Improved Textile Fiber Dyeing with Ultrasonics

Ultrasonically assisted dyeing of fibers and fabrics improves the penetration of the dye into the fiber pores and increases colour strength and colour fastness significantly. Ultrasonic dyeing is a rapid process, which can be run under mild conditions and low temperatures. The fiber structure of materials such as fabrics and textiles is not damaged by sonication and remains intact. Ultrasonication intensifies the dyeing treatment achieving better color results and a fast process.

Advantages of Ultrasonic Dyeing

  • Improved dye penetration into fibers
  • Increased colour strength
  • Improved colour characteristics
  • Rapid dyeing process
  • Improved dye uptake and color strength
  • Higher wash, rubbing, and perspiration fastness
  • Compatible with various fabrics (e.g. wool, silk, polyamide etc.)
  • Lower overall processing costs
  • Mild, environmental-friendly, green process
  • Simple and safe operation
Infographic Ultrasonic Dyeing of Wool with ultrasonic processor UP200St

Ultrasonic dyeing of wool: Sonication improves the color strength and dye penetration into the fibres significantly.

Ultrasonic homogenisers are used as reliable and efficient tools to prepare inclusion complexes (e.g. for resveratrol)

Ultrasonic homogenizer UP200St

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Ultrasonic Dyeing for Higher Colour Strength, Fastness and Quality

Ultrasonic Effects during Dyeing

Wetting & Mass Transfer: Ultrasonic cavitation and micro-streaming improves the penetration of the dye into the fiber and yarn pores of the material. Ultrasonic cavitation accelerates the rate of dye diffusion inside the fibre by perforating the external layer of the fibre, so that the dye can enter the fiber pores. Simultaneously, sonication speeds up the chemical reaction between dye and fibre.
Dispersion: Sonication breaks up droplets, agglomerates and aggregates preparing a uniform dispersion in the dye.
Degassing: Ultrasound waves release dissolved or entrapped gas molecules from the fibre into liquid so that the gas can cavitation, thus facilitating dye-fibre contact and penetration for a fast and complete fiber coloration.
Tissera et al. (2016) demonstrated that sonication is able to achieve good color strength on cotton fabric at very low temperature such as 30ºC, which was approximately 230% more than the color strength achieved in normal heating method of dyeing. Mild sonication of 0.7 W/cm2 with the UP400St under mild temperature conditions at approx. 30ºC gave significantly improved results for colour strength and a deep penetration of the dye into the cotton fabric.
A particle size analysis of the dye revealed that ultrasonication deagglomerates and disperses the hydrolyzed dye molecules during dyeing and helps the dye to penetrate deeper into the fabric. At the same time, the fiber surface and fiber morphology remains unchanged and fully intact after sonication.

Ultrasonic dyeing accelerates and improves the penetration of coloring agents in fibers and fabrics.

Effect of ultrasonic power level on the color yield
(Graph and study by Haddar et al. 2015)

Ultrasonic Dyeing for Various Fiber and Fabric Types

Ultrasonication is a efficacious, yet mild technique to dye fibers and fabrics with colorants such as organic and inorganic dyes.
Research and pilot studies have tested the ultrasonic dyeing technique successfully for various fiber and fabric types.
Ultrasonication improved the dyeing process of

  • wool
  • silk
  • angora
  • (organic) cotton & knitted cotton fabrics
  • synthetic fabrics, e.g nylon, polyester, polyamide
  • natural fibers, e.g. hemp, bamboo
  • cellulosic fabrics

SEM analysis shows that ultrasonically-assisted dyeing does not affect surface structure of (nano-)fibers.

High-Performance Ultrasonicators for Dyeing Fibers and Fabrics

Hielscher Ultrasonics is your long-time experienced partner when it comes to high-performance ultrasonic processing. We offer the full portfolio from laboratory and bench-top ultrasonicators for research, feasibility testing and process optimization to fully-industrial ultrasonic processors for large volume processing. For the ultrasonic dyeing of textiles and fabrics Hielscher offers various solutions depending on the fiber or textile and the dye.

