2. Polyamides
A polyamide is a polymer family that contains recurring amide
groups of: R-CO-NH-R’
as integral parts of the main polymer compound.
They are formed either by the polymerization of an amino
acid or the condensation of a polyamine with a
carboxylic acid in which the structural units are linked by
amide group bonding them together.
Introduction
Nylon
Chemistry
Applications
Kevlar
Chemistry
Applications
Nomex
Chemistry
Applications
3. Polyamides
History
Nylon => Developed in the 1930’s at DuPont by Wallace
Carothers and his team of researchers.
Nylon is formed by the condensation reaction of two
components:
Diamine (a compound containing two amino [NH2]
groups—e.g., hexamethylenediamine)
Dicarboxylic acid (containing two carboxyl [CO−OH]
groups—e.g., adipic acid)
Or may be formed by the self-condensation of an amino acid
or an amino-acid derivative.
Introduction
Nylon
Chemistry
Applications
Kevlar
Chemistry
Applications
Nomex
Chemistry
Applications
Nylon
7. Polyamides
Introduction
Nylon
Chemistry
Applications
Kevlar
Chemistry
Applications
Nomex
Chemistry
Applications
Kevlar => In the early 1960s, DuPont was interested in
developing
“super fibers” due to the prior valuable invention of nylon,
In 1965, research scientist Stephanie Kwolek from
DuPont discovered “kevlar”
Kevlar is formed by condensation reaction of two
components:
Para-phenylene diamine
Terephthaloyl (PPD-T) chloride
Kevlar
A B
9. Polyamides
Introduction
Nylon
Chemistry
Applications
Kevlar
Chemistry
Applications
Nomex
Chemistry
Applications
Nomex=> material developed in the early 1960s by DuPont
and first marketed in 1967
- An inherently flame-resistant, high-temperature fiber
- It is sold in both fiber and sheet forms and is used as a fabric
wherever resistance from heat and flame is required,
- Nomex is formed by condensation reaction of two
components:
Para-phenylene diamine
Terephthaloyl (PPD-T) chloride
Nomex
A B
11. Polyesters
Polyester fibres are formed from synthetic polymers,
manufactured by the action of poly-functional acids with
poly-functional alcohols.
Introduction
Physical Properties
Chemistry
Uses of Polyesters
As Fibres
As Films
As Packaging
Manufacture of PET
Production of monomer
Polymerization of Polymer
12. Polyesters
Polyesters are extremely important polymers. Their most
familiar applications are in clothing, food packaging and
plastic water and carbonated soft drinks bottles.
The most used of the polyesters has the formula:
Being an ester, it is made from an acid, benzene-1,4-
dicarboxylic acid (terephthalic acid), and an alcohol, ethane-
1,2-diol.
Introduction
Physical Properties
Chemistry
Uses of Polyesters
As Fibres
As Films
As Packaging
Manufacture of PET
Production of monomer
Polymerization of Polymer
13. Polyesters
The different uses of polyesters depend on their structure.
The benzene rings in the molecular chain give them a rigid
structure, leading to high melting points (over 500 K) and
great strength.
They do not discolour in light.
Introduction
Physical Properties
Chemistry
Uses of Polyesters
As Fibres
As Films
As Packaging
Manufacture of PET
Production of monomer
Polymerization of Polymer
14. Polyesters
The polyester is produced as small granules. These are
melted and squeezed through fine holes and the resulting
filaments spun to form a fibre.
This fibre, commonly known as Terylene or Dacron, is widely
used in clothing (for example, in suits, shirts and skirts) either
alone or in blends with other manufactured or natural fibres,
principally cotton.
It is also used for filling anoraks and bedding duvets to give
good heat insulation. Other uses include car tyre cords,
conveyor belts and hoses, where its strength and resistance
to wear are paramount.
Introduction
Physical Properties
Chemistry
Uses of Polyesters
As Fibres
As Films
As Packaging
Manufacture of PET
Production of monomer
Polymerization of Polymer
15. Polyesters
The polyester can also be made into thin films which can be
used in:
food packaging, audio and video tapes, electrical insulation,
and X-ray films.
Introduction
Physical Properties
Chemistry
Uses of Polyesters
As Fibres
As Films
As Packaging
Manufacture of PET
Production of monomer
Polymerization of Polymer
16. Polyesters
A relatively newer use is for packaging, for example for
bottles (see Figure 3).
The small granules of the polyester are heated to about 500 K
and further polymerization takes place. This heating is
sometimes called solid-state polymerizing. The polymer is
melted, moulded and then stretched. The molecules are now
orientated in three directions giving the plastic great strength.
Introduction
Physical Properties
Chemistry
Uses of Polyesters
As Fibres
As Films
As Packaging
Manufacture of PET
Production of monomer
Polymerization of Polymer
17. Polyesters
Ethane-1,2-diol is reacted with benzene-1,4-dicarboxylic acid
(sometimes known as terephthalic acid), or its dimethyl ester,
in the presence of a catalyst, to produce initially the
monomer and low molecular mass oligomers (containing up
to about 5 monomer units).
Using the acid provides a direct esterification reaction, while
the dimethyl ester reaction involves ester interchange. The
dimethyl ester route requires the use of an acid catalyst
whereas direct esterification is self-catalysed by the
carboxylic acid groups.
The dimethyl ester route was originally preferred because the
ester could be purified more readily than the acid. Very pure
acid is now available in large commercial quantities; the
modern processes therefore start from the acid.
Introduction
Physical Properties
Chemistry
Uses of Polyesters
As Fibres
As Films
As Packaging
Manufacture of PET
Production of monomer
Polymerization of Polymer
18. Polyesters
The acid reacts directly with ethane-1,2-diol:
Introduction
Physical Properties
Chemistry
Uses of Polyesters
As Fibres
As Films
As Packaging
Manufacture of PET
Production of monomer
Polymerization of Polymer
Starting from the acid: Direct Esterification Reaction
19. Polyesters
The acid reacts with methanol to form the dimethyl ester,
with manganese(II) ethanoate being commonly used as the
catalyst.
The dimethyl ester is then reacted with ethane-1,2-diol, by a
process known as transesterification, in which one alcohol
(ethane-1,2-diol) exchanges for another (methanol)
Introduction
Physical Properties
Chemistry
Uses of Polyesters
As Fibres
As Films
As Packaging
Manufacture of PET
Production of monomer
Polymerization of Polymer
(ii) Starting from the dimethyl ester: Ester Interchange Reaction
20. Polyesters
Introduction
Physical Properties
Chemistry
Uses of Polyesters
As Fibres
As Films
As Packaging
Manufacture of PET
Production of monomer
Polymerization of Polymer
Granules of PET
21. Polyesters
The monomer then undergoes polycondensation with the
elimination of ethane-1,2-diol, a condensation reaction:
Introduction
Physical Properties
Chemistry
Uses of Polyesters
As Fibres
As Films
As Packaging
Manufacture of PET
Production of monomer
Polymerization of Polymer
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