Mercerization: Transforming Cotton Fibers
Mercerization
Mercerization
is
a
treatment
for cellulosic materials,
typically
cotton,
that strengthens them
and
gives them
a
lustrous
appearance.
It is
a
process in which
the fabric
is treated
with
cold
concentrated solution of Sodium Hydroxide
(NaOH).
The
process essentially
consist
of impregnation of
cotton
fabric
in NaOH
solution 25-35%
strength
for 30- 60
seconds at
temperature of 18-30
°C.
Objectives
of
mercerization:
To
improved
lustre
(shiny
).
To
increased ability
to absorb dye
and
moisture regain.
To
improved reactions
with
a variety
of
chemicals.
To
improved
strength/elongation.
To
improved
smoothness
and hand
feel.
To
improved stability of
yarn
form.
PROCESS SEQUENCES
OF
CHEMICAL
PROCESSING
G
r
e
y
f
a
b
r
i
c
D
e
s
i
z
i
n
g
S
c
o
u
r
i
n
g
B
l
e
a
c
h
i
n
g
D
r
y
i
n
g
M
e
r
c
e
r
i
s
i
n
g
D
y
e
i
n
g
P
r
i
n
t
i
n
g
S
o
a
p
i
n
g
&
D
r
y
i
n
g
F
i
n
i
s
h
i
n
g
F
o
l
d
i
n
g
&
P
a
c
k
i
n
g
S
i
n
g
e
i
n
g
Introduction
to
mercerization:
Mercerization was found by John Mercer in
1844
of
England,
who treated cotton fibers with
NaOH.
)
sometimes NH
3
, LiOH or KOH being
used
(
The
p
r
ocess
d
i
d
no
t
bec
o
me
p
o
p
u
l
a
r
unt
i
l
Horace.
A.
Lowe
improved
it
into its
modern
form in
1890
B
y
h
o
l
d
i
n
g
t
h
e
cott
o
n
du
ri
n
g
tr
e
atm
e
n
t
to
prevent it
from
shrinking,
Horace
Lowe
found
that the
fibre
gained
a
lustrous
appearance.
In the process of mercerization four factors are
considered:
NaOH conc., time, temperature
and tension.
This
mercerization
is
applicable
only
on
cellulosic
fibres
The
main
purpose
of
mercerization
is to
alter
the
chemical
and
physical
properties
of
the
fibre.
cotton
is held under specified tension
for
about
30 to
60
second
s with an
application of between
25
%
-35
%
caustic
soda
(NaOH) and
wetting agents
(used
to
facilitate
the
transfer
of the
NaOH
into
the
fibers),
at
18-30 °C
temperature. Then
the
fabric
is
neutralized
in
an acid
bath.
Caustic soda
solution
swells
cotton
fibers
breaking
hydrogen
bonds
and
weak
van
der
Waal
forces
between cellulose
chains.
The
expanded, chains
rearrange
and
re-orient
and when
the
caustic
soda
is removed
,
the
chains
form
new
bonds
in the
reorganized
state.
When done
tensionless,
the
cotton
fiber
swells, the cross
section
becomes
thicker
and
the
length is shortened.
the
fabric
becomes
denser,
stronger and more
elastic.
Under
tension,
The fibers
become
round
and
rod
like
in cross section
and the fiber
surface
is
smoothe
r
,
adding to fiber
luster
.
M
e
r
c
e
r
i
z
a
t
i
o
n
t
y
p
e
s
:
1
.
Full-mercerization
NaOH 28 - 32%
T
18
O
C
2
.
Semi-mercerization
NaOH 13 - 15%
C
o
n
d
i
t
i
o
n
s
o
f
M
e
r
c
e
r
i
z
a
t
i
o
n
1- Impregnation in NaOH for 50-60 s at
18
O
C or less.
2- Cloth must be desizing, so
NaOH can penetrate.
3- Addition of some wetting and penetrating agents.
