Reactive dye – Why so called?
- Reactive dyes comprise a chromophore and a reactive group. ...
- They chemically react with the textile fibers by forming covalent bond. ...
- The formation of covalent bond is a chemical process which is stronger than other bonds like Van der waals forces, hydrophobic bond, hydrogen bond or coulombic attraction of ions.
Why are re-reactive dyes so called?
Reactive dyes are so called because this is the only type of dye, which has reactive group, and that reactive group reacts chemically with fibre polymer molecules and form covalent bond.
What are reactive dyes used for?
These are usually used to dye cellulosic fibers such as cotton, rayon, or flax, but polyamide, wool, silk, and acetate fibers can also be dyed using reactive dyes. Reactive dyes are so-called because this is the only type of dye that has a reactive group.
What are the common problems of Reactive dyeing?
The most common problem of reactive dyeing is dye hydrolysis. In alkaline conditions, hydroxide ion also reacts with the reactive group of the dye like the fiber, and hydrolyzed dye is generated. The hydrolyzed dye can not react with fiber, and the efficiency of the fixation is decreased.
What is reactive dye hydrolysis?
Reactive dyes are activated when used to color cellulose in an alkaline solution. However, if the dye’s concentration is kept for a long period of time, it will eventually lose its potency. The dye then reacts with the hydroxyl group of water. This process in which a dye interacts with water is known as reactive dye hydrolysis.
What do you mean by reactive dye?
Reactive dye is the dye that can react with a fibre to form a covalent link, that is forming a permanent attachment in the fibre and could not be removed by repeated treatment with boiling water under neutral conditions. Consequently, the dyes become parts of the fibre, leading to outstanding colour fastness to wash.
Why direct dyes are so called?
Direct Dyes: Direct dyes are also called substantive dyes because of their excellent substantivity for cellulosic textile materials like cotton and viscose rayon. This class of dyes derives its name from its property of having direct affinity for cellulosic fibres, when applied from an aqueous solution.
Why are reactive dyes popular?
Reactive dyes are so popular due to the following reasons: ü Good washing fastness (Rating 4 – 5). ü Very good light fastness (Rating 6). ü Lower cost.
Why reactive dyes are so called reactive dye is more suitable for dyeing of cotton fabric justify the statement?
Textile materials dyed with reactive dyes have very good wash fastness with rating about 4-5 due to strong covalent bonds formed between fibre polymer and reactive group of dye. Reactive dye gives brighter shades and has moderate rubbing fastness. Dyeing method of reactive dyes is easy.
What is the difference between direct dye and reactive dye?
Reactive dyes are usually used when dyeing dark colors. Any color that washes out is "residual" dye that was not absorbed by the yarn; it is not "bleeding." Direct Dye is a dye used in a process in which dye molecules are attracted by physical forces at the molecular level to the yarn.
What are the properties of reactive dyes?
Reactive Dyes PropertiesReactive dyes come in all shades.Powder, print-paste, and liquid are the different forms.Good Water solubility.Resistant to degradation caused by Ultra Violet rays.Good light and wash fastness.
What is the difference between reactive dye and pigment dye?
The reactive dye particles form a covalent bond with the fabric and essentially stain it the desired color. Once the bond is formed, you have one single molecule. Pigment dyes on the other hand, are insoluble molecules that sit on top of the fiber. No chemical reaction takes place.
Why reactive dyes are water soluble?
Small molecularstructures in reactive dyes provide advantages such as high solubility in water,easy removal of hydrolyzed dye, easy cleanup, rapid diffusion in the fiber at lowtemperature, and bright colors.
Who invented reactive dye?
On the occasion of 100 years celebration of synthetic dye manufacturing, two chemists of ICI Company (UK) named Stephen and Rattee tried to manufacture new dye stuff. Thus they succeed to invent a new dye in 1956 which was named REACTIVE DYE.
Why reactive dye is suitable for cotton?
