This document discusses the production of polyester fiber through various fiber production processes. It begins by defining polyester as a long-chain polymer composed of at least 85% ester units formed from the reaction of alcohols and acids. The key raw materials used are terephthalic acid, ethylene glycol, and dimethyl terephthalate. Polyester fiber can be produced through two main routes - the dimethyl terephthalate route and the terephthalic acid route. The document provides detailed information on the chemical reactions, catalysts, side reactions, degradation processes, and thermal stabilizers used in each production route.

1. PRODUCTION OF POLYESTER
FIBRE
&
FIBRE PRODUCTION PROCESSES
SUBMITTED TO:
Dr. Supriyo Chakraborty Sir
SUBMITTED BY: Nirbhay Beri
Branch : Textile Chemistry
Roll no : 1804460029

2. POLYESTER
• Polyester is a term used for “long-chain polymers chemically composed of at least
85% by weight of an ester which is organic salt formed from the reaction between an
alcohol and an acid. ” Polyester also refers to the various polymers in which the
backbones are formed by the “esterification condensation of polyfunctional alcohols
and acids”. Polyester is a man-made, synthetic polymer, filament or staple fibre.
Polyester textile filament or staple fibre is composed of polyethylene terephthalate
polymers.
• Polyesters are a medium weight fiber with a density of 1.39 g/cm 3. As it is heavier
than nylon, polyester textile materials are manufactured as 'thin' fabrics, since thick
polyester fabrics are too heavy.
2

3. MACRO STRUCTURE OF POLYESTER
• Polyester is fine, regular and translucent filament or staple fiber. Both filament and staple fibers
are manufactured in crimped or textured configuration. Crimping increases the inter-fiber friction,
results in better fiber cohesion during and after spinning of its yarn and improved texture.
• The length of the polyester filaments depends upon the size of the yarn package onto which it is
wound. The length of the staple fiber is comparable to cotton or wool.
• The diameter polyester filaments or staple fibers range from 12 μm to 25 μm. Diameter depends
upon end-use requirements. The fiber length to breadth ratio usually exceeds 2000: 1 and ensures
that even the shorter polyester staple fibers can be satisfactorily spun into yarn.
• The color of fiber is slightly off white. Most of the incident light upon polyester is reflected with
considerable intensity from filaments or staple fiber’s smooth and regular surface. This results in
harsh and bright luster. Like other man-made fibers it lacks a discernible fiber micro structure and
impurities, thus permitting some light to pass through the fiber, which makes them translucent
3

4. MICROSCOPIC APPEARANCE OF POLYESTER
• Polyester filaments have no identifiable microscopic appearance. The longitudinal
appearance of the fiber is very regular and featureless because of the near circular
cross-section. The magnified appearance of polyester is similar to a glass rod.
4

5. TYPES OF POLYESTER
5

6. RAW MATERIAL FOR
POLYESTER PRODUCTION
Terephthalic Acid
(TPA)
Monoethylene Glycol (MEG)
Dimethyl terephthalate (DMT)
6

7. TEREPHTHALIC ACID
Terephthalic acid is an organic compound with formula C6H4(CO2H)2. This white solid
is usually obtained by the catalytic oxidation of p-xylene in air, in the presence
of acetic acid (HAc) as solvent. Once the synthesis is done, the solvent is to be recycled
and reused back to the chemical reaction media.
7

8. ETHYLENE GLYCOL
• Ethylene glycol (IUPAC name: ethane-1,2-diol) is
an organic compound with the formula (CH2OH)2. It is an
odorless, colorless, sweet-tasting, viscous liquid.
• Ethylene glycol is produced from ethylene (ethene), via the
intermediate ethylene oxide. Ethylene oxide reacts
with water to produce ethylene glycol .
• Ethylene glycol is produced from carbon monoxide in
countries with large coal reserves and less stringent
environmental regulations. The oxidative carbonylation of
methanol to dimethyl oxalate provides a promising
approach to the production of C1-based ethylene
glycol. Dimethyl oxalate can be converted into ethylene
glycol in high yields (94.7%) by hydrogenation with a
copper catalyst
8

