Mercerizing in Textile – An Overview

Unveiling the Brilliance: The Art of Mercerizing

Sinthia Zaman
B.Sc. in Textile Engineering
Textile Engineering College, Zorargonj, Chattogram

Introduction:
Mercerization is a physico-chemical process in which textiles (typically cotton) are treated with a caustic soda (NaOH) solution to improve properties such as smoothness, fibre strength, shrinkage resistance, lustre and dye affinity. It’s a kind of treatment that turns ordinary cotton fibre into something extraordinary by swelling and rearranging its cellulose structure. This process enhances the fibres tensile strength, improves their surface properties, improves their softness, and makes them more stable and physically compact ,giving them a lustrous appearance. 20–30% dye and chemical savings while dyeing after mercerizing. It is very desirable and its influence is reflected in the production of premium textiles these days. Because of its lively colour, luxurious shine, and enhanced durability, mercerized cotton fibre is a preferred option for many textile applications.

Physico-Chemical Process:

Physical changes:

1. The kidney-shaped X-section of cotton fibre has a lumen in the middle.
2. The fibre’s cellulose starts to swell in an aquatic sodium hydroxide solution.
3. The fibre in the X-section instantly takes on an elliptical shape.
4. After more swelling, the segment ends.
5. Until the luman is gone, the fibre width increases by at least 25–30%, and the cellulose wall swells inward.
6. Following the washing process, the cellulose starts to shrink.
7. A final, further shrinkage happens after drying, and the lumen does not recover.

Chemical changes:
1. When combined with concentrated sodium hydroxide, native cellulose (Cellulose-I) produces alkali cellulose. After neutralization and washing, cellulose-II is created.

C6H7O2(OH)3 + NaOH = C6H7O2(OH)2(ONa) + H2O = C6H7O2(OH)3  +NaOH

Cellulose-1         Alkali      Alkali cellulose Cellulose-2

2. Alkali penetrates the lattice, breaking internal hydrogen bonds and increasing the amount of available OH in cellulose II by around 25%.

3. Consequently, the mercerized cotton has an increased affinity for water, dye, and other substances.

Impact of the Process of Mercerizing:
The reason for the higher strength is-

1. Increase in molecular orientation
2. The lumen is removed.
3. Length-wise shrinkage takes place, reducing the number of weak fibre linkages.

Absorbency and dye affinity rise as a result of-

1. Expand the amorphous area.
2. A change in the crystal structure
3. An increase in available OH groups contributes to dye affinity.

Increased lustre as a result of-

1. The kidney’s form being nearly round in the X-section
2. De-convolution happens or the convolution twist reduces
3. Transparency and surface roughness are improved.

Factors Affecting the Mercerizing Condition:

1. Varying temperatures have an impact on lustre. Lower temperatures result in increased lustre, dye affinity, and tension that are required to prevent shrinkage.
2. Several additional treatments destroy the fabric.
3. Mercerization without tension results in shrinkage and a lack of lustre.
4. Up to a 13% concentration of caustic enhances dye absorption and tensile strength.
5. As the mercerizing tension rises, the tenacity and elastic modulus rise noticeably.
6. The mercerizing fluid contains a wetting agent to speed up the process by allowing NaOH to penetrate quickly and effectively.
7. Before applying, the cost of the wetting agent should be considered.
8. As temperature and time increase, caustic concentration decreases.

Process of Cotton Fabric Mercerizing:

1. Fabric that has been cleaned and bleached is run under tension for two to three minutes through a padded mangle filled with a 55°–65° Tw NaOH solution.
2. A squeezing rollar is used to squeeze supported fabric.
3. After that, wash in appropriate tension with hot (70°C) and cold water.
4. To eliminate any leftover caustic, 1° Tw H₂SO₄ is applied to the washed fabric.
5. After that, the fabric is dried and cleaned in cold water.

Uses:
It is a desirable option for both manufacturers and customers due to its improved lustre, vivid colours, higher extending durability, and decreased shrinking. Mercerized cotton yarn is widely available in a range of products that prioritise comfort, look, and durability, from stylish bed linens and smooth towels to luxury tailored dress socks and fashionable apparel. Products that frequently use mercerized cotton include the following:

• ‍Bed linens
• Towels
• T-shirts
• Outfits: Designer Socks
• Tablecloths

Advantages:
Compared to untreated cotton, mercerized cotton yarn has several advantages. Some of these benefits include:

1. Increased brightness and smoothness
2. Enhanced absorption of dye
3. Higher resistance to pulling
4. Decreased shrinkage of the textiles

Environmental Impact:
Though mercerized cotton yarns have obvious advantages; we also need to take the mercerization process’s environmental effects into view. Environmental harm may result from the process’s use of chemicals like caustic soda and water resource consumption. Still, environmentally friendly methods can lessen the damage chemical mercerization does to the environment. Textile mills can reduce the environmental impact of this process by putting into practice methods including reusing mercerization effluent, treating wastewater to remove chemicals, and using membrane technology to recover caustic soda. Since the market for mercerized cotton products is growing, the textile sector needs to concentrate on ethical and sustainable methods to reduce mercerization’s financial and environmental impact.

Care:
It’s necessary to take proper care of any mercerized fabric to maintain its durability and quality. When particular care instructions may differ according to the product, mercerized cotton can generally be cared for in the following ways:

1. Depending on the label on the clothing or yarn, wash by hand or by machine.
2. Hot water and strong chemicals might cause the fabric to get worse, so it is advised to use cool water and harmless detergents.

For best results after washing, remove any extra moisture by laying the item flat or rolling it in an absorbent towel and then providing it air dry.

FAQ:

1. What is mercerized cotton?
Ans: Mercerized cotton is an outstanding substance with many different kinds of applications and benefits.

Mercerized cotton acquires improved lustre, improved dye uptake, higher tensile strength, and less shrinkage by treating cotton fibres with sodium hydroxide, applying tension reduction, and rinsing the yarn.

Although there are worries about how the mercerization process affects the environment, sustainable practices can help lessen these effects and open the door for a more ethical and environmentally friendly textile business in the future.

Mercerized cotton is still a popular option for producers and consumers alike because of its certain advantages and wide range of uses, exhibiting that quality and innovation can exist together.

2. How can we understand if cotton fabric is mercerized?
Ans: When cotton is mercerized, the material should have a rich, smooth shade, a subtle sheen, fewer wrinkles after washing or wearing, and easy ironing to get rid of creases.

3. Is mercerized fabric safe?
Ans: It is safe to use mercerized cotton. During the mercerization process, cotton is soaked in caustic soda and then completely cleaned of its substance.

Accordingly, there are no chemical agents left in the finished product. A safe and resilient material for a variety of applications, mercerized cotton is also stronger and more elastic than ordinary cotton. ‏

4. Why is it applicable only to cotton fabric? 
Ans: Cotton cloth enhances strength, lustre, and dyeability, making it the most popular material for mercerization.

Cotton fibers have a unique structure that makes them swell in an alkaline solution, leading to the process of mercerization.

Because they differ in their chemical composition and structure, other textiles like silk or polyester do not benefit from mercerization or respond to it in the same way.

5. Why mercerized cotton yarn is better than regular cotton yarn?
Ans: Compared to regular cotton yarn, mercerized cotton yarn is stronger, more glossy, better at absorbing dyes, produces less surface lint, and is more mildew-resistant. It also tends to get smaller and lose fewer sharp edges.

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Guest Author

This article is written by a guest author and reviewed, revised and edited by Tariq Bin Mutalib, Editor in Chief, TextileFact.com.

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