Polyester fibers are long chain synthetic polymers composed of at least 85% ester units, most commonly polyethylene terephthalate (PET). PET is produced via the reaction of terephthalic acid and ethylene glycol. Polyester fibers are strong, durable, resistant to moisture and chemicals, and can be manufactured into filaments or staple fibers. They are widely used to make clothing, home furnishings, industrial products, and frequently blended with other fibers like cotton and wool.

1. Polyester
Polyester
Polyester fibres are formed from synthetic polymers, manufactured by the action of polyfunctional
acids with polyfunctional alcohols. The fibre forming polymer substance is a long linear polymer with
repeating ester groups in its structure.
According to “FTC (Federal Trade Commission of USA)”, Polyester fibres are manufactured fibers in
which the fiber forming substance is any long chain synthetic polymer composed of at least 85% by
weight of an ester of a substituted aromatic carboxylic acid, including but not restricted to substituted
Terephthalate units P(-R-O-CO-C6H4-CO-O-) and para-substituted hydroxybenzoate units P(-R-O-CO-
C6H4-CO-O-).DuPont Company of USA first produced polyester fibres on commercial scale in 1953.
Commercial or trade names of polyester
• Terelene (UK)
• Dacron (USA)
• Tetron (Japan)
• Torital (Italy)
• Lavson (Russia)
• Terenca (Holland)
• Diolen (France)
Classification of Polyester fibres and their manufacturing process
There are different types of polyester-
Polyethylene terephthalate (PET)
The most important and widely used polyester is known as polyethylene terephthalate. It is produced
from the polymer manufactured by the reaction of terephthalic acid (TPA) and ethylene glycol (EG).
The reaction can be shown as below-
n HOOC- --COOH + n OH-CH2-CH2-OH HO-[-OC- -COO-(CH2)2O-]n-H
TPA EG PET or Dacron
+ (2n-1) H2O
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2. In USA, PET is known as Dacron but in UK, it is known as Terylene and produced from the polymer
manufactured by the reaction of dimethyl terephthalate (DMT) and ethylene glycol (EG) as shown
below-
n CH3OOC- --COOCH3 + n OH-CH2-CH2-OH CH3O-[-OC- -COO-(CH2)2O-]n-H
DMT EG Terylene
+ (2n-1) CH3OH
Poly-1,4-cyclohexylene dimethylene terephthalate (PCDT) or Kodel II (200)
This type of polyester is derived from the polymer manufactured by the reaction of terephthalic acid
(TPA) and 1,4-cyclohexane dimethanol which can be shown as below-
n HOOC- -COOH + n HOCH2- -CH2OH
TPA
HO-[-OC- -COO-H2C- -CH2O-]n-H + (2n-1) H2O
PCDT
Vyron
For this type polyester, fibre forming polymer is produced from ethylene glycol and a mixture of
terephthalic and isophthalic acid.
m HOOC- -COOH + n HOOC- -COOH + (m+n) OH-CH2-CH2-OH
TPA EG
HO-[-OC- -COO-(CH2)2-OOC- -COO-(CH2)2-O-](m+n)-H
Vyron
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3. Flow chart of Polyester production
Preparation of raw material
(Terephthalic acid, DMT, ethylene glycol preparation)
Mixing tank
Polymerization in reactor
(Ester interchange and poly condensation)
Temperature: 260-2800
C, Time: 3-6 hours
Polymer chips
Melt spinning
Polyester filament produced from spinneret holes
(Monofilament, multifilament)
Drawing
Reeling onto a package or Texturization
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4. Polymer system
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5. Polyester fibre forming polymer is a long linear polymer and it’s degree of polymerization is 115 to
140 where molecular weight is around 20000. Important groups are –CH2, -CO, -OCO and held in
polymer together by Vander Walls force, H-bond. Polyester polymer length is 120 to 150µm and
0.6µm thick. It is 65 to 85% crystalline. -OH, -COOH are the functional groups of polyester.
Macro structure of polyester
Length: It can be made in both staple and filament form.
Fibre diameter: 12 to 25 µm
Length width ratio: 2000:1
Appearance: Smooth
Cross section: Generally have round cross section but may be triangle, oval and rectangle shaped.
Color: Generally white
Physical properties of polyester
Specific gravity: 1.38
Moisture Regain: 0 to 0.4% at standard condition due to having extremely crystallinity and lack of
polarity.
Tenacity (dry/wet): 7-8 gm/denier for high tenacity filament
4.5-5.5 gm/denier for normal tenacity filament
3.5-4 gm/denier for staple fibres
Elongation: 8-11% for high tenacity
15-30% for medium tenacity
25-45% for staple fibre
Bending recovery: Good
Abrasion resistance: Not good. Abrasion resistance of normal polyester is less than that of high
tenacity one.
Resiliency: very good.
Chemical properties polyester
1. Effects of moisture:
Polyester absorbs only a very small amount of moisture and the tenacity and elongation are
unaffected by moisture.
2. Effects of bleaches:Not affected by oxidizing and reducing bleaches.
3. Effects of acids:Polyester fibres are highly resistant to mineral and organic acids. Weak acid
can not effect on them even on boiling. Strong mineral acid such as H2SO4 can only hydrolyze
them on boiling for hours together.
4. Effects of alkali:Polyester is very much resistant to alkalis. Only strong hot alkalis results in a
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6. slow thinning of the diameter by saponification.
5. Effects of organic solvents:Resistant to all dry cleaning solvents.
6. Dye ability:Disperse dye and some pigments can be used for coloration.
7. Effects of sunlight:Have good resistance to sunlight but becomes weak when expose in
sunlight for long time.
Thermal properties of Polyester
Polyester fibre is the most thermally stable synthetic fibre. If heat setting is not done properly then
shrinkage occurs. At high temperature polyester melts and burns.
Softening temperature: 690
C
Melting temperature: 250-2650
C
Sticking temperature: 230-2400
C
Ironing temperature: 1350
C
Thermo plasticity
‘Thermo plasticity’ means capable of being shaped or moulded when heated. Thermoplastic
fibres heated under strictly controlled temperatures soften and can then be made to conform to a flat,
creased or pleated configuration. When cooled, thermoplastic fibres will retain the desired
configuration that is remain flat, pleated or creased. Polyester textile materials can be permanently
heated. Textile fibres classed as thermoplastic are acetate, triacetate, acrylic, nylon and polyester.
Polyesters retain a heat set permanently where as acetate fibres do not hold a set as satisfactory.
Biological properties of Polyester
Polyesters have good resistance against micro organisms, larvae, fungi, mildew and moulds.
End uses of Polyester
01. As apparel:
Men’s wear, women’s wear, children’s wear, trousers, skirts, suits, jackets, blouses and every form of
clothing are made by polyester fibres. Besides ties, lingeries etc can also be made by polyester fibres.
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7. 02. As blended fabrics:
Polyesters are widely used in blends with cotton, wool, acrylic, nylon etc fibres for making quality
fabrics. Blends with cotton and virgin wool are very popular. They are often referred to as the
"classical blend". This is normally a combination of 55% polyester and 45% wool.
03. As home furnishings:
Carpets, curtains, draperies, sheets, pillow covers, wall coverings, upholstery etc are made of polyester
fibres.
04. As industrial use:
Polyester fibres are used in manufacturing of tire cord, power belt, ropes, tarpaulin, nets, hoses,
conveyor belt etc. It is also used in making floppy disk, liners etc.
Use of polyester higher than any other synthetic fibre
The use of polyester is higher than any other synthetic fibre due to low cost, more durable, no
fading, easy care, no ironing.
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