Chemical dyes are mainly used in industry and are commonly known as colored organic compounds that are applied to color a substrate like leather, paper, cloth, or plastic. Typically, dyes are applied to an aqueous solution and absorb different light wavelengths to change the color of other materials. So dyeing chemicals simply refers to a substance manufactured from chemicals or plants. And it's mixed with liquid and used to alter the color of a material.

Sources of Different Types of Chemical Dyes:

Chemical Dyes are classified mainly based on various parameters, of which we will look at four main and most common sources:

Sources Based:

• Organic Dyes or Natural Dyes 

• Synthetic Dyes

Ionic Nature Based:

• Anionic Dyes: Acid dye, Reactive Dye, and More.

• Non-ionic Dyes: Disperse Dye.

• Cationic Dyes: Basic Dye.

• Chromophoric Groups Based:

• Nitroso and Nitro Dyes

• Anthraquinone Dyes

• Triarylmethane Dyes

• Azo dyes

• Indigo Dyes

  
  

  Chemical Structure Based:

    1. Ready-made Dyes:

1. Water-soluble dyes: Reactive dye, direct dye, Acid dye, etc.

2. Water-insoluble dyes: Vat dye, Sulphur dye, etc.

     2. Ingrain Dyes:

1. Mineral colors

2. Azoic colors

3. Oxidation colors

Different Types of Chemical Dyes, Their Properties, Mechanism, and Application:

In this segment, you'll know about the different types of chemical dyes, their properties, and their primary mechanism. So, let's begin:

Direct Dyes:

You can clearly use these dyes straightforwardly on the fiber because they have a powerful affinity as they are known as direct dyes. Traditionally, these dyes are known as sodium salts of carboxylic acids or sulfonic acids, and "Azo" is their ultimate chromophoric group. On a quick note, they are also familiar as substantive dyes.

Direct Dyes Properties:

• These are water-soluble & anionic.

• Needed electrolytes and alkaline circumstances for the dyeing process.

• Commonly, cellulosic fiber is dyed, however, you can also apply protein fiber.

• Its fastness properties are average ratio, mostly, wet fastness is inferior. After-treatment is demanded uplifted fastness.

• They fasten to fibers with feeble hydrogen bonds and "van der Waals" forces of attraction.

• Truly, low-grade when analogized to other dyes.

• Primary Mechanism (Direct Dyes):

This dyeing basically involves three main stages, for instance, they are adsorption, diffusion, and migration. The surface of cellulosic fibers becomes anionic upon contact with water. And you need to neutralize the surface to terminate the repulsive electrolyte.

• Application:

Cotton and Viscose.

Reactive Dyes:

A halogen-containing reactive element is exist in the formation of reactive dyes and immediately becomes an inherent portion of the fiber formation by making a covalent bond. On a quick note, this type of dye is commonly applied for dyeing cotton fabrics.

• Reactive Dyes Properties:

• Common as water-soluble & anionic.

• Shows better wash, light fastness, & mild rubbing fastness

• Attach with the fiber through a covalent bond

• These are well-known in liquid, powder, and paste shape

• Needs to apply electrolytes and alkaline conditions

• Primary Mechanism (Reactive Dyes):

This dyeing mechanism is decorated with three steps.

• Exhaustion: Through electrolytes assist.

• Fixation: Through alkali assist.

• Washing-off: By the aid of a soaping agent.

• Application: 

Specifically Cotton

Acid Dyes:

Since these substances are called and familiar as acid dyes, this substance requires an acidic bath. These dyes are potentially applied for dyeing protein fibers and technically knows as carboxylic or sulphuric acid salts.

•  Acid Dyes Properties:

• Exceptionally water-soluble and anionic.

• Polyamide and protein fibers have their components.

• Exhibit inadequate wash fastness, but light fastness is flawless and pristine.

• The dye anion is the active colorant.

• Their application needs an acidic medium.

• Primary Mechanism (Acid Dyes):

• Wool might be described as, H2N—W—COOH.

• Under certain circumstances (In water), H2N—W—COOH ⇒ H3N(+)—W—COO(–)

• When acid is included, 

HCl ⇒ H+ + Cl–

H3N+—W—COO– +H+ + Cl– ⇒ Cl–+H3N—W—COOH

• Following reaction occurs after the dye is added to the wool, H3N+−Cl—W—COOH + R– SO3−+Na    ⇒   R– SO3−+H3N—W—COOH + NaCl

• Wool in Acidic Medium + Acid Dye ⇒ Dyed Wool + Salt

• Application: 

Particularly nylon (silk and wool).

Basic Dyes:

Basic dyes are commonly known as salts of organic bases and the cationic portion of the dye formation is liable for color production.

• Basic Dyes Properties:

• Completely cationic dyes. 

• Soluble in alcohol yet not happily liquefiable with water.

• Display superb shades but feeble leveling properties.

• Ordinarily, suitable for jute and acrylic.

• Shows moderate to satisfactory fastness properties.

• Primary Mechanism (Basic Dyes):

A retarding agent is required because the primary absorption of the dye is very soaring. Must maintain strictly the temperature and pH to avert unlevel dyeing. Commonly, dyeing is steered at 98°C, and to avert the structure of creases, slow cooling is essential.