Ultrasonic inline dyeing system for improved colour strength and fastness in a shorter dyeing time

Ultrasonic dyeing system with 2kW ultrasonicator

Hielscher Ultrasonics’ industrial ultrasonic processors can deliver very mild to very high amplitudes. Built for heavy-duty applications, amplitudes of up to 200µm can be easily continuously run in 24/7 operation. For even higher amplitudes, customized ultrasonic sonotrodes are available. The robustness of Hielscher’s ultrasonic equipment allows for 24/7 operation under heavy load and in demanding environments.
Our customers are satisfied by the outstanding robustness and reliability of Hielscher Ultrasonic’s systems. The installation in fields of heavy-duty application, demanding environments and 24/7 operation ensure efficient and economical processing. Ultrasonic process intensification reduces processing time and achieves better results, i.e. higher quality, higher yields, innovative products.

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Facts Worth Knowing

Fabric Dyes

Fabric dyes (also textile dyes) are liquid substances used to color textile materials such as fibers, yarns, and fabrics with the goal of achieving color with desired color fastness. The dyes penetrate into the fabric and change it chemically, which results in a permanent coloring.
Commonly, acrylic fibers are dyed with basic dyes, while nylon and protein fibers such as wool and silk are processed with acid dyes, and for polyester yarn disperse dyes are used. Cotton can be dyed with various types of dyes, including vat dyes, and modern synthetic reactive and direct dyes.
Reactive dyes are the most important dye type for cellulose fibres such as cotton and viscose, but they are also increasingly gaining importance for wool and polyamide. Due to the broad range of reactive dye types, they can be used for manifold dyeing techniques. Reactive dyes can be distinguished into two major types: hot (monochlorotriazine dyes) and cold reactive dyes (dichlorotriazine dyes). Using cold reactive dyes allows to run dyeing processes at room temperature because cold-type dyes are more reactive due to the presence of two chlorine atoms.
Reactive dyes are known for poor dye fixation. The problem of dye fixation occurs especially in batch dyeing of cellulose fibres, where a significant amount of salt is normally added to improve dye exhaustion (and therefore also dye fixation).

Dyeing of Cellulose Fiber

In dyeing cellulose fibres with reactive dyes the following chemicals and auxiliaries are used:

  • Alkali (sodium carbonate, bicarbonate and caustic soda)
  • Salt (mainly sodium chloride and sulphate)
  • Urea may be added to the padding liquor in continuous processes
  • Sodium silicate may be added in the cold pad-batch method.

Below is a list of dyes with Colour Index International generic names and numbers.

Common Names Synonyms C.I. Generic Name C.I.number
Alcian Blue 8GX Alcian Blue Ingrain Blue 74240
Alcian yellow GXS Sudan orange Ingrain yellow 1 12840
Alizarin Mordant red 11 58000
Alizarin Red S Mordant red 3 58005
Alizarin yellow GG Mordant yellow 1 14025
Alizarin yellow R Mordant orange 1 14030
Azophloxin Azogeranin B Acid red 1 18050
Bismarck brown R Vesuvine brown Basic brown 4 21010
Bismarck brown Y Vesuvine Phenylene brown Basic brown 1 21000
Brilliant cresyl blue Cresyl blue BBS Basic dye 51010
Chrysoidine R Basic orange 1 11320
Chrysoidine Y Basic orange 2 11270
Congo red Direct red 28 22120
Crystal violet Basic violet 3 42555
Ethyl Green 42590
Fuchsin acid Acid violet 19 42685
Gentian violet Basic violet 1 42535
Janus green Basic dye 11050
Lissamine fast yellow Yellow 2G Acid yellow 17 18965
Malachite green
Martius yellow Acid yellow 24 10315
Meldola blue Phenylene blue Basic blue 6 51175
Metanil yellow Acid yellow 36 13065
Methyl orange Acid orange 52 13025
Methyl red Acid red 2 13020
Naphthalene black 12B Amido black 10B Acid black 1 20470
Naphthol green B Acid green 1 10020
Naphthol yellow S Acid yellow 1 10316
Orange G Acid orange 10 16230
Purpurin Verantin
Rose bengal Acid red 94 45440
Sudan II Solvent orange 7 12140
Titan yellow Direct yellow 9 19540
Tropaeolin O Sulpho orange Acid orange 6 14270
Tropaeolin OO Acid orange 5 13080
Tropaeolin OOO Orange II Acid orange 7 15510
Victoria blue 4R Basic blue 8 42563
Victoria blue B Basic blue 26 44045
Victoria blue R Basic blue 11 44040
Xylene cyanol FF Acid blue 147 42135

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