Processing of wool

1. Physical and
Chemical
Properties of
Wool

2. General Properties of True Wool:
• Elastic and hygroscopic (25 % of weight)
• Inflammability: slower to burn, and on
burning, it gives off a pungent odour and
forms a bead when burning ceases
• Retains warmth (insulator)
• Devoid of stiff medulla and central core of
hard cells.
• Fine enough for production of soft pliable
yarn.
• Natural felting property Wool's scaling and
crimp make it easier to spin and felt the

3. Physical properties of Wool
 Fleece Density- Number of fibers per unit area on skin. Fine
wool breeds such as Marino has more fleece density than
coarse wool breed.
 Diameter- Measured in micron to indicate wool fiber
fineness.
 Fiber cross section-It is circle to oval
 Crimp-The waviness per cm in wool fiber which speaks of
the qualitative fineness.
 Specific gravity-It is 1.304 in dry non-medullated wool.

4. Refractive index -It varies in between 1.553 to 1.555.
Lusture –
Ability of wool to reflect light.
Wool with lustre, when dyed, has a brighter appearance
than wool without lustre.
Coarse wool with fewer scales has more lustre than fine
wool because of smoothness of fibre
Sheen or gloss. It depends on structure of fiber surface, size
and straightness of the fiber.
Electrical conductivity- wool is good insulator to current.
Thermal conductivity-Wool does not support fire.

5. Moisture regain- Weight of water in wool as percentage of dry
weight.
R = W/D* 100 ; W= weight of water, D = Oven dry weight
Moisture content- It denotes weight of water present in wool as
percentage of total weight.
M = W/W+ D *100
Moisture content of greasy wool is less than that of scoured wool.
Coarse wool has more affinity to water.
Moisture relation-The electrical properties varies with moisture
content.
Moisture swelling-It represents swelling in fiber diameter due to
absorption of moisture.

6. Chemical properties of Wool
 Chemically wool is approximately 50 % carbon,
22 to 25 % oxygen, 16 to 17 % nitrogen, 7 %
hydrogen and 3 to 4 %sulfur.
 Composed almost totally of amino acids
 Wool is described as 100% protein and is
classified as an insoluble, sulfur containing
protein called keratin.
 Wool becomes yellow if kept in warm humid
places.

7.  Action of heat
• Wool burns slowly and forms a porous brittle
mass of carbon which emit disagreeable fume
like that of smell of burning of hair or feather.
• Wool fabrics become plastic in moist air at 100
0C but can be easily moulded in to shapes
which are retained on cooling.
• It gives up all moisture when heated to 100-
1500C and produces a rough harsh brittle
substance with less strength.
• Despite re-absorption potential of moisture
original strength, softness and elasticity is not
restored completely.

8. • Dry wool at higher temperature become discoloured and
decomposes.
• Keratin decomposes readily to ammonia at 130 0C.
• Gases having sulfur are given off at still higher
temperature.
• Gases like ammonia, hydrogen, water, carbon dioxide,
carbon monoxide and carbon are formed in absence of air
at still further high temperature.
 Action of water
• Wool is neither soluble in cold nor hot water.
• Breaking up of wool macromolecules occur on continued
boiling with water which causes decomposition.
• Wool softens and losses strength on soaking in cold or
hot water but drying restores it to some extent.
• Wool acquires increased affinity for dyes on exposure to
action of steam at high temperature.

9.  Action of acids
• No harm occurs to wool in cold or boiling dilute solution of
acids.
• Wool absorbs the solution of acid and that is not
removable by washing with water as amino group acts as
site for holding acids in wool.
• Wool acquires more affinity for acid dyes but decreases its
basic dyes affinity when treated with an acid especially
sulfuric acid.
• Colour of wool become light yellow on treatment with nitric
acid and this colour reaction is useful in identification of
animal fibers.
• Slow dissolution of wool occurs in concentrated inorganic
acids.

10.  Action of alkalis
• Wool is comparatively sensitive to alkalis.
• Complete destruction or dissolution of wool occurs when
boiled with 5% solution of caustic soda even for few minutes
because amino group breaks as a result of hydrolysis.
However, dilute solution of ammonia does not harm wool but
concentrated solution at higher temperature harms wool.
• Wool needs great care during laundering for prevention of
fabric shrinkage.
• Wool fabrics absorb and hold odour more than other fabrics
which can be removed by controlled laundering but not
effectively.
• Wool garments contain more number of bacteria than any
other garment from other textile fibers in similar use and dry
cleaning kills 90% of such germs with elimination of health
hazard.

11. Mechanical properties
Wool fiber undergoes considerable strain in manufacturing
process as carding, combing and spinning. The ultimate
strength of the wool will achieved is influenced by:
 Poor nutrition cause tenderness and break in fibers.
 Photochemical action of light on very open type fleece on the
back wool of animal weakens it.
 Breed and strength differences of wool fiber are associated
with difference in diameter, on application of tension or
constant rate of loading to a wool fiber in water or moisture.
 Extension of fiber proportional to load as per hooks.
 Moving up of “Easy Stretching Zone” from 30-100%
extension in boiling water or steam owing to wet wool fiber
being much easier to stretch than dry wool fibers.

12. • Complete recovery of 30% stretched fiber due to
reversibility of hydrogen bonding transformation in water.
• Incomplete reversibility of fiber extension in post yield
region of load extension curve due to breakage of
disulfide bonds
• Positioning of fibers made permanently with fixing fluid
on woolen fabrics (sodium bisulphate solution,
ammonium trioglycollate).