Nowadays reactive dyes are widely used in dyeing cotton materials. It reacts with fiber in presence of alkali and adheres as a part of fiber. Here the dye contains a reactive group and this reactive group makes covalent bond with the fiber polymer and act as an integral part of fiber.
Why is reactive dye anionic?
Reactive dyes are anionic in character and cotton fibers also adopt anionic surface charge in water causing limited exhaustion of dye due to charge repulsion. Large quantities of electrolyte (30-100 g/l) are thus added to overcome this problem.
How many types of reactive dyes are there?
Depending on the type of reaction, the reactive dyes are broadly divided in to two categories: Dyes reacting through Nucleophilic substitution reactions. Dyes reacting through Nucleophilic addition reactions.
What is meant by direct dyes?
direct dye, also called Substantive Dye, any of a class of coloured, water-soluble compounds that have an affinity for fibre and are taken up directly, such as the benzidine derivatives. Direct dyes are usually cheap and easily applied, and they can yield bright colours.
What is the difference between oxidative dyes and direct dyes?
The main difference between permanent/demi-permanent hair dyes, and temporary/semi-permanent dyes is the type of dye they contain. Permanent and demi-permanent hair dyes use oxidative dyes, which form in the hair when the dye is applied.
What are direct dyes used for?
Direct dyes are used on cellulosic fibers when good lightfastness is needed, but washfastness is not critical. This includes window coverings, upholstery, and heavy bedding where the finished item is seldom washed or is labeled as dryclean only.
What is direct dyes in textile?
Direct dye: A class of dye that can be applied directly to cotton or other cellulosic fabrics such as rayon, silk, and wool. Direct dyes are applied in a neutral or alkaline bath of hot water. They do not require mordant or fixatives for fastness; instead, they attach with hydrogen bonds and van der Waals forces.
Why is reactive dye called reactive dye?
Why reactive dye is so called? Reactive dyes are so called because this is the only type of dye, which has reactive group, and that reactive group reacts chemically with fibre polymer molecules and form covalent bond.
What is reactive dye?
A dye, which is capable of reacting chemically with a substrate to form a covalent dye substrate linkage, is known as reactive dyes. The reactive dyes constitute the most commonly used class of dyes for dyeing cellulosic textiles, because of their good all-round properties, such as water solubility, ease of application, ...
What is the reaction of dye with terminal OH or NH 2?
Fixation of dye means the reaction of reactive group of dye with terminal –OH or-NH 2 group of fibre and thus forming strong covalent bond with the fibre and thus forming strong covalent bond with the fibre. This is an important phase, which is controlled by maintaining proper pH by adding alkali.
What are the factors that affect dye selection?
Factors considered for selection of dyes: Dye selection depends upon the following factors: 1. Selection of dying method: Dye selection depends on dyeing method, which may be: Batch wise/ discontinuous method.
What happens to the reactive group of dye during dyeing?
During dyeing the reactive group of this dye forms covalent bond with fibre polymer and becomes an integral parts of the fibre.
How to dye fabric with alkali?
At first fabric, required water and required anti creasing agent is added in the dye bath. Then sequestering agent and gluber salt of required amount is added in the dye bath. Then the bath is kept rest for 5 minutes. After that reactive dye of required amount is added in the dye bath. After adding dye in the dye bath, the bath is kept for 30 minutes. During this period exhaustion of dye occurs in the fabric. Then required amount of alkali is added for fixation of dye into the fabric. After adding alkali we will wait for 50 minutes and then we will check the shade. If shade is all right then fabric will be taken for after treatment.
What are the properties of reactive dyes?
Properties or Characteristics of reactive dye: Reactive dyes are cationic dyes, which are used for dyeing cellulose, protein and polyamide fibres. Reactive dyes are found in power, liquid and print paste form.
Why are reactive dyes so called?