9. DIMETHYL TEREPHYTHALATE
• Dimethyl terephthalate (DMT) is an organic
compound with the formula C6H4(COOCH3)2.
It is the diester formed from terephthalic
acid and methanol. It is a white solid that
melts to give a distillable colorless liquid.
• Dimethyl terephthalate (DMT) has been
produced in a number of ways. Conventionally,
and still of commercial value, is the direct
esterification of terephthalic acid.
Alternatively, it can be prepared by alternating
oxidation and methyl-esterification steps
from p-xylene via methyl p-toluate
9

10. ALIPHATIC POLYESTER
• Aliphatic polyesters can be considered as representatives of synthetic biodegradable
polymers.
• Synthesis of aliphatic polyesters by polycondensation of diols and dicarboxylic acids was
reported as early as 1930.
• However, the low melting points, low hydrolytic stability, and low molecular weights of
the polymers initially obtained severely limited their application. At the same time, their
high hydrolytic instability resulted in a multitude of applications for this class of
polymers in the biomedical field.
• This new avenue revitalized interest in these polymers, and novel synthetic methods, as
well as catalytic systems, were developed to obtain high-molecular-weight polymers with
narrow molecular weight distributions
10

11. • The commonly used monomers for the synthesis
of aliphatic polyesters for biomedical applications
are lactide, glycolide, and caprolactone.
• Aliphatic polyesters are the most readily
biodegradable systematic polymers. It was found
that polyesters derived from diacids of medium
size monomers (C6–C12) are more readily
degraded by fungi as well as elastase, than those
derived from longer and shorter monomers.
• A balance of hydrophobicity (monopolarity)
and hydrophilicity (polarity) seems to be an
optimal condition for biodegradation. In order for
a synthetic polymer to be degradable by enzyme
catalysts, the polymer chain must be able to fit
into the enzyme active site. This is the main
reason that flexible aliphatic polyesters are
degradable and the rigid aromatic polyesters are
not. 11
Cont

12. POLYESTER FORMING ROUTES..
Poly(ethylene terephthalate) is a step growth (condensation) polymer and is produced
industrially by one of the following two routes:
• 1. DMT route: raw materials are dimethyl terephthalate (DMT) and
monoethylene glycol (MEG);
• 2.PTA route: raw materials are terephthalic acid (TPA) and monoethylene glycol
(MEG).
12

13. POLYETHYLENE TEREPHTHALATE (PET)
FROM DMT
PET from DMT is made by transesterification route by reaction of dimethyl terephthalate with ethylene
glycol followed by poly-condensation. Polyester through trans esterification route was more common
earlier due to non-availability of purified terephthalic acid. During transesterification, methanol obtained
as by product.
13

14. In the DMT route, the first step is transesterification followed by
polycondensation (PC). A flow diagram of PET manufactured by this
route .The following four aspects relating to this process will be:
(1) Catalysts used,
(2) Side reactions,
(3) Degradation
(4) Thermal stabilizers.
14

15. 1.CATALYSIS
Catalysts used Transesterification involving DMT and MEG is a slow process and requires a catalyst
to augment the process. The catalyst can be (1) a metal, (2) a metal oxide, or (3) a metal salt. Usually
a metal oxide or a metal salt of a weak or volatile acid is used. Acetates of various metals are most
commonly employed in industry; the catalytic reactivity of these acetates follows the order
Zn > Pb > Mn > Co > Mg > Ca > Sn > Na > Sb
To achieve a balance between these two opposing effects, usually a combination of a high activity
catalyst with a low activity one is used in the industry. A catalyst amount of 0.02-2% is common. It
must be remembered that all catalysts used in the TE step enhance PET degradation in the PC stage.
For this reason it has become customary to use catalyst deactivators in the PC stage. Antimony-based
catalysts are unique as they do not catalyze the EI step but become active in the PC step. The most
commonly used antimony-based catalysts include antimony trioxide and antimony triacetate.
15