4- Good tension of the cloth to its original dimensions
until washed , where the remaining
NaOH on fiber
must be around 7% only.
5- Avoiding any creases in the cloth.
6- Good adjustment of soda concentration used.
7- Good washing and neutralization with acid.
Mercerization
is
possible
-
after
desizing
-
after
desizing
and
scouring
-
after
bleaching
Mercerization
methods:
1
.
Slack Mercerization
(
treatment
without
tension
)
e.g. mercerization with
NH
3
2
.
Tension
Mercerization
(
treatment
under tension
)
e.g.
mercerization
with caustic
soda.
In
this
process
ammonia
is
penetrate
in
the
fiber
&
effect
the
crystalline
and
amorphous
region
of
the
fiber
and
swell
them
.
Aqueous ammonia can only be
disposed off
by
shipment to
fertilizer plants
or other non-textile
process that can use
this
liquid,
or,
it must be
recovered in an expensive distillation process for
further
reuse.
liquid
ammonia
treatment
is not so
popular.
1
-
A
mmonia
M
ercerization
(
Slack
Mercerization
)
:
Advantages
of
Liquid Ammonia
Mercerization
:
•
Improved
strength
(up to
90%
)
•
Enhance
luster
•
Better dye
ability
•
Stability
to laundering
and
greater thermal
resistance
W
hy
liquid
ammonia
treatment
is not so
popular
:
To
keep
liquid
ammonia
in
liquid
form it must
stored
below
33
O
C
.
It forms
explosive
moisture
with
air
When leakage in machine it is
highly
affected to
workers.
Procedu
r
es
:
Dipped
cotton
fabric
into
a
strong and cold
alkaline
solution such as
lithium
hydroxide, caustic soda, or
potassium
hydroxide.
The
fibers will
swell
and
shrink
while
still
impregnated
in
the
caustic
solution.
The
y
are
plac
e
d
under
t
en
s
i
o
n
while
in
this
swollen
state
and
then rinsed with
water.
T
he
a
l
ka
l
i
will
be
removed
an
d
a
permanent
round rod and
silk-like luster
will
result.
2
-
NaOH
M
ercerization
(Tension
Mercerization
)
:
P
hysical
C
hange
:
Breaking
of
old
bond
Effect
of
strong
caustic
soda
(Fiber
swollen
)
.
Improved
in
strength.
Improved
in
lusture
(under
tension
)
.
Change
in
cross
section
from
bean
shape
to
circular
shape.
Swell
and
opening
of
fibre
structure.
New
bonds
are
formed
upon
washing
off
NaOH.
Increase
in
the
number
of
OH
group.
The
reactions
that
take
place
in
mercerization:
Chemical
change:
Improvement
in
moisture
regain.
Improvement
in dye
uptake.
On
washing and
neutralization;
the
native
cellulose
I with
concentration
of NaOH
formed
cellulose
II.
Change in cross
section:
Effect
of alkali (NaOH)on cotton
fibres:
A
dvantages
of
M
ercerizing
The
mercerized fibers
were
able
to
absorb
more
water
,
and
therefore
absorb
more
dye.
colour
of the
dyed
cloth is
brighter
and
deeper.
it also
gives
the cloth a
better
resistance
to
multiple
washings
,
keeping
the
colours
bright
and
unchanged over
time.
Mercerization treatment
increases
strength,
smoothness,
and also
reduces
lint
(protruding).
It
also
increases
luster
and
affinity to
dyestuffs.
1
.
Chainless
mercerization:
This
method is also
called
roller
mercerization
.
The
machine
has
a
number of
stainless
rollers
and
rubber
r
o
ll
e
r
s
,
o
f
a
r
e
l
a
t
i
v
e
l
y
-l
a
r
g
e
di
a
m
e
t
e
r
tie
r
ed
z
i
g
z
ag
in
c
lose
contact to
each
other inside
a long
trough,
with the
lower
tier
designed
to submerge
in
alkaline
solution
for
mercerization.
