This document provides an overview of man-made fiber formation and regenerated fibers. It discusses the basic principles of fiber manufacturing including converting the fiber-forming substance into a fluid and extruding it through spinnerets. Melt spinning and solution spinning methods are described. Regenerated fibers like viscose rayon and cellulose acetate are discussed, including their manufacturing processes. Properties and uses of various fibers like polyester, nylon 6, and nylon 6,6 are also summarized.

1. CHAPTER FOUR
LECTURE 4 ON
Man- Made Fiber Formation and Regenerated Fibers.
BAHIR DAR UNIVERSITY (EiTEX)
By: Bademaw Abate(Lecturer)

2. INTRODUCTION
➢ Textile fibers are made by man starting from various kinds of raw
materials. The starting raw materials for fiber making can be natural and
synthetic polymers.
➢ Accordingly man- made fibers are classified in to regenerated and
synthetic.
Basic principle in fiber manufacturing
➢ Conversion of the fiber-forming substance into a fluid by dissolving or
melting.
➢ Extrusion of the fluid through spinnerets.
➢ Solidification of the extruded filaments.

3. 3
3
➢ The technology of man made fiber manufacturing --- SPINNING (Extrusion and solidification)
➢ A spinneret (perforated plate) may have from one to several hundred holes.
Monofilament: when the spinneret has only single hole
Multi-filament: the bunch of filaments from a multi-hole spinneret.
➢ Spinneret hole may be circular or some other shape based on requirement. This enables
production of filaments having different cross-section.
TECHNOLGY OF MAN MADE FIBERS

4. 4
4
SPINNING METHODS
MELT SPINNING
➢ In melt spinning, the fiber-forming substance is melted for extrusion through
the spinneret and then directly solidified by cooling in an air stream.
Key requirements: Ease of melting, melt stability
and optimum melt viscosity
Examples: Nylon, Polyester

5. 5
5
Cont..
SOLUTION SPINNING
➢ In solution spinning the fiber forming polymer is dissolved in a suitable solvent for
extrusion through a spinneret.
➢ The major solution spinning operations are dry spinning and wet spinning.
✓ In dry spinning the polymer solution is extruded into a stream of warm air, which
evaporates the volatile solvent and solidifies the filaments.
✓ In wet spinning the polymer solution is extruded into a bath containing chemicals,
which neutralize the solvent and coagulate (solidify) the filaments.

6. 6
Key requirements: Polymer solubility & solution viscosity
DRY SPINNING WET SPINNING
Example: Viscose rayonExamples: Acetate, Acrylic

7. Flow chart of MMF production:
1. Manufacture of the fibre forming polymer.
2. Spinning ( extrusion and solidification)
3. Stretching/Drawing ( improving strength and crystallinity)
4. Texturing/Crimping ( developing natural fibre properties)
5. Heat setting( made dimensionally stable)
6. Cutting: According to requirements.

8. 8
REGENERATED FIBERS
➢ The raw materials used for the production of regenerated fibers are
natural polymers.
➢ Nature has done the work of preparing something that can be
converted into fiber.
➢ The only involvement of man is converting this material in to a
suitable fiber.
➢ Most widely used regenerated fibers are viscose rayon and acetate.

9. VISCOSE RAYON
➢ The raw material for viscose rayon production is cellulose
obtained from wood pulp.
➢ Viscose rayon fiber is produced by wet spinning technology.
➢ The first step is preparation of a spinnable solution of cellulose
known as viscose.
➢ Next wet spinning is carried out which involves extrusion through
spinnerets & coagulation.
➢ The coagulation bath which consists acids and salts responsible
for neutralization and regeneration of the original cellulose as
continuous filaments.

