Introduction to Polymer Science
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Polymer:
The word
polymers are derived from the Greek word poly means many and mers means unit or
part. Polymers are chemical substances having very high molecular weight.
Molecular weights of ordinary chemical substances are counted in ten or
thousands. Whenever Molecular weight of
polymers are counted in thousands and
hundreds of thousands, because of the big size of the polymer molecules. They
sometimes referred to as macro or giant molecules. They are built up of many small
molecules joined together by chemical bonds.
Example polyethylene
Monomer:
The word Monomer
is derived from the Greek word Mono means one and mers means unit or part.
Polymers are chemical substances having very high molecular weight. The small
molecules of the substances from which a polymer is found is called Monomer or
Monomers are low molecular weight compounds having a functionality of two or
more are called Monomers.
Example ethylene
Polymerisation:
The chemical reaction by which monomer or in the case of
co-polymerisation more than one monomer is converted to polymer is called
polymerisation. Most generally the reaction may be represented as
Where n is the
degree of polymerisation usually n
has high values.
Repeat unit:
The structural unit enclosed by brackets is referred to as
the repeat unit/monomeric unit.
End group:
End groups are the terminal units that terminate polymer
chain where end groups are specified they are shown outside the brackets.
e.g.: CH3 – CH2 (CH2 – CH2)n –
CH = CH2 End group.
D.P.→The degree of polymerisation refers to the total no of
structural units including end groups and hence is related to both chain length
and molecular a weight of the structural unit.
Monomer residue:
The remaining part of the monomer that is present in the
polymer is called monomer residue.
The importance of polymer science to
study for textile engineering:
(1)
Textile fibres are polymeric substance.
(2)
Size materials are polymer (used in weaving).
(3)
Printing thickeners are polymers.
(4)
Binders and fixers used in coloration with
pigments are also polymers.
(5)
Many of finishing applied on textile goods are
based on polymers.
(6)
Polymers are also used as wet processing aids.
Difference between
polymer and ordinary chemical substance:
Properties
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Polymer
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Ordinary
chemical
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Molecular
weight
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High
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Low
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Dissolution
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Slow,long
time
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Quick,
less time
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Solution
viscosity
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Very
high
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Low
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Melting
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Range
of melting temperature
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Short
melting temperature
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How do we write the
name of a polymer?
If the name of monomer remain one words the
name of the polymer is obtained by prefixing the word “poly” to the name of the
monomer, such as polyethylene, polypropylene. If the name of the monomer
consists of two or more words then we write the name of the polymer by poly (
name of the monomer) and poly ( poly vinyl, vinyl chloride)
