which have lined up and crystallised in the pink region.
gcsescience.com 59 gcsescience.com
Structure of Polymers.
Polymers may be classified as thermosoftening or thermosetting.
Thermosoftening polymers are sometimes
called thermoplastic.
Thermosoftening polymers include poly(ethene), poly(propene),
poly(styrene) and poly vinyl chloride.
A polymer
molecule is a long chain of
carbon atoms
which are held together by strong covalent bonds.
The forces in between the molecules
are relatively weak but
sections of the chains can sometimes line up side by side to form tiny crystals.
These crystals form links between the chains and hold the structure together.
When the polymer is heated the
crystals will melt,
the material will become very soft and
can flow slowly like a thick
liquid.
In this state the polymer can fill a
mould and be cast into a shape.
When the polymer cools down,
new crystals can form between the chains
and the new shape is fixed.
The same polymer can be reheated and remoulded.
Such polymers are called thermosoftening
(meaning that they go soft when you
heat them).
The picture below shows the
tangled polymer
chains
which have lined up and crystallised
in the pink region.
Some polymers do not form
crystals.
They soften when heated and harden
when cooled down again.
When cold, they are not crystalline but glassy.
These polymers are also called
thermosoftening.
Headings Polymers Search Questions 
gcsescience.com Contents The Periodic Table Index Quizzes gcsescience.com
Copyright © 2008 Dr. Colin France. All Rights Reserved.