10. Manufacturing Process of Viscose Rayon
17-20% aqueous sodium
hydroxide (NaOH
at a temperature of 40-50 0c .
H2SO4 = 8-10%
Na2SO4 = 16-24%
ZnSO4 = 1-2%

11. 11
➢ The chemical structure of viscose is comparable to cotton.
➢ The cellulose molecules are much shorter than those of cotton
➢ Their organization in the fiber is also different (low degree of crystalline)
➢ The fiber cross-section is serrated and longitudinally striations are observed
along the length of the fiber.
VISCOSE RAYON: FIBER STRUCTURE AND PROPERTY
DP = 250 -350

12. ❖ The tenacity is lower than cotton and much lower wet strength
❖ The elongation at break is higher than cotton
❖ Viscose wrinkles easily and has high moisture regain than cotton
❖ Low tendency of static charge build up.
PARAMETER CHARACTERISTIC VALUE
Tenacity 2-3
Elongation 10 – 20%
Elastic recovery Moderate
Specific gravity 1.51
Heat Conductivity Moderate
Moisture regain 11- 13%

13. Uses of Viscose Rayon
➢Rayon typically has an elevated luster quality giving it a brilliant
gloss
➢Mainly, Rayon fibres are used in apparel industry such as shirts, blouses, dresses,
Jackets, Lingerie, scarves, suits, ties, hats and socks…,
➢ Some rayon fibers are used for furnishings including bedspreads,
bed sheets, blankets, window covers, upholstery ..,
➢ For industrial purposes such as medical surgery products, non-
woven items, tire cord and some other uses like diapers, towels,
feminine hygiene products..,

15. CELLULOSE ACETATE FIBERS
➢ Acetate rayon is the generic name for cellulose acetate fiber in at least 74%
of the hydroxyl groups of cellulose are acetylated.
➢ The raw material for the production of cellulose acetate fibers is cotton
linters/wood pulp.
➢ The hydroxyl groups of cellulose are replaced by acetate groups.
15
(CH3COO -)

16. ACETATE FIBER MANUFACTURING
➢ Cotton Purification: Cotton linters are first purified to remove impurities.
➢ Pretreatment: Stepping in glacial acetic acid to make reactive for acetylation
➢ Acetylation: Hydroxyls (-OH) in cellulose are replaced by acetyl groups
(CH3COO -)
➢ Treatment with an excess of glacial acetic acid and acetic anhydride
➢ Sulphuric acid dissolved in acetic acid is added to complete acetylation.
➢ All the cellulose is converted into cellulose triacetate
➢ The cellulose triacetate thus formed is known as Primary Acetate
16

17. Manufacturing Process of Cellulose Acetate

18. 18
➢ Preparation of Dope: The blended secondary acetate is mixed three times its
weight of acetone in a closed vessel. Acetone dissolves it slowly.
➢ The solution of cellulose acetate in acetone is the spinning dope. Dope is
filtered, dearated and then run into feed tank.
ACETATE FIBER MANUFACTURING

19. Spinning
➢ The method of spinning used is dry spinning. The dope is extruded through the
spinneret and the acetone solvent is gradually removed by means of warm air.
➢ Post spinning operations as usual and as per requirement.

20. Production Process of CA

21. 21
ACETATE FIBER: MAJOR FEATURES
➢ Presence of bulky side chain groups leading to limited close packing
➢ Presence of hydrophobic groups lower moisture characteristics
➢ Low tenacity [1.4gpd (dry) and 0.9gpd (wet)]
➢ High elongation [30% (dry) and 40% (wet)]
➢ Elastic recovery good at low elongation
➢ Moderate moisture regain [6.5%]
➢ Moderate density [specific gravity 1.32]
➢ Acetate Rayon is more sensitive to heat. It begins to weaken at 93 deg C. At 175
deg C it becomes sticky and melts at 260 deg C. Like nylon and polyester it is
thermoplastic.
➢ Acetate rayon is soluble in acetone.

22. Uses of Acetate fiber
➢ Acetate is used in dresses, blouses, foundation garments,
lingerie, garment linings, some household furnishings
and specialty fabrics.
➢ Triacetate is used in sportswear, tricot fabrics as well as
in certain specialty fabrics.

23. Polyester
➢ These fibres are synthetic textile fibres of high polymers which are
obtained by esterification of dicarboxylic acids, with glycols or by
ester exchange reactions between dicarboxylic acid esters and
glycols.
➢ Thus Terylene is made by polymerising using ester exchange
reaction between dimethyl terephthalate and ethylene glycol.

