Mercerization is a process that increases the luster of cellulosic fibers like cotton. There are two types: tension mercerization increases luster the most by swelling and rounding the fiber's cross-section as it is stretched in a caustic solution. Slack mercerization improves elasticity for fabrics that need to conform to the body. The goals of mercerization are to increase luster, strength, stability, dye uptake, and elasticity. It involves impregnating relaxed fibers in caustic soda, stretching them while soaked, and washing while maintained in a stretched state to cause chemical and physical changes that modify the fiber structure and properties.

1. (Affiliated by University of Dhaka)

2. MERCERIZATION

3. MERCERIZATION
Mercerization is a process applied to cellulosic fibers –
typically cotton (or cotton-covered thread with a polyester
core) but hemp and linen can be mercerized also – to
increase luster. It is done after weaving (in the case
of fabrics) or spinning (for yarns or threads).

4. TYPES OF MERCERIZATION
1. Tension Mercerization.
• The purpose of mercerization is to increase luster of cotton fibers.
• The fiber untwists & swell, lumen becomes rounder in cross-section and it get luster. Dye
affinity and chemical reactivity increase. Fabric becomes stronger and smoother.
2. Slack Mercerization
• Not 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.

5. OBJECT OF MERCERIZING
• To obtain stable dimension, durable shines, promote
absorption of dyes evenness. Good mercerize process
can reduce the dye consumption upto 30%, Suitable
varieties: cotton and blends, Apparel fabrics including
yarn dyed fabric, home-textile fabrics and etc.

6. PURPOSE OF MERCERIZING.
• Improving luster (silky look, in tension mercerization only).
• Improving tensile strength.
• Improved dimensional stability.
• Increasing uniformity of dyeing & improving color yield (savings
in dyestuff).
• Improving Elasticity or Stretch material (in slack mercerization
only).

7. MERCERIZING STEPS
a. Impregnation of the material in in relaxed state,cold caustic
solution of required strength and wettability..
b. Stretching while the material is still impregnated in the caustic
solution.
c. Washing off the caustic soda from the material while keeping
the material still in the stretch state.

8. CHANGES DURING MERCERIZING PROCESS
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.

9. TYPICAL MERCERIZING CYCLE:
1. Loading of material on the rollers in rest position.
2. Lowering of rollers
3. Caustic tray movement
4. Pre tensioning
5. Free shrinkage
6. Lye tensioning
7. Squeezing
8. Washing tray movement
9. First wash and tensioning
10. Second wash
11. Third wash
12. Final wash
13. Squeezing
14. Lifting Of Rollers
15. Unloading the hanks.

10. MERCERIZING OF COTTON FABRIC
Fabric after Scouring
and Bleaching process
Padding in alkaline
liquor
Washing
Neutralization in acid
solution
Washing
Drying

15. MERCERIZING IN SIM GROUP:
Parameter:
Steam cylinder= 20
Temp= 100°C
Pressure = 2-2.5 pa
1th pressure = 0.21 mPa
Padder= 0.21mpa
2nd pressure= 0.31 mpa
Padder= 0.24mpa
Caustic soda = 1L on 766gm= 50 boom
18 boom= 3000L
Sometime they add
 mercerize oil
 acetic acid
 wetting agent
Scouring caustic= 30-50g/l