16. 2.SIDE REACTIONS IN DMT ROUTE
Several side reactions may occur during the EI step. They also occur in the DE step in the PTA
route….
16

17. • The catalyst system chosen for polymerization affects the molecular structure of PET
and has a considerable influence on the crystallization behavior of PET. Diethylene
glycol is formed at each stage of PET synthesis
• DEC increases the dye affinity of PET fibres. It is difficult to maintain a constant
level of DEC and hence with a varying amount of DEC, dye affinity will also change.
Presence of DEC in the product makes it soft and the pills break away more easily
with an increasing amount of DEC
Reaction between two ethylene glycol
molecules:
17

18. 3.DEGRADATION
• The PET melt is thermally unstable and undergoes degradation at high polymerization temperatures,
particularly above 150°C, especially during the PC stage.
• Once degradation starts, the degraded products can undergo further reactions and it is not possible to
predict the course of such reactions. The degradation may initiate at chain ends , or it may originate by
scission of a PET chain . Frequently, discoloration of PET occurs during degradation and it has been
postulated that acetaldehyde formation has a role to play in it
Some degradation reactions are:
18

19. CHAIN
SCISSION….
The final product is affected by
the degradation in the
following
ways:
• • The molecular weight is
lowered and becomes
unpredictable;
• There is yellow coloration;
• There is an increase in
carboxyl end groups with a
resultant decrease in the
thermal stability of PET.
19

20. 4.THERMAL STABILIZER
To minimize thermal degradation of the PET melt, thermal stabilizers are added. Generally,
compounds of phosphorus or phosphoric acid are added prior to the PC stage. They deactivate
the catalysts used during the EI step .Commercially, triphenyl phosphite (TPP),trimethyl
phosphate (TMP), tetraethyl ammonium hydroxide (TEAOH) and trisnonyl phenyl phosphite
(TNPP) are commonly used.
Some of the antimony-based catalysts used during the PC stage are reduced to metallic
antimony (Sb) by such stabilizers. This occurs more for p3+ than pS+ stabilizers. Formation
of antimony metal imparts a grey-green tinge to PET. It is claimed that TNPP does not affect
antimony triacetate.
To produce a completely white PET, the use of germanium oxide (Ge02) as a catalyst is
recommended in the PC stage instead of antimony trioxide.
20

21. Flow diagram for the manufacture of
polyester fiber by the DMT route
21

22. POLYETHYLENE TEREPHTHALATE (PET)
FROM PTA
PET from purified terephthalic acid (PTA)is made by esterification route by reaction of
purified terephthalic acid (PTA) with ethylene glycol followed by polycondensation.
22

23. Flow diagram for the manufacture of
polyester fiber by the TPA route…….
23

24. 1. Cost of TP A is usually less than DMT.
2. During DGT formation, the by-product methanol is not formed.
3. The DE step is self-catalysed
4. Product quality is superior.
5. The reaction product in the DE step has a higher molecular weight than that
obtained in the EI step.
24

25. BATCH AND CONTINUOUS PROCESSES
• 1. Batch process : The polymer produced by the batch process shows considerable
fluctuation in quality from batch to batch and the PET chips are therefore blended before
spinning. To eliminate chip agglomeration and melt hydrolytic degradation, chips are
crystallized and dried before being remelted in screw melter and then fed to spinning
machines.
• 2. Semi continuous process: In this process also the chips are blended before melt-
spinning.
• 3. Continuous process:In this process, the polymer from the last polycondensation vessel is
pumped directly to spinning machines for melt-spinning into fibres and therefore eliminates
the PET chips manufacture, handling, drying and remelting steps.
25

26. Batch Polymerization And Screw
Melter Spinning (Batch Process)
continuous polymerization and screw
melter spinning (semi continuous
process)
26