This
type is
bound
to
limited
length
of
fabric.
Following
this initial
stage
of
alkali penetration
and
fabric
swelling,
a
similar device
is
used
for
the
removal
of
most
alkali
and
a
soaping
machine
for
further
removal
and
neutralization.
Types
of
mercerization’s
instrumentations:
2
.
Chain
mercerization
A clip
stenter
is used
for post-mercerization treatment,
in
which a width wise
tension
is applied then
most
alkali
is
showered
off
the
fabric
kept
on the
stenter,
followed
by
thorough
alkali
removal
and
neutralization
using
an
open-
width
washing
machine.
A
heavy
padding mangle
is
used
for
the
application
of
alkaline
solution in the 2 dip/2 nip
method,
with
sufficient
time
allowed for penetration
and
swelling
of
the
fabric
in a
timing
cylinder,
instead
of
undergoing an
operation
using
so
many
rollers
and so much solution
as
in
roller mercerization,
to ensure
reduced use of the
alkali.
Mercerization is a chemical treatment method primarily used on cotton fibers to enhance their strength, luster, and absorbency. The process involves treating the fabric with a concentrated solution of Sodium Hydroxide, resulting in various improvements such as increased dye absorption, enhanced stability, and smoother texture. Mercerization not only alters the physical properties of cotton fibers but also enhances their overall quality and appearance.
Download Presentation
Please find below an Image/Link to download the presentation.
The content on the website is provided AS IS for your information and personal use only. It may not be sold, licensed, or shared on other websites without obtaining consent from the author.If you encounter any issues during the download, it is possible that the publisher has removed the file from their server.
You are allowed to download the files provided on this website for personal or commercial use, subject to the condition that they are used lawfully. All files are the property of their respective owners.
The content on the website is provided AS IS for your information and personal use only. It may not be sold, licensed, or shared on other websites without obtaining consent from the author.
E N D
Presentation Transcript
Mercerization is a treatment for cellulosic materials, typically cotton, that strengthens them and gives them a lustrous appearance. It is a process in which the fabric is treated with cold concentrated solution of Sodium Hydroxide (NaOH). The process essentially consist of impregnation of cotton fabric in NaOH solution 25-35% strength for 30- seconds at temperature of 18-30 C. 60
Objectives of mercerization: To improved lustre (shiny). To increased ability to absorb dye and moisture regain. To improved reactions with a variety of chemicals. To improved strength/elongation. To improved smoothness and hand feel. To improved stability of yarn form.
PROCESS SEQUENCES OF CHEMICAL PROCESSING Grey fabric Singeing Desizing Bleaching Drying Scouring Mercerising Dyeing Printing Soaping & Drying Folding & Packing Finishing
Introduction to mercerization: Mercerization was found by John Mercer in 1844 of England, who treated cotton fibers withNaOH. )sometimes NH3, LiOH or KOH being used( The process did Horace. A. Loweimproved it into its modern form in 1890 Byholdingthecottonduringtreatmentto prevent it from shrinking, Horace Lowe foundthat the fibre gained a lustrousappearance. In the process of mercerization four factors are considered: NaOH conc., time, temperature and tension. not become popular until
This mercerization is applicable only on cellulosic fibres The main purpose of mercerization is to alter the chemical and physical properties of thefibre. cotton is held under specified tension for about 30 to 60 seconds with an application of between 25%-35% caustic soda (NaOH) and wetting agents (used to facilitate the transfer of the NaOH into the fibers), at 18-30 C temperature. Then the fabric is neutralized in an acid bath. Caustic soda solution swells cotton fibers breaking hydrogen bonds and weak van der Waal forces between cellulose chains.
The expanded, chains rearrange and re-orient and when the caustic soda is removed , the chains form new bonds in the reorganized state. When done tensionless, the cotton fiber swells, the cross section becomes thicker and the length is shortened. the fabric becomes denser, stronger and more elastic. Under tension, The fibers become round and rod like in cross section and the fiber surface is smoother, adding to fiber luster.
