Long Way Education

By Eman Abdallah kamel

Eman is a writer and engineer. She received her bachelor’s degree in textile sciences from the Faculty of Applied Arts.

In this article, you will learn the definition of mercerization, the process, the chain and chainless mercerizing machine, and the benefits of mercerization.

Definition

Mercerization is the process of treating cellulose fibers, especially cotton, with a strong caustic alkali solution for a short period at low or high temperature to improve luster, dyeability, and other properties.

Mercerization changes the chemical structure of cotton fiber, causing its cell wall to swell, increasing surface area and reflectivity.

History

English scientist John Mercer invented this process in 1844, treating cotton with 20-30% sodium hydroxide solutions and then washing it. Mercer observed that this treatment shrank the fabric and increased its tensile strength and attractiveness to dyes. Mercer considered increasing the dyeability of the fabric to be the most important technical aspect.

Pre-Mercerization Operations in Wet Processing

1. Entry of grey fabric,
2. Singeing and desizing,
3. Scouring and bleaching.

Process

• An effective mercerization process requires the use of wetting agents.
• Caustic soda concentrations of 20% to 26%.
• Soak the fibers in a dilute sodium hydroxide (NaOH) solution. Different degrees of modification are achieved by varying,

1. The concentration of the alkali solution,
2. The temperature,
3. and the treatment duration.

• Treatment with sodium hydroxide destroys the helical structure of cellulose, forming alkali cellulose, which is converted to cellulose hydrate upon alkali washing.

Did you know?

Mercerizing denim is typically performed after the weaving process. It can be used to achieve ring dyeing, which keeps the dye on the surface of the yarns or fabrics, preventing it from fully penetrating the fibers. In addition to increasing the luster of the fabric, mercerizing also improves its durability.

Fabric Mercerization Types

• Chain Mercerization.
• Chainless Mercerization.

1. Chain mercerization machine: A range with stenter chains for tension control is used for chain mercerizing. A pad mangle, a set of timing cylinders, and a clip stenter frame make up the range.
2. Chainless mercerization machine: During chainless mercerizing, the cloth is kept in proximity to revolving drums for the duration of the procedure. 

Tools of the Fabric Mercerizing Machine

The fabric mercerization machine consists of:

• Inlet J-Scray: Utilizing a compensator, pressure roller, and tensioner roller, this device gathers the fabric during batch changes to prevent machine stoppage.
• Impregnation Unit: The two compartments of the impregnation unit are both filled with a caustic soda solution at the proper concentration. The cloth is dipped into the caustic soda solution, and the excess caustic is then squeezed out.
• Timing Rollers: They consist of a series of steel rollers. The fabric passes under tension through these rollers, causing a reaction between the fabric and the caustic soda.
• Stenter Unit: It has a spraying unit and a chain drive.

• Wash and Neutralization Chamber: This chamber uses hot water to remove excess caustic soda from fabric. In the neutralization chamber, the fabric’s pH is corrected by adding mild acetic acid and then washing away the excess acid.
• Vertical Drying Assembly: It has cylinders made of stainless steel and Teflon. Steam passes through the cylinder. The fabric is dried as it moves over the cylinder.
• Output Unit: It is used to collect fabric during batch changes to prevent machine stoppages and produce a defect-free batch of fabric.

Machine Mercerization Steps

The mercerization machine’s steps include:

1. 200–220 gpl of caustic is added at the pad mangle while it is 100% wet.
2. Fabric is passed over timing cylinders.
3. The number of cylinders must match the speed range and provide at least one minute of stopping time.
4. Pin the fabric onto the stenter chains and then stretch it towards the weft.
5. To remove caustic materials, run the cloth under the spray washers.
6. Continue washing in open-width wash boxes to further lower the caustic content after releasing the tension. Dry the fabric after neutralizing it with acetic acid.

Mercerization Benefits

• Mercerization improves the surface adhesion properties of fibers by removing natural and synthetic impurities.
• Mercerization alters the crystalline form of cellulose through a complex solid-state mechanism, resulting in an increase in the amount of amorphous cellulose at the expense of crystalline cellulose.
• Mercerization also leads to fiber fibrilization, i.e., the fragmentation of the composite fiber bundle into smaller fibers, increasing the effective surface area available for contact with the wet matrix.
• Mercerization significantly enhances the reactivity of cellulose.

Sources

• Textilescommittee.nic.in/.pdf
• Sciencedirect.com/mercerization.

©Eman Abdallah Kamel, 2025

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