27. Continuous Polymerization Direct
Spinning (Continuous Process);
Transfer Line Injection On-line Compounding
27

28. SOLID STATE POLYMERISATION
• Solid State Polymerization (SSP) is a
process in which the polymer chain lengths
are increased by heat in the absence of
oxygen and water, by means of either
vacuum or purging with an inert gas to
drive off the by-products of reactions. The
reaction is driven by temperature, pressure,
and the diffusion of by-products from the
interior of the pellet to the surface. SSP is
an important step frequently used after
melt-polymerization for the purpose of
enhancing the mechanical and rheological
properties of polymers before injection blow
molding or extruding. The SSP technique is
widely applied in industrial manufacture of
bottle-grade PET, films, and superior
industrial fibers.
28

29. Continuous polymerization Solid phase polymerizationBatch melt polymerization
Blend
PRINCIPAL STAGES IN POLYESTER FIBRE PRODUCTION
29

30. BLENDING, DRYING ,MELTING
Batch-wise production results in difference
in molecular weight, molecular weight
distribution, melting point, color and DEG
content, etc. The differences may be from
batch to batch or even within the same
batch. Hence blending is practiced to
obtain uniform, homogeneous product and
for this, large-scale blending facilities are
required
To prevent hydrolysis of ester groups, the
blended PET chips are dried before being
subjected to melting. Drying is usually
carried out in large driers at around 170°C
by passing dry hot air through a bed of
polymer granules. The moisture content in
the dried polymer should be no more
than 0.005% by weight.
Blending…. DRYING……
30

31. • To avoid fusion of polymer chips during drying,
the granules are pre crystallized at 100-120°C in
batch-wise dryers. Since dried polymer picks up
water very rapidly, it is fed directly to the hopper
of thee extruder under dry nitrogen without
further exposure to air.
• The melting is generally achieved in a screw
extruder. The extruders are single or twin screw
vented types, which feed manifolds leading to
spinning heads that contain individual gear
pumps.
MELTING IN BATCH PROCESSING OF
POLYESTER
31

32. Production of polyester
Filament Yarn…
32

33. PET MELT-SPINNING PROCESSES..
• PET melt-spinning processes can be considered to fall broadly into two distinct classes:
(1) In which relatively low wind-up speeds are used to produce a spun yarn possessing little or no
orientation.
(2) In which relatively high wind-up speeds are used to produce a partly oriented spun yarn
• Fiber products and processes and considers the products in four categories of spinning speeds, namely:
1. low spinning speed in the range 500-1500 mmin-1: the product is called low-oriented yarn (LOY);
2. medium speed in the range 1500-4000 mmin-1: the product is called partially oriented yarn (POY);
3. high speed in the range 4000-6000 mmin-1: the product is called highly oriented yarn (HOY);
4. very high speed in the range above 6000 mmin-1: the product is called fully oriented yarn (FOY).
33

34. LOY SPINNING PROCESS
• The as-spun PET fiber obtained at spinning speeds in the 500-1500 m/min range is virtually
amorphous, has very little strength, is highly deformable and typically must be drawn to four to
five times its original length to obtain a useful fiber.
• The practical approach is to spin a fairly high molecular weight PET at very low speeds and
sometimes with a retarded quench to obtain minimum spin orientation and then subject it to a
draw ratio in the 5-7 range.
• The drawn filament can develop high birefringence of 0.21 or even more.
• LOY products are also used for textile applications and the production of tow.
• Here only adequate strength is usually desired and other factors such as dimensional stability and
dyeability are important. These requirements are met by giving the fibres a slightly higher spin
orientation and a draw ratio of up to 4.
34

