Servizio Comunitario di Informazione in materia di Ricerca e Sviluppo - CORDIS

Continuous and semi-continuous treatment of textile materials integrating corona discharge

Impregnation processes are very exigent in what concerns uniformity of the materials. Any deficiency at this level creates irreparable damages in the quality of the products obtained.

All cellulosic fibres are hydrophobic in raw stage, especially because a large amount of impurities form a barrier to the aqueous bath, preventing penetration and diffusion into the fibre structure. The impregnation of this type of fabrics, during treatment processes in continuous and semi-continuous, demand a high and completely uniform capability concerning bath absorption, to get an optimal yield and homogeneous results in preparation, dyeing, printing and final finishing. Due to natural hydrophobicity, these exigencies are very difficult to accomplish. In practice the elimination of this technical problem obligates to use several wetting agents, to reduce the velocity of materials or to increase impregnation's bath temperature.

The most important consequences of these practical procedures are:

The use of wetting agents in recipes of impregnation baths means an increase of costs, increase of pollution discharges and problems with formation of foam;

The decrease of velocity implicates a decrease of production levels;

The increase of bath temperature means higher energetic costs and can contribute to the formation of aggregates of products present in the impregnation bath.

The benefits of previous uniform hidrophilisation of cellulosic materials which will be impregnated in a foulard are considered of fundamental importance and are the basic support of the introduction of CORONA plasmatic technology, able to modify the surface of the materials in controlled conditions in order to achieve a very positive behaviour during impregnation.

In CORONA treatment, an electrical discharge is produced between an electrode and a counter-electrode turned on earth, keeping a difference of potential around 10000 volts. Fabric moves continuously between the electrodes with controllable velocity and adequate tension.

Material's temperature and humidity are defined in order to optimise the discharge effect. Cotton temperature must be set under 40?C and humidity rate under 8%. Discharge is made in air at ambience pressure and temperature. The main cellulosic fibres that are submitted to CORONA discharge are cotton, flax, hemp and blends with synthetic and artificial fibres if cellulosic are present in higher percentage. A large number of other cellulosic fibres, less used in textile industry, can also be treated using this technology.

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4800-058 GUIMARAES
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