Abstract

Textiles have undergone chemical wet processing since time immemorial. Human ingenuity and imagination, craftsmanship and resourcefulness are evident in textile products through out the ages; we are to this day awed by beauty and sophistication of textiles sometimes found in archeological excavations.

Application of ultrasonic waves, microwave dyeing, Plasma technology, supercritical carbon dioxide, and electrochemical dyeing of textiles are some of the revolutionary ways to advance the textile wet processing. . The amount of energy spent to dry the fabric and unspent dyestuffs remaining in liquor are also huge adding to the woes of processors, making processing the weakest link among the entire textile chain. To eliminate the disadvantages, super critical fluids, CO2 is the most versatile and prominently used.

This paper gives a brief idea of working principle of it and its uses for the different classes of dyes and fabrics.

Keywords: ecofriendly, economy, dyeing, energy saving.

Introduction:

Textile wet processing consumes a large amount of energy. These processes involve the use of chemicals for assisting, accelerating or retarding their rates and must be carried out at elevated temperature to transfer mass from processing liquid medium across to the surface of textile substrate in reasonable time. The present day scenario in the textile processing calls for the conservation of energy or usage of low amount of energy. This may be achieved by the various methods such as the use of radiofrequency, Electrochemical dyeing, microwaves, infrared heating etc.

Various approaches like solvent dyeing with different dyes on the several textile substrates have been experimented. None of these methods are commercially viable due to the inherent limitations. The use of ultrasonic waves and EM radiations is also one of the sources of getting energy which can be utilized in textile wet processing. Usage of water as solvent for chemicals is mostly because of its abundant availability and low cost. Problems associated with usage of water are effluent generation and additional step is needed to dry the fabrics after each step. The amount of energy spent to remove the water is also huge adding to the woes of processors, making processing the weakest link among the entire textile chain. The unspent dyestuffs remain in liquor, thus polluting the effluent. It leads to additional pollution of waste water. To eliminate the disadvantages it is proposed that certain gases can replace water as solvating medium. High pressure and temperature are needed to dissolve the dyes. Of all the gases being possible of converted into super critical fluids, CO2 is the most versatile and prominently used.

1. Ultrasonic assisted dyeing¹⁴?

1.1.  What are Ultrasonic radiations?

There is a compression or rarefaction during each cycle of wave. When ultrasonic waves are absorbed in liquid system, the phenomenon of cavitation takes place, which is the alternate wave formation, oscillation and collapse of tiny bubbles or cavities. During the rarefaction of the portion of the wave cycle, dissolved gas molecules act as nuclei for the formation of cavities, which may expand relatively slowly up to a diameter as much as 0.1 cm. and then quickly collapse during the compression portion of the cycle.

1.1.1. Source of ultrasonic:

• Mechanical transducer
• Piezoelectric transducer
• Magnetic transducer
• Cavitization