35. POY SPINNING PROCESS
POY became a commercial reality in the early 1970s mainly because of the availability of commercial
winders with higher speed ranges (3000 m/min or higher) around that time and also because of the
introduction of simultaneous draw-texturing in 1970.
• The tensions generated in the yarn are now higher and though the as spun fibre is almost completely
amorphous, the level of orientation developed gives it substantially higher strength and lower
extensibility than LOY.
• POY overcomes both the shortcomings of LOY, namely
1.The difficulty in stringing-up on the texturing machine and
2. The shelf-life problem of he low speed spun yarn. Because of its increased orientation.
• The crystallizability of POY is many orders of magnitude higher than that of LOY.
• The drawn filament can develop high birefringence of 0.038.
• In general, POY spinning is currently carried out at relatively high speed (3000 m/min) without godets.
This offers advantages in the areas of capital costs and ease Of string-up, but has the major disadvantage
of lack of wind-up tension control. 35

36. HOY & FOY SPINNING PROCESSES
• The high thread line tension in this speed range
arises from air drag (associated with the large
volume of air pumped downwards by the
filaments) and inertial (associated with the
acceleration of the threadline to the final
spinning velocity) contributions.
• It causes very rapid filament attenuation and
extensive molecular orientation. The thread line
tension is the key process parameter controlling
thread line crystallization kinetics.
• A considerable amount of work on ultra high
speed spinning of PET yarn at speeds in the
range 6000-8000 m/min has shown that neck
like deformation occurs at high temperatures
and the fiber has a strong skin-core structure.
• The extrusion temperatures for normal
molecular weight are in the range 280-2900C.
However, products of low molecular weight may
be spun at temperatures down to 2650C and
those of very high molecular weight at 3000C or
above.
HOY SPINNING PROCESS FOY SPINNING PROCESS
36

37. DRAWING OF FILAMENT YARN
• The spun yarn of low orientation is subjected to a stretching or drawing process to
convert it into commercially useful yarn of high orientation.
• Total draw ratios lie between 3 and 6. The higher draw ratios are for high tenacity
yarns and often involve a two-stage drawing process, wherein the second stage is
carried out at a somewhat higher temperature than the first (which is usually
carried out at 90-100 0C) and applies a draw of up to 1.5.
• The process of drawing introduces some crystallinity but insufficient to stabilize the
yarn against thermal shrinkage. Further setting during the draw process itself
through passage over a hot plate at 140-220°C or by using a heated draw roller at a
similar temperature is usual in filament yarn production.
37

38. TEXTURING OF POLYESTER FILAMENT YARN
• Simultaneous draw-texturing of POY using friction-twisting devices
based on aggregates of intermeshing discs and operating at speeds up
to 1000 m/min is often adopted to produce false-twist textured yams.
• Other texturing methods can also be used to produce textured yams
from POY supply.
38

39. PHYSICAL PROPERTIES OF POLESTER
o Tenacity
 Polyester filaments and staple fibers
are very strong because of their
extremely crystalline polymer system.
 High tenacity ensures above-average
wear qualities. This high crystallinity
ensures the formation of the very
effective Van der Waals forces as well as
the weak hydrogen bonds, resulting in
the very good tenacity.
 The tenacity of polyester filaments or
staple fibers remains unaltered when
wet due to the hydrophobic and
extremely crystalline polyester polymer
system which restricts the entry of
water molecules.
o Elastic-plastic nature
• Extremely crystalline polymer
system results in stiff and hard
handle of polyester filaments or
staple fibers and their resulting
textile material.
• The extreme crystallinity of the
polymer system prevents the
polyester filament or staple fiber
from bending which results in
wrinkle or crease resistance
• Polyester filaments are about as
plastic as they are elastic. Plasticity
of polyester filaments or staple
fibers gives rise to the distortion on
repeated stretching and straining of
textile material. This is due to the
Van der Waals forces which hold
the polyester polymer system
together
o Hygroscopic nature
• Non polarity and the
extremely crystalline
structure of polyester
polymers resist the entry of
water molecules into the
polymer system, makes
polyester filaments and
staple fibers as hydrophobic
in nature.
• Polyester polymer system is
oleophilic in nature as
hydrophobic polyester
polymer system attracts
fats, greases and oils.
39