24. Manufacturing of polyester Filaments
➢Polymerization
➢Drying
➢Melt spinning
➢Drawing the fiber
➢Winding

25. Raw Materials
➢Coal
➢Air
➢Water
➢Petroleum

26. Manufacturing Process of Polyester

27. Production
➢ The polymer is made by heating terephthalic acid with excess of ethylene
glycol ( Both of high priority) in an atmosphere of nitrogen initially at
atmospheric pressure.
➢ A catalyst like hydrochloric acid speeds up the reaction.
➢ The resulting low molecular weight ethylene glycol terephthalate is then heated
at 280 deg C for 30 minutes at atmospheric pressure and then for 10 hours
under vacuum. The excess of ethylene glycol is distilled off.
➢ the ester can polymerise now to form a product of high molecular weight.
➢ The resulting polymer is hard and almost white substance, melting at 256 deg
C and has a molecular weight of 8000-10000.

28. Melt spinning
➢ Polymer chips are melted at 500-518°F (260-270°C) to form a syrup-like
solution.
➢ The solution is put in a metal container called a spinneret and forced
through its tiny holes, which are usually round, but may be pentagonal or
any other shape to produce special fibers.
➢ At the spinning stage, other chemicals may be added to the solution to
make the resulting material flame retardant, antistatic, or easier to dye.

30. Drawing the fiber
➢ When polyester emerges from the spinneret, it is soft and easily elongated up to
five times its original length. This increases the strength, tenacity, and resilience of
the fiber. This time, when the filaments dry, the fibers become solid and strong
instead of brittle.
➢ Drawn fibers may vary greatly in diameter and length, Also, as the fibers are
drawn, they may be textured or twisted to create softer or duller fabrics.
Winding
➢ After the polyester yarn is drawn, it is wound on large bobbins or flat-wound
packages, ready to be woven into material.

31. Polyester Manufacturing process

32. Properties of Polyester
Moisture Regain
At 65% RH and 70 deg F--> 0.4%
Because of low moisture regain, it develops static charge.
Garments of polyester fibres get soiled easily during wear.

33. Cont…
Thermal Properties
Polyester fibres are most thermally stable of all synthetic
fibres. As with all thermoplastic fibres, its tenacity decreases
and elongation increases with rise in temperature. When
ignited, polyester fibre burns with difficulty.
Shrinkage
Polyester shrinks approx 7% when immersed in an
unrestrained state in boiling water. Like other textile fibres,
polyester fibres undergo degradation when exposed to
sunlight.
Its biological resistance is good as it is not a nutrient for
microorganisms.

34. Cont…
Swelling and Dissolving
The fibre swells in 2% solution of benzoic acid, acrylic acid and
phenol.
Alcohols, Ketones, soaps, detergents and dry cleaning solvents
have no chemical action on polyester fibres.
Chemical Resistance
Polyester fibres have a high resistance to organic and mineral
acids. Weak acids do not harm even at boil. Similarly strong acids
including hydrofluoric acids do not attack the fibres appreciably in
the cold.

35. Major Polyester Fiber Uses
➢ Apparel: Every form of clothing
➢ Home Furnishings: Carpets, curtains, draperies, sheets and
pillow cases, wall coverings, and upholstery
➢ Other Uses: hoses, power belting, ropes and nets, thread, tire
cord, auto upholstery, sails, floppy disk liners, and fiberfill for
various products including pillows and furniture .

36. Nylon 6
➢ The polyamide fibers include the nylons, 6 and 6,6, and the aramid
fibers. Both fiber types are formed from polymers of long-chain
polyamides.
➢ The nylons generally are tough, strong, durable fibers useful in a
wide range of textile applications.
➢ Manufacturing Process of Nylon 6

37. Manufacturing Process of Nylon 6
➢ It is made from Caprolactum which is made by a series of
reactions using products obtained from coal tar.
➢ Coal Tar--> Benzene--Chlorine--> Chlorobenzene--> Sodium
Phenate--HCL--> Phenol--H2 (Nickel)-->Cyclohexanol--
Oxidation Air Fe, Zn Catalyst--> Cyclohexanone-->
Cyclohexanone Oxime--H2SO4--> Caprolactum

38. Melt Spinning
➢ Continuous filaments are made by melt spinning.
➢ Dry polymer chips are fed to a melt spinning apparatus, wherein
one section of the chips fall, into a melting region where they are
heated electrically to 250-260 deg C.
➢ The molten polymer flows into a conical section to form a pool,
which feeds a spinning pump and spinnerets.
➢ The pool is kept under an atmosphere of nitrogen to prevent
decomposition by air.