Reactive dyes are so-called because this is the only type of dye that has a reactive group. This group reacts chemically with the fiber polymer molecules to form covalent bonds. This covalent bond is formed between the reactive group and terminal –OH group of cellulosic fibers and terminal –NH 2 group of polyamide and wool fiber.
What is reactive dye?
Reactive dye is a class of dye that makes a covalent bond with the fiber and becomes an integral part of the fiber. These are usually used to dye cellulosic fibers such as cotton, rayon, or flax, but polyamide, wool, silk, and acetate fibers can also be dyed using reactive dyes. Reactive dyes are so-called because this is the only type ...
What is the fixation of dye?
Fixation of dye means the reaction of reactive group of dye with terminal –OH or –NH 2 group of fibre and thus forming strong covalent bond with the fibre . This is an important phase, which is controlled by maintaining proper pH by adding alkali.The alkali used for creates proper pH in dye bath and work as the dye-fixing agent. ...
Why can't dye be stripped?
The reactive dye cannot be satisfactorily stripped from fibre due to the covalent bond between dye molecule and fibre. Stripping becomes necessary when uneven dyeing occurs.
Why is stripping reactive dye necessary?
Stripping of Reactive Dyes. The reactive dye cannot be satisfactorily stripped from fibre due to the covalent bond between dye molecule and fibre. Stripping becomes necessary when uneven dyeing occurs .
Why are dyes good for textiles?
Textile materials dyed with reactive dyes have very good wash fastness with a rating of 4-5 due to strong covalent bonds formed between fibre polymer and reactive group of dye.
What temperature do you dye a dye?
These types of dyes contain reactive groups of high reactivity. So dyeing can be done in lower temperature i.e. 32-60°C. For example: PROCION M, LIVAFIX E
What is Reactive Dyes?
Reactive dyes form a covalent bond after they contact a fabric molecule for a firm fabric bonding. Reactive dyes are very commonly used in the textile industry on different materials such as wool, silk, and cotton. Different popular applications of reactive dyes include exhaust dyeing, discharge printing, and inkjet printing.
Types Of Reactive Dyes
Many types of reactive dyes are used based on their properties in different applications. Let us know about them in detail.
Conclusion
Reactive dyeing is an essential method of coloring cellulosic fabric. They are very popular as they are used to dye almost every fabric.
What is reactive dye?
Reactive dyes are so much popular for dyeing cellulosic fabrics. They can create a wide range of shades with excellent brilliancy. For a level dyeing the materials should be prepared very well.
What is the Dyeing Method of Reactive Dye?
Firstly, we will discuss about the dyeing method of reactive dye. The following stages that are discussed here are based on the exhaust or batch-wise dyeing process. This is the basic three steps of reactive dyeing method. So, don’t confuse this with the other process.
What happens to dye after fixation?
The fixation process then results in additional dye absorption, to re-establish the dyeing equilibrium. Dye absorption and reaction with fiber continues until no dye is taken up.
Why does dyeing start with neutral solution?
Dyeing starts with neutral solution because of the little likelihood of dye reacting with the fiber. Depending upon the substantivity some reactive dye is absorbed by the fiber during this stage. This dye is capable of migration to promote level dyeing.
How to wash dyes?
Thorough washing of the dyeing using a boiling detergent solution (soaping) eliminates the remainder. The dyeing is then finally rinsed in warm water. For deep dyeing soaping must be repeated. Otherwise, the unfixed dyes must be complexed with cationic agent. This washing stage is very crucial to develop the final properties of reactive dyes in the dyed materials.
How many reactive dyes are there?
Broadly, there are mainly 3 reactive dye process are available for cellulosic fibers, applicable to both cold and hot brand dyes, as follows:
How to get a level and reproducible dyeing?
To get a level and reproducible dyeing, the material should be prepared uniformly. Goods need to be free from alkali and neutral or slightly acidic medium is preferable for the goods. If not removed completely, reactive dyes can react with sizes especially with starch.