40. THERMAL PROPERTIES
•
Polyester shows the poor heat conductivity and low heat resistance. Polyester is not
greatly affected by (dry) temperatures of up to 180°C, except on prolonged exposure.
• The melting point of polyester is 250°C. Heat causes the polyester polymers to become
excited and this result in a breakdown of inter-polymer bonding.
• The handle is restored as soon as the polyester is cooled because most of the broken
hydrogen bonds are reformed. The application of excessive heat causes the polyester
polymers to become so excited that most of the polyester textile material melts.
• The application of more heat will result in burning. If heat is applied under controlled
conditions, the polyester material can be heat set by breaking the inter polymer hydrogen
bonds. During heat setting of polyester, the objective is to break those hydrogen bonds
which are under strain to enable the material to assume the desired configuration
40

41. CHEMICAL PROPERTIES
Effect of acids
The ester groups of the polyester polymers are resistant to acid hydrolysis. This resistance is due to the
extreme crystallinity of the polyester polymer system which prevents the entry of any acid and water
molecules into the filament of staple fiber.
Effect of alkalis
During laundering alkalies, may hydrolyse the polyester polymers at their ester groups. But extreme
crystallinity of the polyester polymer restricts the hydrolysis to the surface of the polyester filament or
staple fiber. As the hydrolysis of polyesters is restricted to the surface, polyester textile materials retain
their whiteness during laundering. Regular laundering and continued hydrolysis of the polyester textile
material causes the loss of a surface film of polyester polymers which will result in finer and silkier
textile material.
Effect of bleaches
Normally polyester textile materials do not need to be bleached as polyester retains its whiteness during
normal domestic laundering.
Effect of bleaches
Normally polyester textile materials do not need to be bleached as polyester retains its whiteness during
normal domestic laundering.
41

42. APPLICATIONS OF POLYESTER
• In the apparel area, polyester (PET) has gained considerably in significant segments of the market at the
expense of polyamides, mainly because of the better easy-care characteristics and wrinkle resistance of
polyester.
• PET fibres make one of the strongest and longest-lasting sutures. In surgical sutures, properties of
particular importance are tensile strength, strength retention in the body's environment, and knot
strength. For surgical implants, e.g. replacement for diseased or malfunctioning blood vessels, knitted or
woven PET porous tube with a smooth, lightly napped surface is the material of choice.
• Polyester has more flat-spotting resistance than nylon and is an important reinforcing fibre for car tyres.
Due to their high modulus and strength, polyester fibres are useful for conveyor belt and rubber hose
reinforcement.
• In soil engineering (geotextiles), polyesters find considerable use as Fibrous structures, mainly non-
woven, for drainage and reinforcement. They are mainly used for earth stabilization in the construction of
roads, embankments and dams.
42

43. MELT-SPINNING VARIABLES OR FACTORS
• There are many state variables involved in melt-spinning which determine the
course of fibre formation divided these variables into three groups:
1. Independent or primary variables, which uniquely determine the course of the
spinning process and the resulting fibre structure and properties.
2. Secondary variables, which are related to primary variables through simple
geometrical relationships and are useful in defining spinning conditions.
3. Resulting variables, which are determined by the independent variables through
the fundamental laws of spinning kinetics.
43

44. These groups can be subdivided as follows.
1. Independent (primary) variables:
(a) Polymer material; (b) Extrusion temperature ; (c) Spinneret channel dimensions ;
(d) Number of filaments in the spinning line ; (e) Mass output rate ; (f) Spinning
path length (L); (g) Take-up velocity ; (h) Cooling conditions (cooling medium, its
temperature and flow rate).
2. Secondary variables:
(a) Average extrusion velocity; (b) Equivalent diameter of a single filament ;(c) Denier of the
filament ;(d) Deformation ratio or melt-draw ratio,
3. Resulting variables:
(a) Tensile force at take-up device;(b) Tensile stress at take-up device, (c) Temperature
of filament a(d) Filament structure (orientation, crystallinity, morphology).
44

