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Polymers
What is a polymer?
A molecule of large molar
mass that consists of many
repeating subunits called
monomers.
What is a monomer?
A monomer is a molecule of
relatively low molar mass
that is linked with other
similar molecules to form a
polymer.
Polyamides
What are 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 or
thioamide groupings bonding them together.
Polyamides
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The monomers in polyamide are joined
together by peptide bonds, they occur both
naturally such as in proteins but mostly
synthetically such as various nylons.
Peptide bond: A peptide bond is a chemical
bond formed between two molecules when the
carboxyl group of one molecule reacts with the
amino group of the other molecule, releasing a
molecule of water. This usually occurs
between amino acids and can be seen here:
Forming a Polyamide
History of Polyamides
Polyamides have existed in nature
(proteins) longer then humans
have existed on earth. However
the first signs of polyamides
synthetically were in 1664 when a
Chinese emperor developed a
project to manufacture synthetic
yarn. Many types of polyamides
were discovered at different times
in history but they were not
recognized as such until later on.
Polyamide 6 for example was
discovered in 1936 by Paul Slack
and sold as Perlon but nylon was
truly discovered in 1933 by Dr.
Wallace Hume Carothers (as
polyamide 6.6).
Nylon
Nylons are synthetic polyamides that are in their own
family of synthetic polymers.
It is made of monomers linked by peptide bonds and is
frequently referred to as polyamide (PA).
A molecule of water is given off and the nylon is formed.
Its properties are determined by the R and R' groups in the
monomers. In nylon 6,6, R' has 6 carbon alkanes and
R has 4 carbon alkanes, but one also has to include the
two carboxyl carbons in the diacid to get the number it
donates to the chain. In Kevlar, both R and R' are benzene
rings and this shows how broad and limitless the
polyamide group is.
Industrial Fabrication of Nylon 6.6
Nylon-6,6 is made by polymerizing hexanedioic acid and 1,6diaminohexane.
Adipic Acid = Hexanedioc Acid
Hexamethylene Diamine = 1,6-diaminohexane
Nylon Polymerization Reaction
Because the hexanedioc acid is acidic and the
amine is basic, they first react together to form a
salt. The salt is then converted into nylon-6,6 by
heating it under pressure at 350°C.
Lewis Structure of the Nylon 6,6 polymer – note the amide bond
Formation of Nylon Monomers
The monomers can both be made from cyclohexane.
Oxidation of the cyclohexane opens the ring of
carbon atoms and produces a -COOH group at each
end. That gives you the hexanedioic acid.
Some of that can then be converted into the 1,6diaminohexane. The acid is treated with ammonia
to produce the ammonium salt. The ammonium salt
is heated to 350°C in the presence of hydrogen and
a nickel catalyst. This both dehydrates the salt and
reduces it to the 1,6-diaminohexane. “
(ChemGuide.com)
Disadvantages
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Advantages
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High heat resistance
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Resistant to abrasion
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Tough and resistant
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Strong chemical resistance

Flame Retardant
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Heat Stabilized
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High moisture pick-up causes
instability
Requires UV stabilization
High shrinkage in molded
sections
Low moisture resistance
limits mechanical/electrical
applications
Low resistance to strong
acids and bases
Attacked by oxidizing
agents
Applications
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Automotive Applications
 Bearings
Electrical/Electronic Applications
Clothing and Consumer Products
Housing and construction (gears)
 Industrial Applications
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Bibliography
www.wikipedia.com
www.britannica.com
http://www.chemguide.co.uk/organicprops/amides/polyamid
es.html
http://www.bpf.co.uk/bpfindustry/plastics_materials_Nylons_
PA.cfm
http://www.chemheritage.org/EducationalServices/nylon/stor
y/story03.html