Difference between Reactive and Vat Dyes

Reactive dye and vat dye aren’t of same dye class, right? Of course, we all know about it. So, there’s some crucial difference between reactive and vat dyes. Before finding out the difference between reactive and vat dyes, let’s know the basic of these two dyes.

Let’s get started….

Reactive dye

Reactive dye is an anionic dye which is soluble in water. It has reactive group in it which reacts with the fiber and makes a covalent bond with it. Thus it becomes an integral part of the fiber. It is the youngest and most important dye-class for cellulosic materials. For cellulosic materials, worldwide consumption of reactive dyes in mid-1980s was about 10-12% whereas in Japan alone it represented about 40% of total dye consumption.

Now isn’t the question peeps through your mind that why this dye is so popular? The answer might be the properties of reactive dyes like high brilliancy at lower cost, wide range of shades, ease of application and of course its reproducibility. 

Let’s talk about its fastness properties. The light fastness of reactive dye is very good with a rating of 6. Their wash fastness is also very good as they form a strong covalent bond with the fibers. This bonds let them tightly attached with the substrate. They have moderate rubbing fastness.

Procion, Cibacron, Remazol are the most commonly used commercial reactive dyes.

Cellulose as well as protein both the fibers can be dyed with reactive dye. For fixation it requires alkaline condition. Reactive dyeing method can be explained in three steps: 

  • Exhaustion
  • Fixation
  • Washing off

In practice, you will find out reactive dyeing carried out in discontinuous or semi-continuous process in factory. But it is so simple to dye with reactive dye at home. So, if you want to know how to use reactive dye for dyeing your favorite outfit then click here.

You will find out different reactive dyes like hot brand, medium brand, cold brand. Again, alkali controllable dyes, salt controllable dyes or temperature controllable dyes, DCT, MCT, Vinylsulphone dyes. Pretty confusing right?

So, if you wanna know about detailed classification of reactive dye then click here

Vat dyes

Vat dye is a water insoluble anionic dye. For the application of vat dye, vatting process is required. In this process, vat dye is reduced by sodium hydrosulphite. After dyeing procedure, it is oxidized to convert to its mother form or you can say the original insoluble form.

So, dyeing with vat dye involve three steps:

  • Vatting, a reduction process carried out with sodium hydrosulphite and caustic soda
  • Dyeing, impregnation of substrate with the dissolved dye
  • Oxidation to convert the dye into its original pigment form.

This dyeing procedure also carried out at alkaline medium like reactive dyeing. Vat dyes have excellent all round fastness properties that can’t be achieved by the other dye class. They are ideal for colored woven goods such as handkerchiefs, shirtings, and toweling.

This dye is easily reducible. So, when it undergoes washing at boil under alkaline condition, it may show poor fastness properties. Otherwise, it has very excellent fastness properties.

Topic

Reactive dye

Vat dye

MECHANISM

Covalent Bond Formation.


Good Affinity for the Cellulosic Fibers.


Smaller Molecule Size.

Vatting Process:

 {Converting Water-Insoluble pigment into a Water-Soluble dye}.

Redox Reaction occurs

Reducing agent HYDROSE provides the attraction for the fibers. Again the dye is converted into the insoluble form inside the fiber

STRUCTURE

SOLUBILITY

Easily Soluble in Water.

Good Affinity for Water.

Polar Nature.

In-Soluble in Water.

Adding Reducing Agents to become Soluble.

 

CHARGEABILITY

Negatively Charged.

Remove Negative  Charge by Adding Salts,

i.e. NaCl

Negatively Charged.

Alkali is Used for Removing Charge.

 

SUBSTANTIVITY

Good Substantivity for the Fibers.

High Degree of Fixation Efficiency.

pH Range: 7 - 11

Substantivity is good for Cellulosic Fibers.

High Fixation because of Reducing Agents.

pH Range :  12 - 15

FASTNESS PROPERTIES

Washing    : Good   

Rubbing  : Moderate

Lightening   : Good

Chemical  :  Stable

Perspiration: Good

Washing        :  good

Lightening      :  Good

Crocking         : Poor

Chemicals       : Average

Perspiration   : Good

APPLIANCES

They are Applied to Cellulosic, Protein and Polyamide Fibers;

 i.e. Cotton, Wool.

They are Applied to Cellulosic and Protein Fibers; i.e. Viscose Rayon, Wool.

COLOUR RANGE

Wide Range of Colors.

Brighter Shades.

All Colors are Achievable.

Large Range of Colors.

Dark Shades Available.

Major Colors: Indigo, Green and Black. 

ENVIRONMENT BEHAVIOUR

Non-Environmental Friendly.

Carcinogenic Dye.

Non-Environmental Friendly.

Cancer Causing Dye

COST

U.S: 0.5 - 1.8 $/Kg.  

Cheap

U.S: 9.9 – 13.98 $/Kg

Average     

 

EASE OF PROCESS

Easy

Difficult

POPULARITY

Widely used for dyeing garments i.e. Ladies wear, Men’s wear, Kid’s wear

Widely used in dyeing jeans or denims

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