13. Speciality Fibre
• From goat and camel
Goat Family-
Angora goat- Mohair
Cashmere goat- Pashmina fibers
Common goat- Goat hair

14. Camel
• Dromedary/Bactrian camel –produces camel
hair

15. Llama family
Guanaco-produces fiber
Llama- Llama hair
Vicuna- Vicuna wool
Alpaca- Alpaca hair

16. Mohair
• Long fiber covers of Angora goat originated in Asia
Minor.
• Angora goat - in province of Angora in Turkey
• Elimination of Kemp fiber is an important factor for
improvement of Angora goats.
• More desirable and stronger than Kashmir
• Fineness bearing with age.
• Kid Mohair forms better fiber and yarn than advent
mohair.

17. Physical Properties of Mohair
• Clean yield- 81- 83%
• Fibre diameter- 22.7- 23.3 micron
• Staple length- 7.9- 8.2 cm
• Medullation- 5.5- 6.2
• Kemp- 4.5- 7.6

18. Pashmina Fibre
 Softest, finest and costliest animal fiber known in the
textile industry
 Produced by fine under coat of Capras hircus (Pashmina
goat) originated in Asia
 Parent breed is the Kel of Kashmir and extend high
mountainous region of Asia, Himalayan region and outer
magnolia
 Colour- white or brown
 Diameter- 13 to 18 micron
 Length- 3-12 cm
 % Hair- 10- 40%

19. Pashmina
• Obtain by combing, clipping mohair, shearing per sheep.
• Have cylindrical scale and longer than wool
• Yield increases from 1-4th fleeces yield and declined there after.
• Sub zero temperature induces production of pashmina fibers.
• Male produces more pashmina than female
• 3 items more insulating property than wool.
• Short soft and non –medulated.
• Weaker than mohair and wool.
• Pashmina wears are less durable than woolen fibers.

20. PROCESSING OF WOOL
• Wool shearing: - The process of removal of
wool from sheep or harvesting of wool from the
body of the sheep is known as shearing.
• Shearing is strictly a seasonal job and can be
performed any time except during winter.
• The practice of shearing sheep is not uniform,
which may vary according to agro-climatic
condition of the region.
• Sheep are normally sheared twice or thrice a
year.

21. Methods of shearing
1. Hand shearing
2. Mechanical shearing by power operated
shearing machines
3. Chemical shearing: The method of feeding
sheep 24 mg Cyclophosphamide (CPA) @ per
kg body weight of sheep. After 12 days of
feeding of the chemical, wool is removed within
3 days starting from 12th day after drug
administration.

22. 1. Tagging: - Tagging is a practice that improves
the appearance of wool clip. It consists of
removing the tags and dung locks especially in
the sample obtained from hindquarters of the
animal.
2. Wool grading or Wool classing:- The quality
of wool differs in many respects as described in
previously.

23. 3. Sorting: - Raw wool brought to the factory is
sorted first as per the requirement. This is an
advanced step requiring more skill and is
different from classing or grading.
4. Opening and dusting: - It is the process of
opens up the clumps of fibers into individual
staples and at the same time delivers a uniform
quantity of opened stock to the scouring train.
This facilitates the proper penetration of the
scouring liquor into the wool fibre, rendering the
scouring more uniform and throughout. It also
reduces cost by saving on soap alkali scouring
liquor.

24. 5. Scouring: - It is washing the wool in warm
water and in detergent solutions for the removal
of impurities in raw wool.
6. Burr picking and carbonizing: - Wool contains
a large or small amount of burr.
• If the burrs are not removed they cause
considerable difficulty in the manufacturing
process and may damage card, clothing and
combs.
• The chemical removal of burr is known as
carbonization. immersing the wool in a solution
of sulfuric acid (H2SO4) that remove the
vegetable matter present in the wool.

25. • 7. Oiling: - The wool is lubricated with oil
emulsion to minimize the breakage of fibre
during carding, reduce the fly waste and
static electricity in carding and increase
cohesion of the fibres in loose silver, thus
facilitating drafting and spinning. Mostly
non-ionic mineral emulsified oils are used
in the strength of 3-5 per cent of wool
weight.
• In India mahua oil (for carpet industry)
emulsified with crude soap is extensively
used.

26. 8. Carding and spinning: Carding is done
to further open the wool, straighten the
individual fibre and remove natural
impurities and delivering it in a convenient
form for spinning. Three type of carding.
a. Woolen carding
b. Worsted carding
c. Weaving
9. Dyeing and finishing:- It forms the final
process in the preparation of wool ready to
market.

27. Scouring
• Scouring is the process of removal of impurities
in raw wool. It is accomplished by aqueous
scouring (detergent method) process or by
solvent degreasing (ether or benzene) method.
• Scouring is accomplished in a series of vats or
bowls (3-6) through which the wools propelled
by mechanical rakes with intervening
squeezers.
• The squeezed stock is dried through specially
constructed dryers.

28. Vegetable matter content
 Hand picking: Vegetable matter is separated by hand, is the most accurate but is
also the most time consuming. Because its slowness the method is not suitable
for large scale testing.
 Carbonizing : Chemical removal of burr is known as carbonization. It is done by
using acids such as sulphuric or hydrochloric acid and or by salts such as
aluminum chloride which produces acid when heated.
 Comparison: Scoured sample is immersed in a liquid of the same refractive index
as wool (1.555). A suitable liquid is made from a mixture monochloronaphthalene
and a petroleum distillate. The sample is illuminated from below by a special
apparatus called Transparizer and various kinds of vegetable matter become
apparent.
 Caustic soda: most rapid and most commonly used method for vegetable matter
content determination, in which the wool is dissolved in boiling NaOH. This
method requires the use of correction factors, since the boiling caustic soda
dissolves a variable quantity of lignin and other components in the vegetable
matter.