• Application: 

Jute and acrylic.

Sulfur Dyes:

Suppose you're thinking to produce brown and black shades in cotton, in this case, Sulfur dyes are the best and ultimate solution. These dyes have disulfide cohesion in their formation, yet similar to vat dyes.

• Sulfur Dyes Properties:

• These dyes are water-insoluble and will need reducing agents to make them soluble.

• Used in alkaline conditions and for color fabrication oxidation is demanded.

• Electrolytes can sweeten fatigue.

• Shows moderate fastness properties.

• Mainly are cheap

• Primary Mechanism (Sulfur Dyes):

Must pursue the following route 

• Dissolving the dyestuff

• Reducing the dyes to Form a Leuco compound

• Dyeing with the Reduce dyes

• Washing off the unexhausted dyestuff

• Oxidation back to the Parent dye

• After treatment

• Dye fixing treatment

• Application:

Cotton and Viscose.

Vat Dyes:

Traditionally, they are composed of a keto group with their formation and are made water-soluble through vatting. On an important note, these dyes are alike to sulfur dyes and are usually applied for dyeing jeans or denim.

• Vat Dyes Properties:

• Organic coloring substances but not soluble in water.

• Vatting is mandated to recast water-soluble shapes, and vatting needs alkaline conditions.

• These dyes generate comprehensive span colors and brilliant shades.

• Shows amazing fastness properties without rubbing fastness.

• Can locate in powder and paste format.

• Primary Mechanism (Vat Dyes):

They contain four main steps:

• Vatting: These insoluble dyes are transformed into soluble leuco forms through reduction.

• Diffusion: These soluble leuco dyes reach within the cellulosic fiber.

• Oxidation: These soluble dyes are transformed into insoluble forms similarly.

• Washing-off: The unsettled dyes are terminated from the surface.

• Application:

Cotton.

Disperse Dyes:

Technically known as sparingly water-soluble dyes, that mainly used to dye hydrophobic thermoplastic fibers. On a serious note, these are primarily anthraquinone, substituted azo, or diphenylamine compounds.

• Disperse Dyes Properties:

• Sparingly water-soluble, non-ionic, and have low molecular weight.

• To form dispersed water needs dispersing agent.

• Exalted except for rotting and exhibiting gas fumes fade.

• These are located in powder and liquid designs.

• They have no affinity for any fiber.

• Primary Mechanism (Disperse Dyes):

Will need to follow these actions

• Dispersion or dissolution of dye molecules in water

• Adsorption

• Spreading dye molecules into the fiber inside.

• Application:

Polyester, Nylon, Acrylic, Acetate.

Azoic Dyes:

They are classically considered as mono or bis azo water-insoluble colorants and instruct coupling agents to form the color. And the most exhilarating part is these are not ready-made colors similar to other dyes.

• Azoic Dyes Properties:

• The insoluble azo group exists in their formation and is not water-soluble.

• Two baths need (developing and impregnation baths).

• These pigments are great for creating severe and bright orange, red and crimson shades.

• Shows superior washing and light fastness.

• Diazonium and coupling compounds verify their true color.

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• Primary Mechanism (Azoic Dyes):

They require two main components.

• Naphthol / Coupling component

• Diazonium salt

• Application:

Polyester, Nylon, Cotton.

Mordant Dyes:

They have no effect on textile material. And mordants are chemical binding agents that aid in their binding to fibers. These dyes are also familiar as chrome dyes since these are specifically inorganic chromium.

• Mordant Dyes Properties:

• No affinity towards textile material.

• Able to generate dark shades.

• Displays well-crafted fastness properties including leveling properties.

• Dye fiber adhesive is powerful ionic bonds.

• A metal ion exists in their formation.

• Primary Mechanism (Mordant Dyes):

Might be followed by following three processes:

• Pre-mordanting is familiar as Chrome

• Meta mordanting is cognizant as Metachrome

• Post-mordanting is well known as Afterchrome

• Application:

Natural Protein and Modacrylic fibers.

Overall, these chemical dyes need to be fast or chemically sturdy, which will not terminate by soap and water, as well as will not fade when exposed to sunlight.

FAQ:

Q - 01: Brief Definitaion of Chemical Dye?

ANS:  Generally speaking, it's a substance tooled from chemicals or plants, mixed with liquid and applied for changing the color of any material.

Q - 02: For high-quality wash fastness which classes of colorants to choose?

ANS: Indeed, it varies by counting on elements, such as vat and reactive dyes have outstanding wash fasteners on cellulosic fibers, cotton, and tetron.

Q - 03: What is an ample worthy type of dye for dyeing cotton?

ANS: I suggest choosing fiber-reactive dyes for their extensive range of shades, which contain fantastic wash fastness and come at a very reasonable price.

Q - 04: What do you think of ample worthy kinds of dyes for dyeing polyester?

ANS: Dispersed dyes always should be your leading option and best solution. Though they might demand a more heightened dyeing temperature, you must read the above article to know more.