Detail Study of screen printing and Dyes

Direct dyes: These dye staffs area unit usually Na salt of acid. they need direct affinity to plastic fiber. sorts of dyes and their properties area unit water soluble and desires salt addition within the dye tub, ought to be apply at basic or neutral condition. This dye workers is poor fastness to clean however cheaper.

These area unit the dyes which might be apply on to the materials from associate solution. These area unit most helpful for materials which might type H bonds with the coloring of materials.

Direct dyes

primarily replaced basic dyes and gained wide popularity because they eliminated the need for a mordant or binder when dyeing cotton. Although their colors are not as vibrant as those produced by basic dyes, direct dyes offer better fastness to light and washing. Post-treatments—such as diazotization and development—can further enhance this fastness.

Manufacturers use direct dyes on cotton, linen, rayon, wool, silk, and nylon.. These dyes sometimes have chemical group linkage –N=N- and high mass. they’re water soluble due to acid teams.

Direct orange twenty six could be a typical substantive dye.

Fig: Direct orange twenty six

Synthetic dye:
Dyes derived from organic or compound area unit called artificial dyes. samples of this category of dyes area unit Direct, Acid, Basic, Reactive dye, Mordant, Metal advanced, Vat, Sulphure, Disperse dye etc. artificial dyes quickly replaced the standard natural dyes.

They value less, they offer a massive vary of recent colours, and that they impart higher properties to the artificial materials dyes area unit currently classify in keeping with however they’re utilize in the coloring method.

Basic dyes: These sorts of dyes and their properties area unit usually ammonia sulphonium or auxonium salt, known for bright shade, water soluble & application on cotton & different plastic fiber and leathers.

Basic dyes were the first synthetic dyes develope from coal-tar derivatives. While modern developments have largely replaced them in textile dyeing, they still play a role in discharge printing and in coloring leather, paper, wood, and straw. More recently, manufacturers have successfully used basic dyes with certain man-made fibers, particularly acrylics.

Originally, dyers used basic dyes on wool, silk, linen, and hemp without a mordant. With a mordant like tannin, they could also dye cotton and other cellulosic fabrics. Basic dyes produce bright, intense colors and offer excellent fastness on acrylic fibers. They also work on basic dyeable variants of nylon and polyester.

Basic Brown one is associate example of a ion dye that’s pronto protonated beneath the pH a pair of to five conditions of coloring.

Acid dyes: with chemicals acid dyes belong to varied subclasses like nitro.nitroso, monoazo. diazo. xanthane. azine, quinoline, anthraquinone etc. These sorts of dyes and their properties ar water soluble and have affinity to wool, silk and nylon fibers. they’re apply to the fibers through neutral or dyestuff tub.

Acid dyes ar soluble anionic dyes, containing one or a lot of sulphonic acid substituents or alternative acidic teams. associate example of the category is Acid Yellow thirty six.

Fig: Acid yello36
Most artificial food colours fall during this class. The colouring method is reversible and should be delineate as follows:

Mordant Dyes:

Mordant dyes are among the oldest natural dyes. They do not have a direct affinity for textiles, but dyers can apply them to cellulose or protein fibers after treating the fabric with metallic salts (mordants). These dyes form insoluble complexes with metallic oxides, which then fix the color onto the fiber.

Sulfur Dyes:

Sulfur dyes are complex organic compounds that contain sulfur. Although insoluble in water, they become soluble under reducing conditions. Dyers primarily use sulfur dyes on cotton to produce economical dark shades. These dyes provide good wet fastness but have poor light fastness.

Azoic dyes: These aren’t readymade dyes. Fibers ar first of all fertilised with a coupling element like B-nepthol and so combined with a diazotised base to provide insoluble dye staffs into the fiber. Their main use on cotton however can also be color silk & fur.

Azo dyes contain a minimum of one radical (-N=N-) connected to 1 or usually 2 aromatic rings. These dyes ar used primarily for bright red shades in colouring and printing since most alternative categories of quick dyes ar lacking in smart red dyes. Azoic dyes, referr to as Naphthols within the trade, are literally factory-made within the cloth by applying one half the dye.

the opposite [*fr1] is then place on and that they mix to create the finished color. Unless they’re fastidiously apply and well washed, they need poor fastness to rubbing or crocking.

The production of dark-blue red early dye from the subsequent 2 parts is associate example.

Vat dyes: These sorts of dyes and their properties are in no time color on cotton & insoluble in water. they’re reduce by robust reductant to provide leuco-vat & at this stage they’re soluble in water. once impregnation they’re once more change to their original insoluble kind.

The vat dyes ar insoluble complicated polycyclic molecules supported the compound structure (ketoforms).

Vat Dyes

The term “vat” originates from the traditional indigo dyeing process, where indigo had to be reduce in a vat (container) to make it soluble for dyeing. Once applied to the fabric, the dye would oxidize and return to its insoluble form, becoming colorfast and durable.

Vat dyes are derive from compounds such as indigo, anthraquinone, and carbazole. They are widely use on cotton, linen, rayon, wool, silk, and occasionally on nylon.

These dyes are also use in continuous piece dyeing, particularly in a method known as the pigment application process, which combines the stability of vat dyes with high production efficiency.

Vat dyes are value for their exceptional fastness to light, washing, and chemicals, making them ideal for industrial and durable textile applications.

 The dyeings made during this means have high wash and lightweight fastness.

An example of a dye is Vat Blue four (Indanthrene)