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Polyester
Polyester as the name
suggests is made out of esters. Esters are functional group with –COOR,
where R is a methyl group. Polyester is a man made fiber, which is a polymer
with esters. Polyester is a very popular yarn these days. Popular
polyester is called terylene and another name for the terylene fiber is
dracon.
Preparation
of polyester
We have seen earlier that
esters are formed when a carboxylic acid reacts with an alcohol.
Polymerization reaction can make the ester formed into long chain molecules.
| The following raw
materials are used for the manufacture of a polyester called terylene: |
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Tetraphthalic
acid
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Ethylene
glycol
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Tetraphthalic acid is a
dicarboxylic acid, that is it has two –COOH groups.
It reacts with ethylene glycol that has two –OH groups to give an
ethylene type ester. The polymerization reaction gives polyester and water.
This particular polyester is called terylene. The reaction is shown below.
Molten
or viscous terylene molecules are forced through spinneret holes in the form
of jets which gives rise to terylene threads.
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Properties
of polyesters
1.
Strength : Polyester fibers like terylene are strong as they are long
chain polymers.
2.
Elasticity : Polyester fibers are very elastic. This means that they
regain their original shape once
the load on them is released. They do not
loose their shape even after repeated use.
3.
Water absorption : Polyester fibers like terylene absorb very little
water or moisture.
4.
Wrinkle resistant : Fibers made of polyester do not wrinkle easily.
If wrinkled and released, they get
back to their original shape quickly.
5.
Abrasion resistant : polyester fibers withstand wear and tear or
abrasion much better. The basic
polyester from which it is made is long
chained molecule and is completely unreactive to external
chemicals and
biological agents. Thus clothes made from polyester are long lasting.
In addition to these
properties, polyester is also moth resistant and light in weight. The fibers
drawn from a spinneret can be made very fine and thin, thus the texture of
polyester can be very fine and smooth. Polyester is also chemically more
inert than the natural fibers and is insoluble in most common solvents.
| Uses
of polyester |
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Terylene,
a polyester is used extensively in textile industry to make clothes like
sarees, dress materials, tapestry, etc.
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Terylene
mixed with natural fibers like cotton or wool called terrycot or
terrywool, is used widely for making clothes.
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Polyester
material is light weight as well as strong. Hence it is used for making
light weight sails. Also these sails are water resistant which is useful
for sailing purposes.
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Polyester
materials are used as conveyor belts, fan belts, etc. as their elastic
properties are very good. They are also strong and long lasting.
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Carbon fibers
Long chain pure carbon
fibers attached together by covalent bonds only, are made by heating nylon
or polyester fibers. The heat treatment is done in the absence of air, hence
oxygen from these molecules are eliminated, leaving behind pure carbon
fibers. They cannot be strictly called as polymers.
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Properties
of carbon fibers
1.
Strength : Carbon fibers are strong as they are long chain molecules.
2.
Corrosion resistant : Carbon fibers are unreactive to chemical and
biological agents. They are long
lasting.
3.
Weight : carbon fibers are very light weight but strong.
| Uses
of carbon fibers |
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Carbon fibers are
used in making sports goods like racquet handles and frames. They are
light weight and strong.
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Carbon
fibers are used in making components of a spacecraft as they are
lightweight and strong.
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