Mercerisati
on

About Mercerisation
• Mercerization is the treatment of
cotton with a strong caustic
solution.
• This is performed on yarn or
fabric, both woven and knits.
Tension may or may not be used.
Inventor John Mercer

Purpose
• Lustre is increased
• Improves absorption, increase in dye
affinity and yield
• Improves breaking strength (improved up
to 20%)
• Improves dimensional stability
• Improves chemical reactivity
• Improves fabric smoothness
• Covers immature cotton fibers

When to Mercerize
•In Greige
•Any step during
preparation
•After bleaching

Observable Changes or
Properties of Mercerised Cotton
• Deconvolution
• Lumen disappears
• Fibers become rounder,
smoother, and more uniform
• When cotton is mercerised slack
(without tension), it shrinks and
shows good elastic properties

Cotton

Unmercerized vs. Mercerized
Fibers

The mercerisation process
• NaOH Conc. : 18 to 22% (55o to 65 o Tw)
• Time of contact : 60 to 75 seconds
• Temp :27o
C
• Shrinkage : Controlled by stenter frame
by stretching back to original width
Caustic concentration
– Lower- Less luster
Time < 30 sec. Incomplete
mercerization

• Yarn stage
–yarn-mercerising machine
• Fabric (continuous mercerisation
process)
–chain mercerisation machine
–chainless mercerizing machine
–chainless-padless continuous
mercerising machine
Machines used

Fixed Roller
Movable Roller
Perforated pipe for
spraying alkali/wash
water
Pointer and
scale to set yarn
tension
A batch of hank yarn
Tray
Rubber Squeezer Roller

Mercerisation of Cotton
Fabric
• 1. Chain mercerising machine – here the
cloth is first allowed to shrink in the
caustic soda solution and subsequently it
is stretched.
• 2. Chainless mercerising machine – in this
case tension is applied to the fabric
during alkali impregnation itself, so the
fabric is not allowed to shrink.
• 3. Pad-less chainless mercerising
machine

Chain Mercerising
Process
1. First alkali impregnation mangle
(alkali concentration = 35-45° Tw;
temp 40° C; time 60-75 sec)
2. Second alkali impregnation mangle
(alkali concentration = 55-65° Tw;
temp 27° C; time 60-75 sec)
3. Stenter (Stretching and washing unit)
4. Recuperator (Steam treatment to wash off
residual alkali)

A Schematic Representation of the Chain
Mercerising Process
1. First alkali impregnation mangle
(alkali concentration = 35-45° Tw; temp 40° C;
time 60-75 sec)
2. Second alkali impregnation mangle
(alkali concentration = 55-65° Tw; temp 27° C;
time 60-75 sec)
3. Stenter (Stretching and washing unit)
4. Recuperator (Steam treatment to wash off
residual alkali)
5. Hot water wash
6. Souring (with dilute mineral acid)
7. Cold water wash
8. Mercerised fabric
3 5 6 874
GREY FABRIC
1 32

Chain Mercerising Process
5. Hot water wash
6. Souring (with dilute mineral
acid)
7. Cold water wash
8. Mercerised fabric

Stenter – Stretching and
Washing Unit
Fabric stretch zone in
stenter
Fabric counter -
current wash
zone
Merceris
ed,
washed
fabric
WATER
Flow
Fabric Movement
Chain I
Chain
II
Clips
Clips
A basic diagram of a stenter unit in a chain mercerising
machine (only some clips are shown)

Disadvantages of the Chain
Mercerising
• Only certain widths of fabric
limited to the stenter width can be
used.
• The stenter unit is very long and
occupies a large amount of
space.

Chainless Mercerising
Machine
• Impregnating unit
• Expanders or stretching rollers
• Recuperator
• Neutralising and washing unit
• The functions of units (a), (c) and (d) and
the conditions of mercerisation are the
same as those for the chain mercerising
machine. Only the stretching process (b)
is different in this case.

Advantages of the Chainless
Mercerisation Machine
• The floor space required is less compared
to chain mercerizing.
• Lightweight fabric can be mercerised
easily. (This is difficult in a chain mercerising
machine.)
• There is no difficulty in mercerising cloths of
different widths.
• No distortion of material takes place. So
checked fabrics can be processed on this
machine without distortion of the design.
• Two or three superimposed fabric pieces

Pad-less Chainless
Mercerisation
• It is designed to mercerise fabric
under tension
• it does not require the use of the
following units.
–1) Impregnating mangles
–2) Chain system (stenter)

Pad-less Chainless
Mercerisation

Important Process
Sequence
• Impregnating Section
• Washing
• Recuperator

DYEING
• The application of color to the whole body
of a textile material with some degree of
fastness.
There are two ways of adding colour to a
textile substrate
– Dyeing
Dyeing completely covers the textile
with colour
--Printing.
adds colour to the fabric surface in
discrete or distinct places.

Materials Dyed
• Fibers
– Stock dyeing
– Dope dyeing
• Yarns
– Skein dyeing
– Package dyeing
– Beam dyeing

Materials Dyed
• Fabrics
– Piece dyeing
– Printing
• Roller –application, resist, discharge
• Flat Screen
• Rotary
– Tie Dyeing
• Garments
– Garment dyeing

Material used
• Dyes and Pigments
–The substances used to colour
textiles can be classified as
dyes or pigments, the
differences between which are
listed in the table below.

Exhaustion Dyeing