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Plasma conquering the textile industry |
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European scientists and industrialists working on the Plasmatex project wish to demonstrate the feasibility of a technology of the future: textile processing using plasmas at atmospheric pressure. Three prototypes are now in use by several partner companies in various fields to study the feasibility of a particularly innovative system and examine its results and potentials in different contexts.
When you increase the temperature of matter, it passes successively through its solid, liquid and gaseous states. But if you continue to heat it, it |
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undergoes a further transformation of a different kind. Collisions between particles of matter increase and the initial gaseous state, comprising neutral molecules or atoms, develops into an ionised state with an equal density of positive ions and negative electrons. This mix of charged particles is called plasma and it is commonly found in nature. Interest in plasmas is not new. They have been used in neon lighting, microelectronic etching, research into thermonuclear fusion and in many surface treatment processes, in particular in the metal and polymer sector. Research laboratories in the textile industry have also been experimenting with plasma processing in a range of applications. Just the surface"Unlike liquid 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 angströms," (1) explains Roshan Shishoo, Director of the Institute of Fibre and Polymer Technology Research in Mölndal (Sweden) and coordinator of the European Plasmatex project. 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 flammability. And while it is difficult to dye synthetic fabrics, the use of reactive polar functions results in improved pigment fixation. Finally, with plasma containing fluorine, which is mainly used to treat textiles for medical use, it is possible to optimise biocompatability and haemocompatability - essential for medical implants containing textiles. The challenge of the vacuumMoreover, plasma technologies are based on physical processes with much greater advantages - especially in environmental terms - than traditional chemical processes used in the textile industry, which use up a great deal of water and energy and involve high waste?processing costs. This is because "dry" processing using plasma technology has a much higher process speed (just a few minutes, or even seconds). "Despite all these 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", continues Roshan Shishoo. "All the technologies developed to date are based on the properties of low?pressure plasmas. The process must take place in an expensive, closed?parameter vacuum system and cannot be used for production lines operating at room temperature, with machines processing fabric two metres wide at high speed". Three prototypes in the service of industryThis is the challenge that a new generation of APPS (Atmospheric Pressure Plasma Processing Systems) developed by Plasma Ireland wishes to overcome. For the first time, this company has developed a technology offering a comparable performance at ambient pressure to that of "glow discharge" plasmas requiring a partial vacuum. Plasma Ireland has provided three prototypes that can be used to study the industrial feasibility of APPS technology and examine at full scale the results obtained in light of the physical properties of different types of plasma, as well as the way the plasmas interact with various materials. The first of these prototypes, installed at the IFP, has been made available to the Swedish companies Almedhals (specialising in the adhesion of polymer coatings), Borgstena Textile Sweden (automobile textiles) and SCA Hygiene Paper. The second is in Germany, at Kirchhoff, a company which works with wool fibres and is interested in using the plasma technologies as a possible way of eliminating felting. This same equipment will be made available at a later date to Polisilk of Spain, a suitcase manufacturer which wants to improve the binding properties of polypropylene?based coatings. The third prototypes is being tested by the British group Scapa, which specialises in products for the printing and textile industries. "Europe should soon have an innovative and competitive tool which we intend to make available internationally," believes Tony Herbert, project manager at Plasma Ireland. "There are only two or three other systems using plasma at atmospheric pressure currently at the development stage - in Japan and the United States - but no wide?ranging application for the textile sector is available yet. So the prospects are extremely promising". |
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 Plasma produces no more than a surface reaction and does not alter the internal composition of fabrics. The use of plasmas makes it possible to ensure biocompatability of textiles for medical use, impart hydrophilic or hydrophobic properties, reduce flammability and improve pigment fixation. |
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