Made up of ether oxygen (C-O-C) linkages while the hydrophilic ester oxygen (C=O) is facing towards the core of the fibre. When surface is treated by plasma either the ester oxygen causes closer to the surface as a result of etching or some new C=O bonds are forms due to oxygen ions present in the plasma chamber.

A small scale matched for the preparation of liner fabric is described, which practically eliminates the use of chemical reagents. The grey fabric is treated in a glow discharge plasma in air and then the process maintains the strength of the fabric. Maintaining the strength of the fabric does not affect the natural colour of liner and does give fabric a high degree of hydrophilicity.

The barrier discharge or corona treatment of polypropylene significantly increases the hydrophilicity of the surface, the contact angle of water being decreased from 90° to 55°. Even after two weeks a sustained effect is observed, the contact angle of water being 60°. Instead of the contact angle of water, the oxygen/carbon ratio of the atomic composition of the surface can be used to follow the influence of a plasma treatment, in particular for polypropylene fleeces with layered-structure.

The oxygen/carbon ratio for the first layer is highest; but even at the tenth layer a significant effect is observed. The uptake of oxygen at a polypropylene surface is even more significantly demonstrated when maleic acid anhydride (MAH) is used as an assisting reagent. The incorporation of oxygen is permanent and a contact angle with water of 42° can be achieved (Figure 4). When polyethyleneterephthalate (PET) fibres are used as an enforcing material for a polyethylene (PE) matrix, the hydrophobisation of the PET fibres using an ethylene plasma is quite impressive since the adhesion strength can be increased from 1 to 2.5 N/mm. The fracture morphology of these composite materials clearly shows the tight adhesion of the matrix to the fibre.

Permanent hydrophilisation of PP by plasma-induced grafting of MAH

R&D results (Carried out by Europlasma)

Treatment of wool:

Plasma treatment of wool has already been examined by several research institutes. In general similar results are reported although the intensity of the obtained effect might differ from case to case. For our trials a knitted wool fabric, without special pre treatment was used. Plasma treatment was performed in a plasma chamber of ± 1mі, using secondary plasma generated with a 40 kHz plasma generator with a plasma power between 2,000 and 3,500 watt. Treatment times were varied between 1 and 7 minutes. The most important effects observed during our evaluations are:

Improvement in wettability with a factor 100 to 1,000 The original fabric is very hydrophobic, after treatment a water drop is taken up within one to two seconds.

No significant change in mechanical properties of individual fibres.

Important change in mechanical properties of the yarns.

Increase in yarn tenacity with up to 50 %.

Increase in yarn elongation at break up to 250 % (depending of the original value before plasma treatment).

Improved anti-felting character and shrink resistance during laundering. The original surface shrinkage of 57 % (according TM 31) can be reduced below 10% after plasma treatment, offering "Super-wash" quality to the treated fabric.

Regarding the origin of the improved anti-felting behaviour, contradictive explanations are proposed. According to us the anti-felting behaviour is due to an increase in fibre/fibre friction. This reduces the slipping of the fibres one to another that causes the shrinkage and felting of the wool material. The increased friction offers also an explanation for the increased yarn tenacity and elongation at break. It was indeed shown that fibre/fibre friction can be increased with more than 50 % after plasma treatment of wool sliver.

Treatment of cotton:

Similar effects can be observed after treatment of cotton fabrics or yarns in oxygen plasma. In general the effects such as improved wet-ability, increased strength or fibre/fibre friction are less pronounced if compared to wool materials. Much depends upon the level of pre treatment already applied to the material. For instance regarding wet-ability the improvements are not significant if the plasma treatment is applied to a full bleached cotton. If intensive oxygen plasma treatments are applied to cotton fabric also negative effects can be observed namely a reduced tear and abrasion resistance. The negative impact can be minimised by selecting appropriate treatment conditions.

Treatment of PP:

PP is a very interesting material for plasma treatment. PP is a very hydrophobic material with extreme low surface tension. On the other hand PP is used in a large number of technical applications were an improved wet-ability or adhesion properties are advantageous. This is also the case for PP technical textile applications such as filters, medical or hygiene applications. By using oxidative plasma important improvements in surface tension can be obtained within a very short plasma treatment.

Here Reflectance and K/S value of untreated (dyed) and plasma treated Angora fibres followed dyeing is given:Sample specification % R K/S

Summary

Plasma processing has several advantages over traditional wet processing or plasma treatment is carried out for improving several properties as follows:

Soil-resistant, flame-retardant, dye and permanent press treatments can all be accomplished without creating toxic effluents.

Plasma treatment modifies the fibre surface rather than its interior, which allows the fabric to retain strength over time.

This process is applicable for all types of fibres making the modifications simpler even for inert materials. Also some special textile properties can only be obtained via plasma processing.

Consumption of chemicals is very low and this being dry process, less energy and time are required.

Thus, despite this being costly process initially (in terms of set-up), we get greater production rate, less production cost, better products and most importantly, we get finishes on fabrics that are either difficult to obtain by other processes or not obtained at all. And all these, apart from the freedom from environmental problems that current processes pose.