39. Cont…
➢ The molten polymer leaving the pump is filtered before entering the spinnerets
which is a stainless steel disc having a number of holes, the number and
diameter of which determine the type of yarn formed.
➢ Before reaching the machine in which cheese is build up, the filaments are
moistened with water to ensure dimensional stability of the final packages.
➢ The yarn thus formed is not strong enough and has a very high extensibility.
➢ The yarn contains a large number of macro molecules which are un-oriented
and these must be oriented so as to lie parallel to the length of the fibre to
develop full strength.
➢ This is done by stretching the yarn to 3-4 times its original length.

40. Properties of Nylon 6
Mechanical Properties
➢ Density: 1.14 g/cc
➢ Tenacity: Dry= 4.2-5.8 gpd, Wet=4.0-5.3 gpd
➢ Elongation at Break--> Dry = 24-40, Wet=28-43
➢ Elastic Recovery at 4% extension= 100%
➢ Moisture Regain= 4%
➢ Because of low MR, wet nylon dries quickly.
➢ Melting Point= 215 deg C ( Nylon 66-250 deg C)
➢ It is weakened by prolonged exposure to sunlight.

41. Cont…
Chemical Properties
➢ It is resistant to most organic acids such as benzene,
chloroform, acetone, esters ethers etc.
➢ It dissolves in phenol, cresol and strong mineral acids.
➢ good resistant towards alkalies.
➢ Resistant to inorganic acids
➢ These fibres are cylinderical in shape, with smooth surfaces and
without having any markings. The fibres are unifrom in diameter
and appear round in cross section.
➢

42. Uses of Nylon
➢ Articles made from nylon, such as socks, ropes, tents, toothbrushes, car seat
belts, sleeping bags, curtains and umbrellas etc.
➢ It is used for making fabrics in textile industry.
➢ Nylon is a high strength fibre. It is used for making fishing nets, ropes,
parachutes and tire cords.

43. Nylon 6,6
➢ The nylons generally are tough, strong, durable fibers useful in
a wide range of textile applications.
➢ Manufacturing Process of Nylon 6,6

45. Cont…
➢ Nylon 6,6 is made from Hexamethylene diamine and adipic acid
as shown in the figure below.

46. Spinning of Nylon 6,6

47. Cont…
➢ The chips of nylon polymer are fed through a hopper A, into a
spinning vessel B, on an electrically heated grid ( perforated
plate) C. The perforations are so small that the chips do not pass
through, but when melted, the liquid can pass.
➢ The molten nylon collects as a pool D, at the bottom of the
vessel. This liquid should not come into contact with oxygen or
air and hence nitrogen is introduced into the vessel.
➢ The molten polymer is kept at a temperature of about 288 deg C
and sucked by a pump F, into a spinneret E.

48. ➢ The molten polymer solidifies as soon as it emerges out of the
spinnerette.
➢ The filament thus formed pass through a cooling zone, in
which cold air G circulates directed towards the filaments.
➢ The filaments are then passed through a steam chamber H, to
wet them before winding on the bobbin L.

49. Cont…
Drawing
➢ Nylon filaments as obtained are not very strong.
➢ They have to be drawn 4-7 times their original length.
➢ This is done by cold drawing. The yarn in pulled off from
bobbin L through guides M and N, between a pair of rollers .
➢ The speed of rotation of these rollers determines the initial
speed. The yarn then goes over a deflector P, and two to
three times around roller Q, running at five times the speed
than that of O.
➢ The yarn subsequently courses through another guide R,
and wound on another bobbin which rotates at very high
speed, to impart twist in the yarn before being wound.