45. IDEA ABOUT FIBRE PRODUCTION
PROCESSES
45

46. FIBRE FORMATION
• The conversion of fibre from polymers involves the following principles:
1. Reduction of the polymeric material to a liquid state by melting or by dissolving in a
solvent or in some solubilizing agent.
2. Extrusion of the liquid under pressure through find holes or orifices in a spinneret.
3. Rapid and continuous solidification of the extruded liquid .
• The main methods used for fibre formation i.e. spinning are determined by the
physical and chemical properties of the polymer, owing to this spinning can be of two
types melt spinning and solution spinning .
• Due to differences in solidification process solution spinning can be further sub
divided into two types of spinning i.e, dry spinning and wet spinning
46

47. EXTRUDER
• In the past, the granules were melted on grids consisting of a large heating area in the form of ribs
and coils heated from inside.
• Because screw meters or extruders offer the advantages of much higher melting rate, large
capacity, short residence time, pressure build-up, greater homogenization and delivery of a
metered quantity of the melt,
• The extruders consist essentially of a cylindrical barrel within which rotates one or more close-
fitting screws .
• Screws with diameter of 45-300 mm. The barrel is heated along its length by oil or electricity. The
chips are fed to one end of the screw from a feed hopper and are then forced forward through the
barrel by the rotating screw.
• The rotation is achieved at the base of the machine. As the polymer moves forward, it is softened
partly by conducted heat from the barrel walls and partly by frictional heat developed as a result
of mechanical shearing of the polymer by the action of the screw. When it reaches the end of the
screw, the molten and homogenized melt is guided through a changeable filter pack into a gear
pump which meters a desired throughput into the spinneret through another filter assembly.
47

48. Single screw extruders can be considered as
operating with the following distinct regions as one
travels along the length of the screw starting from
the hopper:
1.The feed section or the solids transport zone:
this section lies just beneath the hopper.
2. The compression and melting zone: the solid
polymer chips undergo compression in this zone
because of reduced volume of the screw flights. The
chips start melting at the point where the first liquid
film forms at the barrel wall, which is heated, and
melting
3.The metering zone: in this zone the pressure builds
up and the melt is transported and homogenized.
4.The mixing zone: the feedstock at this stage may
not be entirely homogeneous and the close-clearance
mixing section is incorporated to promote intensive
mixing.
48

49. DRAWING
The spinning processes described above produce some orientation of the long polymers that form spun
filaments. Orientation is completed by stretching, or drawing, the filament, a process that pulls the long
polymer chains into alignment along the longitudinal axis of the fibre and causes them to pack closely together
and develop cohesion
• During the drawing operation the polymer chains slide over one another as they are pulled into alignment
along the longitudinal axis of the fibers .
• As drawing continues, more and more of the molecules are brought to a state where they can pack alongside
one another into crystallites. In these regions the molecules are able to hold tightly together as a result of
intermolecular forces and resist further movement with respect to one another.
• The degree of alignment of fibre molecules affects the properties of a fibre in several ways. The more closely
the molecules pack together, the greater is the ultimate strength, or breaking strength, of the fibre.
• Fibres can be drawn either as an integral part of the spinning operation or in a separate step .
• Fibres such as nylon and polypropylene can be drawn without applying external heat (or at a temperature no
greater than about 70 °C [160 °F])-a process referred to as cold drawing.
49

50. TEXTURING
• Texturing is the formation of
crimp, loops, coils, or wrinkles in
filaments. Such changes in the
physical form of a fibre affect the
behaviour and hand of fabrics
made from them. Hand, or handle,
is a general term for the
characteristics perceived by the
sense of touch when a fabric is
held in the hand, such as
drapability, softness, elasticity,
coolness or warmth, stiffness,
roughness, and resilience 50

