About the use of Direct dye in the Textile Industry 

Definition

Direct dye is an anionic dye with substantiality for cellulosic fibers that is typically applied from an electrolyte-containing aqueous dye solution.

Introduction

Direct dyes maintain sulphonic acid groups in their structure and are anionic dyes that dissolve in water. The fibers immediately absorb them. Direct Yellow 11 was the first synthetic direct dye to be discovered by J. Walter of Geigy in 1883. Direct dye, according to the SDC definition from 1956, is “Anionic dyes substantive to cellulose when applied from an aqueous bath containing electrolytes.”

Van der Waal and hydrogen bonding hold dyes to the fiber. Direct dye has good lightfastness, but its wash fastness loses greatly. Small and water-soluble color particles result in low wet fastness. Although after-treatments can make it better. These dyes are superior to others in terms of price, higher light resistance, simplicity of use, and faster drying times.

The direct dyeing technique is easy and affordable. additionally, in the case of direct dyeing, post-processing was necessary to enhance the color of the dyed materials. Dye has the power to color textile proteins like nylon, wool, and silk.

The electrolyte was necessary for the efficient depletion of this dye. At 80°C, maximum tiredness occurs. This is the fundamental explanation for why it gives cellulosic materials the appropriate shade

Why are direct dyes called substantive dyes?

Substantive dyes are another name for direct dyes. This dye attaches to the fiber via non-ionic forces and has a direct affinity for the fibers. The dyeing procedure costs less. In water, dyes separate into sodium cations and dye anions.

It is used to color both proteins and cellulose fibers, including wool and silk. It needs post-treatment to increase shade depth. Due to its highest substantivity towards fiber, it can be applied directly to the textile material, hence the name “direct dye.”

Because common salt or Glauber salt is used, direct dye is sometimes known as “salt colors”. It also goes by the name “substantive dye.”

Chemical Structure Of Direct Dye

Properties of direct dyes

  • It is water soluble.
  • Nature is anionic
  • Excellent light fastness
  • Wash fastness is not so good.
  • Applied primarily to cellulosic fibers but appropriate for protein fibers as well, such as nylon, silk, and wool
  • Shorter cycle of death
  • It contains carboxylic acid or the sodium salt of sulfuric acid.
  • It can be used to color protein fiber and has a great affinity for cellulose fiber.
  • Comparably affordable.
  • Simple to diffuse into fiber.

Types of Direct dyes

Based on migration test and salt control ability these dyes are classified as follows-

  • (Self-leveling) -Class  A
  •  (Self- Controllable) – Class B
  • The Class C- (Temperature Controllable)

Class – A – Dyes move easily

High leveling power they may first distribute the dye unevenly, but additional boiling will smooth things out.

Class B: Limited leveling power

Controlled salt addition is required to cause dye depletion.  It is really challenging to restore the levelness if these dyes are not absorbed evenly in the beginning.

Class C: These are not self-leveling and are extremely salt-sensitive

These dyes need further temperature control because their exhaustion cannot be satisfactorily managed by the use of salt alone.

Characteristics and Advantages:

  • One of the defining characteristics of direct dyes is their impressive range of shades and hues.
  • They encompass an extensive color spectrum, from soft pastels to rich, deep tones, providing endless possibilities for creative expression.
  • These dyes can produce both bright and subdued colors, allowing artists and designers to achieve the desired effect with precision.
  • Direct dyes are known for their excellent lightfastness, meaning they can withstand prolonged exposure to sunlight without significant fading.
  • Furthermore, direct dyes possess good wash fastness, enabling the colors to withstand multiple laundering cycles without noticeable fading or bleeding. This quality is particularly important in the textile industry, where durability and color retention are key factors

Safety and Sustainability Considerations

As with any chemical product, safety, and sustainability are important aspects to consider when using direct dyes. Manufacturers and users should ensure proper handling, storage, and disposal of these dyes to minimize environmental impact. It is crucial to follow guidelines provided by the manufacturers to ensure safe and responsible usage.
In recent years, there has been a growing demand for sustainable and eco-friendly dyeing practices. While direct dyes have traditionally contained synthetic components, efforts are being made to develop eco-friendly alternatives derived from natural sources. These advancements aim to reduce the environmental footprint associated with dye production and usage.

Conclusion

In conclusion, direct dyes continue to be a popular choice for textile artists, designers, and enthusiasts due to their vibrant colors, ease of use, and versatility. As the world of fashion, art, and design evolves, direct dyes remain a reliable tool for adding a splash of brilliance and creativity to textiles, allowing individuals to express their unique style and create visually captivating pieces

MD. Foysal Kazi
Department of Textile Engineering
BGMEA University Of Fashion & Technology (BUFT)
Campus Ambassador at Crsytalline Textile Solution

Leave a Reply

Your email address will not be published. Required fields are marked *