What are Reactive Dye? History of reactive dye?

A dye, which is capable of reacting chemically with a substrate to form a covalent dye substrate linkage, is known as reactive dye.

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. This covalent bond is formed between the dye molecules and the terminal –OH (hydroxyl) group of cellulose fibers on between the dye molecules and the terminal –NH2 (amino) group of poly-amide or wool fibers.

Reaction:

D-SO2-CH2-CH2-OSO3Na +OH-cell     =>      D-SO2-CH2-CH2-O-cell + NaHSO3

D-SO2-CH2-CH2-OSO3Na + NH2- wool   =>    D-SO2-CH2-CH2-NH-Wool + NaHSO3

Here, D= dye part.

WHY FABRICS WRINKLE?

Why do some fabrics wrinkle and others don't? Close examination of this question reveals a relationship between moisture absorption and wrinkling. Wool and cotton fabrics wrinkle, both fibers absorb water. Polyester and nylon fabrics are more restive to wrinkling; they absorb much less than the other two.

To understand wrinkling of cellulose fibers, consider the stress and strain forces within a smooth rod as it bent - see figure 43. The stretching stresses at the outer reaches of the bend provide lateral forces to adjacent polymer chains which can cause them to move. The inner polymer chains are under compression stresses – also

Why Fabrics Shrinkage?

Woven and knitted goods are 3-dimensional arrays of crimped yarns. Fabric forming processes take straight lengths of yarns and force them into 2-dimensional crimped lengths. The degree of crimp is a function of the yarn size and fabric construction.

When fabric is completely relaxed, the crossing yarns will move around in relation to each other until a stable configuration is reached. This stable arrangement, the point where the relaxed fabric no longer shrinks in width and length, is also related to yarn sizes and fabric construction. When stretching tensions are applied to the fabric, the crimped amplitude decreases and the fabric grows in the direction of the stress. 

Later when the tensions are relieved and the fabric allowed relaxing, the crimp amplitude returns to its stable configuration and the fabric shrinks. Many fabrics are stretched during wet processing as they are pulled from one operation to another. This

What are natural dyes? Advantages and disadvantages of natural dyes?

Definition of natural dyes?

The word ‘natural dye’ covers all the dyes derived from the natural sources like plants, animal and minerals. Natural dyes are mostly non-substantive and must be applied on textiles by the help of mordents, usually a metallic salt, having an affinity for both the coloring matter and the fiber. Transition metal ions usually have strong coordinating power and/or capable of forming week to medium attraction/interaction forces and thus can act as bridging material to create substantively of natural dyes/colorants when a textile material being impregnated with such metallic salt (i.e. mordant) is subjected to dyeing with different natural dyes, usually having some mordantable groups facilitating fixation of such dye/colourant. These metallic mordants after combining with dye in the fibre, it forms an insoluble

PARTS OF A SINGLE NEEDLE SEWING MACHINE AND THEIR FUNCTIONS:

The basic structure of sewing machine is the same whether it is hand-operated sewing, treadle sewing machine or electric sewing machine. The basic parts of a sewing are listed below and seen in Fig.1

Fig. 1 Parts of a Sewing Machine

1. Spool pin: It is fitted on top of the arm to hold the reel.

2. Thread guide: It holds the thread in position from the spool to the needle.

3. Tension disc: The two concave discs put together with the convex sides facing each other.