Dyeing Fabric is the most common things that every Textile Engineers should have to know. There are many kind of dyes are used to dyeing fabric. Maximum of them are suitable for fabric dye and yarn dyeing.
Dye staffs used to fabric dyeing are:
Direct dyes: These dye staffs are generally sodium salt of sulphonic acid. They have direct affinity to cellulosic fibre. They are water soluble and needs salt addition in the dye bath. Should be applied at alkaline or neutral condition. Poor fastness to wash but cheaper for fabric dyeing.
Basic dyes: These are generallyu ammonium, sulphonium or a uxonium salt. Famous for bright shade during dyeing fabric. Water soluble and application on cotton and other cellulosic fibre and leathers.
Acid dyes: chemically acid dyes belongs to various subclasses such as nitro nitroso, monoazo, diazo, xanthance azine, quinoline, anthraquinone etc. they are water soluble and have affinity to wool, silk and nylon fibres to dyeing. They are applied to the fibres through neutral or acid dye bath.
Mordant dyes: they are the oldest natural dyes. They have no affinity to textiles but can be applied to cellulose or protein fibres in order to dyeing fabric when they have been mordented previously with metallic salt. These dye staffs are capable of combining with metallic oxides to form insoluble colour on the fibre .
Sulpher dyes: These are complex organic compounds containing sulphur. They are insoluble in water but sluble under reduced condition . they are usually applied cotton for cheaper shades, have high wet fastness but poor light fastness during dyeing fabric.
Azoic dyes: these are not ready made dyes. Fibres are firstly impregnated with a coupling component like bita nepthol and then combined with a diazotized base to producer insoluble dye staffs into the fibre. Their main use on cotton but also can be used to dyeing wool silk and fur.
Vat dyes: they are very fast color on cotton and insoluble in water. They are reduced by strong reducing agent to pr9oduce leuco vat and at this stage they are soluble in water. After impregnation they are again oxidized to their original insoluble form.
Reactive dyes: these dye staffs directly combinds with cellulose by chemical bonding i.e. covalent bonds are produced. They have excellent wash fastness. Mainly used on cotton dyeing . can also be applied on wool, silk and nylin dyeing. Dyeing is carried out in an alkine bath.
Disperse dyes: these dye staffs are very suitable for synthetic fibres for example polyester, nylon, acrylic, cellulosic acetate, etc. high temperature dyeing methods are suitable for these dye staffs but carrier dyeing method can also be applied.
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