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Ultrasound Application in Textile Wet Processes

BULETIN TEKSTIL.COM/ Jakarta

What is Ultrasonic?

Ultrasound refers to sound waves that vibrate at frequencies greater than the human audible range (above 20,000 Hz). In the most basic terms, an ultrasound is any sound wave that vibrates 20,000 times per second. These sound waves may travel through and vibrate numerous media, including solid, liquid, and gas.

Ultrasonic waves

Ultrasonic vibration generator transducer device

This unique frequency of ultrasonic waves may be found in nature and is utilized by numerous creatures to communicate (bats, dolphins, dogs, and so on). Because of our hearing limitations, this frequency is almost completely inaudible to the human ear. Humans only became aware of the presence of this frequency in the 17th century, owing to Lazzaro Spallanzani’s discovery that bats create noises at this specific frequency. Until Langevin discovered a technique to generate artificial ultrasonic waves using a transducer and crystal quartz technology during the World War I.

Ultrasonic wave vibrations may be created and used for many purposes by applying electrical energy to the transducer device. Since then, ultrasonic waves have been used in a variety of applications, including navigation, engineering, and the biomedical area (which became the ancestor of medical ultrasound technology), as well as in the textile industry.

The researchers discovered that ultrasonic technology can be used as a supporting technology in certain textile processes to increase process efficiency, shorten processing time, and other benefits.

Unique Phenomenon of Ultrasonic Waves When Exposed to Liquid Medium

Ultrasonic waves can propagate and vibrate various mediums, such as solid, liquid and gas. The researchers found that ultrasonic waves applied to a liquid medium will produce a phenomenon known as cavitation.

The cavitation phenomenon happens when ultrasonic vibration waves are applied to a liquid medium (sonication). When a liquid medium is exposed to these waves, it experiences simultaneous expansion and compression in a very short period of time. This will form vacuum bubbles in the super-high-pressure liquid medium, which can perform a variety of interesting effects in the process of super-efficient liquid mixing, dissolving substances, sonication effects, and other effects.

Formation of cavitation bubbles when a liquid is exposed to ultrasonic vibration energy

Cavitation phenomenon of ultrasonic waves in liquid medium, see https://www.youtube.com/watch?v=qGSioE58YjA

Utilization of Ultrasonic Technology in Wet Processes in the Textile Industry

Textile wet processing refers to a group of processes for textile materials (yarn or fabric) that include preparation for finishing, coloring (dyeing and printing), and special finishing and involve the use of large amounts of water as a medium. Researchers discovered that applying ultrasonic waves to solutions/liquids used in textile wet processes could improve chemical reaction activity and process efficiency. This refers to shorter processing times, less chemical/water use, and less energy use, so researchers claim that wet processes using ultrasonic technology are more environmentally friendly and energy efficient. Currently, the joint venture between Weber Ultrasonics AG and Geratex Machinery Pvt. Ltd (https://www.weber-ultrasonics.com/en/reference-geratex/) has successfully produced textile wet process machines with industrial-scale ultrasonic technology.

Textile wet processing machine with ultrasonic technology produced by a joint venture between Weber Ultrasonics AG and Geratex Machinery Pvt. Ltd

  1. Desizing-Scouring and Bleaching Process with Ultrasonic Assistance

The sizing process toughens and reduces the absorbency of the fabric. As a result, the desizing procedure is used to remove the sizing agent material from the fabric. Researchers have demonstrated via scientific studies that the desizing procedure with ultrasonic aid may more effectively remove starch from materials. According to the findings of the study, the ultrasonic technique can save processing time, eliminate the requirement for enzyme raw materials, and allow desizing to be performed at ambient temperature (without heating the desizing solution bath). Researchers found that the use of biolase enzymes can be saved by up to 50% (from 2% to 1%) and speed up the process by up to 3x (from 3 hours to 1 hour only) in cotton fabric desizing. This is claimed to provide considerable efficiency in the process. The following is a comparison table of the results of conventional desizing and ultrasonic-based desizing.

Comparison of Conventional and Ultrasonic Based Desizing Results

Furthermore, researchers discovered that ultrasonic may be used for bleaching. The results show that the ultrasonic process can reduce the processing time (from 120 minutes to 30 minutes), reduce the amount of potassium persulfate consumption as bleach powder (from 1.5% to 0.5%), and eliminate the solution heating process (from 95°C to room temperature). This improves process efficiency significantly with CIE Whiteness results that are almost similar compared to conventional processes.

Comparison of Conventional and Ultrasonic Based Bleaching Results

  1. Dyeing Process with Ultrasonic Assistance

Researchers have also looked into the possibility of applying ultrasonic waves to the fabric dyeing process. Exposure to ultrasonic waves during the dyeing process of cotton knit textiles treated with reactive dyes at low temperatures can deagglomerate the hydrolyzed dye molecules. With an immersion temperature of just around 30°C (lower temperature) for 30 minutes (shorter immersion time), the use of ultrasonic in this process may improve the color of the dyeing products by up to 235% (compared to conventional dyeing processes).

Color fixation in dyeing cotton knit fabric with reactive dyes using ultrasonic and conventional methods

Apart from dyeing cotton, researchers have looked at the possibility of dyeing polyester fabrics with ultrasonic. Polyester fiber has a crystalline polymer structure and a higher glass transition temperature (Tg), requiring a higher dyeing temperature (in the 130oC range). As a result, dyeing polyester is done at high temperatures and pressures in special closed pressure vessels, which raises the dyeing process’s operational costs. However, researchers discovered that using ultrasonic vibrations in dye solutions allows staining temperatures to be done at lower temperatures (about 100°C) and at atmospheric pressure. This demonstrates that the ultrasonic technique may save energy by decreasing the staining temperature.

The Wide Use of Ultrasonic Technology in the Textile Industry in the Future

Although various study results have been discovered on the advantages of this process, its application in the Indonesian textile industry is still rather rare. This is due to the investment cost of ultrasonic technology equipment, which are still somewhat more expensive than conventional wet process machines, therefore the tendency to invest in ultrasonic technology remains fairly low. Furthermore, firms that may provide this technology are still very rare. Even so, ultrasonic technology in textile wet processes has excellent applicative potential by increasing the efficiency of production operations, lowering production costs, saving energy, and using chemicals more efficiently than conventional methods.

(Red B-Teks/Andrian Wijayono)

Magister Rekayasa Tekstil & Apparel, Politeknik STTT Bandung

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