51. CRIMPING
• In order for staple fibres to be spun into yarn, they must have a waviness, or crimp,
similar to that of wool.
• This crimp may be introduced mechanically by passing the filament between gear
like rolls
• It can also be produced chemically by controlling the coagulation of a filament in
order to create a fibre having an asymmetrical cross section that is, with one side
thick skinned and almost smooth and the other side thin-skinned and almost
serrated
• When wet, such fibres swell to a greater extent on the thin-skinned side than on the
thick-skinned side, causing a tendency to curl
51

52. THE SPINNING MANIFOLD
• The design and heating conditions of the spinning manifold have a significant effect on the
filament quality and therefore need careful consideration.
• In a typical spinning unit, the polymer fluid may be conveyed from the last polycondensation
vessel .The polymer fluid is delivered to a number of spinnerets, each equipped with a
spinning pump.
• There are two important requirements: first, all melt paths before reaching the Spinneret
orifice must be of exactly the same length to ensure equality of pressure, which in turn
ensures that the same quantity of material reaches each orifice; and second, the melt streams
and the spinneret must have identical temperature profiles. To ensure melt homogeneity and
a uniform temperature profile, static mixers are installed in front of the metering pumps
52

53. THE SPIN PACK AND THE SPINNERET
• The polymer melt is transported under pressure to spinning heads where an exact metering
pump.
• The spinning head has a polymer inlet through which the molten polymer enters into the pump
block and a metered quantity of the melt is then led through it into the spin pack
• The gear pump consists of three surface-ground steel plates : a base, a central and a cover plate,
which are firmly screwed to one another. The central plate has two gear wheel the shafts of
which lie in the base and cover plate. Pumps are made of high grade steel containing
molybdenum and vanadium.
• Spinning of fine filaments normally requires spinning pumps of 1-4 cm capacity per revolution
and 10-35 rev/min.
• The spinning of coarse filaments or staple fibre requires pumps with a considerably greater
capacity of about 20 cm3 per revolution and more.
53

54. THE COOLING SYSTEM
• For the cooling, for instance: a distance of 5-6m at take-up speeds of 600-800 m/min it was
necessary, corresponding to a cooling time of approximately 0.7 s. The boundary layer of air
formed by air friction on the filament caused poor heat convection and a certain instability in the
thread path.
• A 1939 Du Pont patent claimed that the boundary layer could be made as small as possible by
providing a cross-flow of air, thus reducing the thread cooling path to 1.5 m, corresponding to a
cooling time of about 0.5 s.
• Many important developments in later years have reduced the cooling time to 0.05 s for fine
yarns.
• The following types of quenching systems are in use
• 1. cross-flow quench;
• 2. in-flow quench;
• 3. out-flow quench.
54

55. Quench systems for synthetic filament yarns:
(a) cross-flow quench, round and rectangular spinnerets;
(b) in-flow quench; (c) outflow quench
(a)
(b) (c)
A spinning head 55

56. REFERENCES
• NPTEL (may 10,2020),”Textile fibres/ Synthetic fibres-Polyester” https://nptel.ac.in/courses/116102026/
• ELSE SILVER (may 10,2020),” Continuous Filament Yarn –An Overview”,
https://www.sciencedirect.com/topics/engineering/continuous-filament-yarn
• Multibrief ,(may 9,2020)” Mechanism in Post condensation polymerization in solid
state.http://www.multibriefs.com/briefs/exclusive/post_condensation_polymerization.html#.XrhqU2gzbV
• ELSE SILVER (may 10,2020),”Spinning Process-An Overview” .
https://www.sciencedirect.com/topics/engineering/spinning-process
• Springer,(may 9 ,2020).”Development of an efficient route for combined recycling of PET and cotton from
mixed fabrics | Textiles and Clothing Sustainability | Full
Text”https://textclothsustain.springeropen.com/articles/10.1186/s40689-017-0026-9
• Kothari V.K ,Gupta V.B ,(2012)”Manufactured Fibre Technology", Springer Publication.
• COOK J. GORDON ,(2009),” Handbook of TEXTILE FIBRES”, Woodhead Publishing Limited.
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