Mercerization

3.  Treatment of cotton fibre with concentrated
Sodium Hydroxide (19 to 26 % solutions).
 Objective
1. Destruction of Cuticle
2. Luster Effect.
3. Remove Dead Cotton.
4. Increase dyeing affinity (25-30%) and increase
Uniformity.
5. Strength
6. Dimensional Stability.

8. Mercerization
Chain
Mercerizing
Chainless
Mercerizing

9. Chain mercerizing is done on a range
equipped with tenter chains for tension
control. The range consists of a pad
mangle followed by a set of timing cans
and then a clip tenter frame. Fresh water
cascades onto the fabric to remove the
caustic soda as it is held tensioned in the
tenter frame, .

10. 1. Apply 22 to 25 % (48 - 54" Tw)
caustic at the pad mangle at 100 wet
pickup.
2. Pass fabric over timing cans. The number
of cans must correspond to the range speed
and provide at least one minute dwell time.
3. Clip fabric onto tenter chains and stretch
filling-wise while maintaining warp tension.

11. 4. Run fabric under cascade washers to remove
caustic. Keep under tension until caustic level is less
than 3% otherwise fabric will shrink in filling
direction
5. Release tension and continue
washing in open-width wash boxes,
to further reduce the caustic.
6. Neutralize with acetic acid in the next to last
wash box and rinse with fresh water in the last.

13. 1. Orderly orientation in the crystal Areas
2. Removal of fibre unevenness
3. Increasing the number of micropores
4. Unification of the pore size

14. 1. Goods should be dry entering the liquid caustic
impregnation unit. Need to get uniform and even
caustic pick-up through out the fabric.
2. Wet pickup must be at least 100 %.
3. For piece goods, a caustic concentration between 48 -
540 Tw should be maintained. Causticstronger than
540 Tw does not add to Mercerized properties whereas
below 480 Tw, the Mercerized fabric will have poor
luster and appearance.
4. Proper framing during the washing step is crucial.

15. Barium Number (AATCC Test Method 89)
It is based on the fabric‘s ability to absorb barium hydroxide. A two gram swatch of fabric
is placed in a flask containing 30 ml of a standardized 0.25 N barium hydroxide
solution. The fabric is stirred for two hours (to allow the barium hydroxide to be
absorbed by the fabric). A 10 ml aliquot is withdrawn and titrated with 0.1 N
hydrochloric acid to a phenolphthalein end point. The difference between the starting
concentration and the remaining concentration of barium hydroxide is the amount
absorbed by the fabric. The procedure is carried out on the fabric both before and
after Mercerizing and the barium number is calculated as shown below.
Amount Absorbed by Mercerized X 100
Ba No =
Amount Absorbed by Un Mercerized
Unmercerized fabric will give a barium number of 100 to 105. Completely mercerized
fabric will give a barium number of 150. Commercially treated fabrics fall in a range
between 115 to 130.

16. Yarns are Mercerized as continuous sheets in a
fashion similar to woven fabrics. Greige yarns enter
the caustic saturator and are held so they do not
shrink until the caustic has been washed out.
Afterwards, the yarns are dried continuously and
wound onto bobbins or spools. These conditions
will develop satisfactory luster, elasticity and dyeing
properties; however, if higher luster and strength is
desired, the yarns should be stretched beyond the
greige length during the process. Increase stretch,
however, reduces dye affinity and elasticity

17. 1. To produce lustrous, strong 100 % cotton sewing
thread.
2. To produce yarns for constructions that are
difficult to mercerize.
3. To produce yarns for special construction effects.
4. To produce yarns for blends containing fibers too
sensitive for mercerizing.
5. To provide more complete mercerization for luster
and strength.

18. Chainless mercerizing is practiced on a range where the
cloth is maintained in contact with rotating drums
virtually throughout the entire process. The tension
on the fabric depends on the friction between the
cloth and the surface of the drum. This results in
good control of length but limited control of width.
Bowed rollers are sometimes used to stretch the
width but they are much less effective when
compared with the clips of the chain Mercerizer.
Chainless Mercerizing is used on fabrics that cannot
be handled on a clip frame such as knits. Specialized
equipment has been developed for Mercerizing
tubular knit goods.

27. • Certain organic compounds possess the property of fluorescence which
means that they can absorb shorter wave length light and re-emit longer
wave-length. A substance can absorb invisible ultraviolet rays and re-emit
them within the visible spectrum. Therefore, a surface containing a
fluorescent compound can emit more than the total amount of daylight that
falls on it, giving an intensively brilliant white. Compounds that posses these
properties are known as OBA.
• When OBA treated fabric are exposed to UV light bulbs, the fabric glow in
the dark; thus conclusion can be drawn that the fabric is treated with OBA

29. • There are several classes of chemicals whose structure serve the
purpose. These structures have dye like properties and in
essence are colourless dyes. They can exhaust onto various
fibres.
• Anionic OBA’s will exhaust onto cotton, wool and silk.
• Cationic ones exhaust onto acrylic and certain polyesters.
• Nonionic exhaust onto all synthetics

30. • OBA,s are not a substitute for bleaching. They are used to obtain brilliant
market whites. These "white" whites can be obtained without over bleaching
and damaging the fiber.
• On cellulose, they have poor wash fastness but most commercial laundry
detergents contain OBA's so they are constantly replenished.
• Some OBAs have poor washfastness - some nonionics types have excellent
light fastness.
• Fiber producers can include OBA,s in their spinning process. These can have
excellent durability to both light and washing.

35.  The purpose of bio-polishing or bio-finishing is to get a soft handle and
attractive clean appearance of the fabric
 Cotton or cotton blend fabric contains small cellulosic protruding fibres or
microfibrils that make the surface of the fabric rough and fuzzy
 The problems associated with fuzz can also be eliminated by
 Singeing
 Applying silicon softner to soften the surface of the fabric
 By enzymatic bio-polishing

36.  Drawback of singeing
 Chance of fire hazards
 Drawbacks of silicon softners
 Reduces the water absorbency
 They are washed out and the fabric becomes rough again
 Enzymatic removal of fuzz is absolutely safe, efficient and permanent as it is
carried out in mild chemical and physical condition with accurate control
 Cellulase enzymes are usually classified by the pH range in which they are
most effective viz. acid stable, neutral stable and alkaline stable

37.  The enzyme cellulase degrades the cellulosic fuzz on the surface thus
increases the lustre and smoothness of the fabric
 Certain properties are however adversed
 Weight loss of the fabric
 Loss in fabric strength
 Recipe:
Enzyme dosage = 1 – 5% on fabric weight (depending upon the activity
of enzyme
Liquor ratio = 1: 5 to 1: 15
Time = 60 – 120 minutes (depending upon amount of hydrolysis required)
Temperature = 50 – 600C
pH = 4.5 – 5.5 (for acid stable cellulase)