50. Properties of Nylon 6,6
Strength
✓ The most outstanding property of nylon is its strength and elasticity.
✓ The tenacity varies from 4.3-8.8 g/d while corresponding elongation at break varies from
18-45%.
✓ The wet strength of nylon is 80-90% of its dry strength and the elongation at break
increases by 5-30% on wetting.
✓ Density: 1.14 g/cc
Elastic Recovery
✓ When nylon yarn is stretched 1,2 and 4% with a load of 0.25 gpd for 30 seconds and then
released the recovery after 60 seconds is 38, 63 and 73% respectively.
Moisture Regain
✓ Nylon has a moisture regain of about 4% at 65% RH and 70 deg F.
Action of Light
✓ Like other fibres, nylon undergoes degradation and weakens when exposed to lights.
Appearance
✓ Nylon is dull and semi opaque before cold drawing, but on orientation its lustre is greatly
increased. Delustering is done by adding TiO2 in the polymerization mixture.

51. Chemical Properties
• Nylon is extremely stable chemically. For example dry cleaning
solvents, alcohols, aldehydes, ketones, ethers, hydrocarbons,
chlorinated hydrocarbons, soaps and synthetic detergents and water
including sea water do not affect Nylon.
• Also it has got a remarkable stability towards alkali.

52. PAN (Acrylic)
➢ The acrylic fibers include acrylic, modacrylic, and other vinyl
fibers containing cyanide groups as side chains.
➢ Among the major acrylic fibers, acrylonitrile is the comonomer
containing a cyanide group.
➢ Acrylic fibers are formed from copolymers containing greater
than 85% acrylonitrile monomer units, whereas modacrylic fibers
contain 35%–85% acrylonitrile units.

53. Cont…
➢ Polyacrylonitrile (PAN):- Polyacrylonitrile (PAN) is a
synthetic, semicrystalline organic polymer resin, with the
linear formula (C3H3N)n.
➢ It is a versatile polymer used to produce large variety of
products including ultra filtration membranes, hollow
fibers for reverse osmosis, fibers for textiles, oxidized
flame retardant fibers like PANOX and carbon fiber. PAN
fibers are the chemical precursor of high-quality carbon
fiber.

54. PAN (Acrylic)- Manufacturing Process
• Acrylonitrile is the main raw material for the manufacture of
acrylic fibres. It is made by different methods. In one
commercial method, hydrogen cyanide is treated with
acetylene:
• acetylene + Hydrogen cyanide --> Acrylonitrile

55. 2nd Method
➢ Ethylene--Air Oxidation--> Ethylene oxide + HCN--> Ethylene
cyanahydrin--Dehydration at 300 deg C (catalyst)-->
Acrylonitrile
➢ In a continuous polymerisation process, 95% acrylonitrile and
6% methyl acrylate (400 parts) 0.25% aqueous solution of
K2S2O8(600 parts), 0.50 % Na2S2O5 solution ( 600 Parts) and
2N sulphuric acid (2.5 Parts) are fed into the reaction vessel at
52 deg C under nitrogen atmosphere giving a slurry with 67%
polymer.
➢ The slurry is continuously withdrawn, filtered and washed till it
is free from salts and dried.

56. Properties of Acrylic Fibres
➢ Acrylic has a warm and dry hand like wool. Its density is 1.17
g/cc as compared to 1.32 g/cc of wool. It is about 30% bulkier
than wool. It has about 20% greater insulating power than wool.
➢ Acrylic has a moisture regain of 1.5-2% at 65% RH and 70 deg
F.
➢ It has a tenacity of 5 gpd in dry state and 4-8 gpd in wet state.
➢ Breaking elongation is 15% ( both states)
➢ It has a elastic recovery of 85% after 4% extension when the
load is released immediately.

57. Cont…
➢ It has a good thermal stability. When exposed to temperatures
above 175 deg C for prolonged periods some discolouration
takes place.
➢ Acrylic shrinks by about 1.5% when treated with boiling water
for 30 min.
➢ It has a good resistance to mineral acids. The resistance to
weak alkalis is fairly good, while hot strong alkalis rapidly
attack acrylic.
➢ Moths, Mildew and insects do not attack Acrylic.
➢ It has an outstanding stability towards commonly bleaching
agents.

58. Uses of Acrylic Fiber
➢Socks, hats, gloves, scarves,
knit garments, sweaters, Coats
Blankets and shoe soles
➢Home furnishing fabrics:
Carpets and rugs.

59. Thank You