CLASSIFICATION OF DYES

The English chemist William Perkins accidentally discovered the synthetic dye, mauve, in 1856, while he was trying to synthesize quinine in aniline. Before that time, all coloring materials were extracted from barks, roots, seeds, leaves and shellfish. Most synthetic dyestuffs are made from coal-tar derivatives. Their manufacture is a highly complicated technical operation, which is constantly changing. There is variation in the manner in which different fibers respond to dyestuffs and even the same fibers do not produce a full range of colors with a particular type of dye.

Basic or Cationic Dyes

This group was the first of the synthetic dyes to be taken out of coal-tar derivatives. As textile dyes, they have been largely replaced by later developments. However, they are still used in discharge printing, and for preparing leather, paper, wood, and straw. More recently they have been successfully used with some readymade fibers, especially the acrylics. The name means that these are dyes with an organic material, which is soluble in a simple acid. Basic dyes were originally used to color wool, silk, linen, hemp, etc., without the use of a mordant, or using agent. With a mordant like tannic acid they were used on cotton and rayon. Basic dyes give brilliant colors with exceptional fastness to acrylic fibers. They can be used on basic dyeable variants of nylon and polyester.

Explanation of different types of yarn

1. Single yarn

Single yarn is the simplest continuous strand of textile mtl composed of one of the following: 

(i) Continuous filament

Filament consists of very long, thin cylinder type fibre twisted together. Continuous filament yarns are the simplest in the structure but can be subjected to many modifying process for changing their texture, extensibility, bulk and other properties. In the manufacture of man made filaments, a solution is forced through very fine holes of spinneret, at which point the solution solidifies by coagulation, evaporation or cooling.

Continuous filament yarns in fabric form usually have excellent strength & uniformity. This yarn can be made much finer in linear density and diameter than staple yarns. In an untextured form, continuous filament yarns are not posses a combination of good covering power tactile qualities, comfort and a pleasing appearance. Silk is a natural filament, synthetic filament yarn is used to produce silk like effect.

Filament yarns are two types:-

a) Monofilament: Which containing one filament. e.g. Silk.

b) Multifilament: Which contains two or more filaments e.g. Nylon.

Types of Natural Dyes

Natural dyes can be sorted into three categories: natural dyes obtained from plants (Indigo), those obtained from animals (cochineal), and those obtained from minerals (ocher). Although some fabrics such as silk and wool can be colored simply by being dipped in the dye, others such as cotton require a mordant.

A mordant is an element, which aids the chemical reaction that takes place between the dye and the fiber so that the dye is absorbed. Containers used for dying must be non-reactive (enamel, stainless steel.) brass, copper or iron pots will do their own mordanting. Not all dyes need mordants, such as lichens and walnut hulls, they are called substantive dyes. If they do need a mordant, they are called adjective dyes.