Mercerization is a chemical treatment for cotton fibers that enhances their dye affinity, tensile strength, and lustre by altering their shape and molecular structure. The process includes factors such as time, temperature, twaddle (concentration of NaOH), and tension, which impact the fiber's properties. While beneficial for textile quality, sodium hydroxide used in mercerization poses environmental hazards necessitating proper wastewater management.

1. Mercerization

2. Presented by: Presented to:
Md. Sahidul Islam
Name:Mithun Dev Nath Lecturer
ID:2018000400019
Department of Textile Engineering
Southeast University
Date of Submission:25/09/2020

3. Mercerization
Mercerization, in textiles, a chemical treatment applied
to cotton fibres or fabrics to permanently impart a
greater affinity for dyes and various chemical finishes.
Mercerizing also gives cotton cloth increased tensile strength,
greater absorptive properties, and, usually, a high degree of
lustre, depending on the method used.

4. To improve the luster
To improve the strength
To improve the dye uptake and
To improve water absorbency
Object

5. Change due to mercerization
 Round surface can reflect the light better than a rough surface. Due to mercerization cotton shape
become round.
 Luster is a result of light reflection off a surface. The more glass like the surface, the better the luster
 Yarn has a very fine covering of tiny fiber ends (fuzz). This fuzz is removed by passing the yarn (or fabric)
through a controlled heated atmosphere termed singeing (gas fired in the past, electric more currently)
resulting in a cleaner surface.
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6. What happens to cotton during
Mercerization
 Swelling of the fibre takes
place.
 the cross section ,like
kidney shaped becomes
circular or oval-shaped,
thus enhancing the luster
 Shrinkage of length wise.
 Strength improved
 Cellulosic chains gets
rearranged .

7. MICROSCOPIC VIEW

8. WHAT HAPPENS INSIDE COTTON
 After swelling NaOH thoroughly penetrates amorphous phase
of thefibre,
 reaction between the alkali and the micelle occurs
 completing the generation of alkali celluloseI.
 At higher concentrations, the hydrate volume is smaller.
 Hydrates cause lower swelling but able to penetrate the
crystalline phase and change the crystal structure.
 Such changes are capable of inducing important structural
modifications in fibre structure.

9. Conversion of Cellulose
• The native form of cellulose which occurs in cotton and other natural cellulosic fibres,
is known as cellulose I.
• It has it unique crystal diffraction pattern (monoclinic). It is a thermodynamically less
stable form of cellulose.
• When cellulose in converted to regenerated cellulosic fibres like viscose, dissolution
of cellulose is an intermediate step.
• During regeneration, it gets converted to a different crystalline form, known as
Cellulose II.

10. CHEMICAL REACTION

11. EFFECT OF MERCERIZATION
1.Fibre level
2.Molecular level
3.Chemical change
4.Mechanical change

12. Change due to mercerization
A. Fiber level
1. Swelling
2. Cross sectional morphology changes from beam shape to round shape.
3. Shrinkage along with longitudinal direction.
B. Molecular level
1. Hydrogen bond readjustment
2.Orientation (parallelization) of molecular chains in amorphous region along the direction of fiber
length.
3. Orientation of the crystallinity in the direction of the fiber length.
4. Increased crystallinity
C. Chemical Changes
1. Increased rate of reaction on hydrolysis and oxidation
2. Liberation of heat during the caustic treatment.(heat of sorption and heat of reaction)
3. Increase in the alkali absorption.
4. Increase in the absorption of iodine. Changes during mercerizing process

13. Effects of the mercerization of cotton fabric

14.  According to the form of the tension
 A. tension mercerization
 slack mercerization
Mercerization are Two Types:

15. 1) Tension Mercerization
• The purpose of mercerization is to increase luster of Cotton fibers
• The fiber untwists and swells, lumen becomes rounder in cross-section and it gains luster.
• Dye affinity and chemical reactivity increase. Fabric becomes stronger and smoother.
1) Slack Mercerization
• Not as lustrous as tension method
• Elongation and recovery properties improve and thus have been used to produce comfort
• stretch garments and fabric bandages, which need to conform to body shapes.

16. Factors of mercerization:
There are 4 factor which are called 4T. They are-------
 Time
 Temperature
 Twaddle
 Tension

17.  Time: The time of the mercerization is 30 to 60 seconds. If the
mercerization takes longer time it will not improve the quality but if
the time is limited to 30 s the good quality in appearance can be
achieved .
 Temperature: The optimum temperature of mercerization ranges
between 18 -20°c
 Twaddle (conc. of NaOH) :the concentration of NaOH is 48° Tw
to 54° Tw
 Tension: Tension will be applied both in warp and weft of the fabric

20. Mercerization is done
- on greige goods
- after desizing
- after desizing and scouring
- after bleaching
- after dyeing.

21. 1. Larger dyeing affinity
2. Larger dimensional stability of thearticles
3. Increasing of thelustre
4. Increasing of the tensilestrength
5. Better covering of dead and/or mossycotton
6. Improving to the touch
Advantages

22.  We know about the toxicity profile of sodium hydroxide, which is considered one
of the building blocks of chemistry. It’s a very powerful alkali. It’s used in industry
in a broad range of categories: chemical manufacturing; pulp and paper
manufacturing; cleaning products such as drains, pipe lines and oven cleaners ;
petroleum and natural gas; cellulose film; and water treatment as well as textiles.
 The US Food and Drug Administration (FDA) considers sodium hydroxide to
be generally safe, and recognizes it as not being found to pose unacceptable
dietary risks, though it is generally only used on food contact surfaces rather than
in foodstuffs.

23. Cont…
The Barium Activity Number is given as:
BAN = (B-M) / (B-C)*100
Where B = Volume of HCl (ml) required for blank titration
M = Volume of HCl (ml) required with mercerized cotton
C= Volume of HCl (ml) required with un-mercerized cotton
For completely mercerized cotton the value of BAN is around 155 and for semi
mercerized cotton it varies in between 115 and 130.

24.  The chemical is toxic to wildlife, and the EPA requires that effluent containing
NaOH not be discharged into groundwater.
 Because sodium hydroxide falls in the group of chemicals (salts) which are by far
the most often used in textile processing, the sheer volume of NaOH used by
the textile industry is important to recognize. Usual salt concentrations in
cotton mill wastewater can be 2,000 – 3,000 ppm, far in excess of Federal
guidelines for in- stream salt concentrations of 230ppm.
 So treatment of effluent is very important, as prevention is the only reasonable
alternative to solve the environmental problems associated with this hard-to-treat,
high volume waste.

25. Thankyou