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 applied at basic or neutral condition. This dye workers is poor fastness to clean however cheaper.

These area unit the dyes which might be applied on to the materials from associate solution. These area unit most helpful for materials which might type H bonds with the coloring of materials. The direct dyes principally the fundamental dyes and were wide hailed as a result of they created it spare to use a mordant or binder in coloring cotton. the colors don’t seem to be as good as those within the basic dyes however they need higher fastness to lightweight and laundry, and such fastness is measurably improved by once treatments (diazotized and developed.) Direct dyes is used 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 offered a massive vary of recent colours, and that they imparted higher properties to the artificial materials dyes area unit currently classified in keeping with however they’re utilized 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.

This cluster was the primary of the artificial dyes to be taken out of coal-tar derivatives. As textile dyes, they need been for the most part replaced by later developments. they’re still utilized in discharge printing, and for getting ready animal skin, paper, wood, and straw. additional recently they need been with success used with some readymade fibers, particularly the acrylics. Basic dyes were originally accustomed color wool, silk, linen, hemp, etc., while not the utilization of a mordant, or exploitation agent. With a mordant like tannin they were used on cotton and material. Basic dyes offer good colours with exceptional fastness to acrylic fibers. they will be used 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 applied 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: they’re the oldest natural dyes. they need no affinity to textiles however qwacan be applied to polyose or macromolecule fibers once they are mordented antecedently with bimetallic salt. These dye aw ar capable of mixing with metalic oxides to create insoluble color on the fiber.

Sulphur dyes: These sorts of dyes and their properties ar complicated organic compounds containing sulphur. they’re insoluble in water however soluble beneath reduced condition. they’re typically applied at cotton for cheaper shades, have high wet fastness however poor lightweight 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 colored 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, referred to as Naphthols within the trade, are literally factory-made within the cloth by applying one half the dye. the opposite [*fr1] is then placed on and that they mix to create the finished color. Unless they’re fastidiously applied 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 ar in no time color on cotton & insoluble in water. they’re reduced 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). The term vat comes from the previous indigo methodology colouring in a very vat: indigo had to be reduced to lightweight kind. Vat dyes ar made up of indigo, anthraquinone and carbazole. they’re with success used on cotton, linen, rayon, wool, silk, and generally nylon. Vat dyes also are employed in the continual piece of colouring method generally referred to as the pigment application method. The dyeings made during this means have high wash and lightweight fastness.

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