Mercerization types : 1. Full-mercerization NaOH 28 - 32% T 18OC 2. Semi-mercerization NaOH 13 - 15%
Conditions of Mercerization 1- Impregnation in NaOH for 50-60 s at 18OC or less. 2- Cloth must be desizing, so NaOH can penetrate. 3- Addition of some wetting and penetrating agents. 4- Good tension of the cloth to its original dimensions until washed , where the remaining NaOH on fiber must be around 7% only. 5- Avoiding any creases in the cloth. 6- Good adjustment of soda concentration used. 7- Good washing and neutralization with acid.
Mercerization is possible -after desizing -after desizing and scouring -after bleaching Mercerization methods: 1. Slack Mercerization (treatment withouttension) e.g. mercerization with NH3 2. Tension Mercerization (treatment under tension) e.g. mercerization with causticsoda.
1- Ammonia Mercerization (SlackMercerization): In this process ammonia is penetrate in the fiber & effect the crystalline and amorphous region of the fiber and swell them. Aqueous ammonia can only be disposed off by shipment to fertilizer plants or other non-textile process that can use this liquid, or, it must be recovered in an expensive distillation process for further reuse. liquid ammoniatreatment is not so popular.
Advantages of Liquid AmmoniaMercerization: Improved strength (up to 90%) Enhance luster Better dye ability Stability to laundering and greater thermal resistance
Why liquid ammoniatreatment is not so popular : To keep liquid ammonia in liquid form it must stored below 33OC. It forms explosive moisture with air When leakage in machine it is highly affected to workers.
2-NaOH Mercerization (Tension Mercerization): Procedures: Dipped cotton fabric into a strong and cold alkaline solution such as lithium hydroxide, caustic soda, or potassium hydroxide. The fibers will swell and shrinkwhile still impregnated in the caustic solution. They are placed under tension whilein this swollen state and then rinsed withwater. The alkali will be removed and a permanent round rod and silk-like luster willresult.
Physical Change: Breaking of old bond Effect of strong caustic soda (Fiber swollen). Improved in strength. Improved in lusture (under tension). Change in cross section circular shape. Swell and opening of fibre structure. New bonds are formed upon washing off NaOH. Increase in the number of OH group. from bean shape to
Chemical change: Improvement in moisture regain. Improvement in dye uptake. On washing and neutralization; the native cellulose I with concentration of NaOH formed cellulose II.
Change in cross section: 1. Cross section of cotton beforemercerisation 2 -5. swelling process in 18% NaOH 6. Rinsing process after swelling 7. Final state
Advantages ofMercerizing The mercerized fibers were able to absorb more water, and therefore absorb more dye. colour of the dyed cloth is brighter and deeper. it also gives the cloth a better resistance to multiple washings, keeping the colours bright and unchanged overtime. Mercerization treatment increases strength, smoothness, and also reduces lint (protruding). It also increases luster and affinity to dyestuffs.
Types of mercerizationsinstrumentations: 1. Chainless mercerization: This method is also called roller mercerization. The machine has a number of stainless rollers and rubber rollers, of a relatively-largediameter tiered zigzag in close contact to each other inside a long trough, with the lower tier designed to submerge in alkaline solution for mercerization. This type is bound to limited length of fabric. Following this initial stage of alkali penetration and fabric swelling, a similar device is used for the removal of most alkaliand a soaping machine for further removal andneutralization.
2. Chain mercerization A clip stenter is used for post-mercerization treatment, in which a width wise tension is applied then most alkali is showered off the fabric kept on the stenter, followed by thorough alkali removal and neutralization using an open- width washing machine. A heavy padding mangle is used for the application of alkaline solution in the 2 dip/2 nip method, with sufficient time allowed for penetration and swelling of the fabric in a timing cylinder, instead of undergoing an operation using so many rollers and so much solution as in roller mercerization, to ensure reduced use of thealkali.
