Mercerizing is one of part of wet processing technology. Mercerizing is the special type of treatment. Mercerizing is done for get some special properties of the textile materials. By the mercerizing process the physical properties of the material changes. After scouring and bleaching process, mercerization is done.
Mercerizing is the process of subjecting a vegetable fiber to the action of a fairly concentrated solution of a strong base (Sodium hydroxide 50-70 deg Tw and 18 degree Celsius temperature) so as to produce great swelling with resultant changes in the fiber structure, dimensions, morphology and mechanical properties.
Mechanism of Mercerizing: We know that fiber cell structure is different from one to another. Some cell structure is triangular, some are oval, some are hexagonal, and some are zigzag and many more. When light falls on that cell it reflects the light as per its cell structure. Sometime this reflection is regular, some time it is not. It affects the luster of the fabric surface. For getting a regular reflection from the fiber it pass through a process called mercerizing process.
By mercerizing process the strength of the fiber increases up to 20-30%. Cotton fiber’s shape become round when it shrink in the solution of caustic soda (NaOH). The lumen becomes small and the cell wall become greater for this reason, strength of the fiber increased. The surface of the fabric become fine and light reflects on it constantly; so the luster of the fabric increase, the swelling power of the fiber also increase. Generally low twisted yarn is suitable for mercerizing. Mercerized fabric is more suitable for dyeing and printing than the bleached fabric.
Effects of mercerizing: Different types of changes are occurred for mercerizing in the cotton fabric. Following changes are the most important:
- Shrinkage in the area of the fabric.
- Tensile strength of the fabric increases.
- Fabric luster also increases.
- Hygroscopicity of the fabric increases.
- Capability for absorbing dyes increases.
- Preferential absorption of sodium hydroxide during the treatment.
- Mercerizing increased action of lower temperature.
- Possible compound formation soda cellulose.
Luster of the fabric is the most vital point. Attraction of the fabric depends on the luster of the fabric. Luster of fabric depends on various factors. They are as follows:
- Cross-section of the fiber.
- Staple length of the fiber.
- Wall thickness of the fiber.
- Concentration of Sodium hydroxide.
- Temperature of the mercerizing solution.
- Percent stretch.
- Yarn construction.
- Yarn twist.
- Doubling of yarn.
- Degree of singeing.
- Application of tension.
- Rate of drying.
Mercerizing increases the luster and strength of the fabric. Generally mercerizing is done for cotton. Mercerizing depends on the requirement of buyer. The price of the mercerized fabric is higher than bleached fabric.