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Properties and Uses of Polymers
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Plastic properties
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A world of plastic
How many different uses of plastic can you spot?
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What are the properties of plastics?
Plastics are all different, but they share a few
general properties:
They do not conduct electricity and
are poor conductors of heat.
They are unreactive – most are not
affected by water or air, and many
are not affected by chemicals.
Why is the unreactivity of plastics
both useful and problematic?
Their unreactivity makes plastics durable and able to safely
contain and protect many substances. However, it also means
that they persist in the environment for a long time.
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lined-up chains
make plastics
dense, rigid and
harder to melt
(e.g. high-density
polyethene).
The properties of plastics depend greatly on how the
polymer chains are arranged and held together:
branching chains
make plastics
light, soft and
easy to melt
(e.g. low-density
polyethene)
What makes plastics different?
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Changing the properties of plastics
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Thermosetting and thermosoftening plastics
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uPVC is perfect for window
frames as it is strong, light
and durable.
uPVC chains
chains packed
tightly together
The ‘u’ stands for
unplasticized, and means
the polymer is rigid.
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Adding a plasticizer lets the chains slide.
Oiling the chains?
plasticizer
How will the plasticizer change the polymer’s properties?
The polymer will be flexible, not rigid.
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Matching polymers to their uses
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Polymers, plastics and properties
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Designer materials
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New polymers
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Breathable fabrics are designed
to keep the wearer warm and
dry in extreme weather, but still
allow sweat to escape.
GORE-TEX® is a breathable
fabric made from a microporous
membrane made from expanded
polytetrafluoroethene (ePTFE).
What are breathable fabrics?
It is coated with a special covering to protect against oils,
cosmetics and other substances that could cause damage.
The ePTFE is very fragile, so it is laminated between
layers of nylon or polyester for added strength.
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How does GORE-TEX® work?
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Discovering Kevlar®
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In bullet-proof vest, several layers of Kevlar® fibres are
tightly interlaced with each other and sandwiched between
layers of plastic film.
As this happens, each fibre extends horizontally and vertically,
distributing the impact over the whole fibre network.
When a bullet or other object strikes the vest, it pushes back
on the Kevlar® fibres at the point of impact.
These layers are then
woven to an outer
layer of normal
‘carrier’ fabric.
Kevlar® fibres and bullet-proof vests
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How do bullet-proof vests work?
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Using Kevlar®
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Summary activities
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Glossary
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Anagrams
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Multiple-choice quiz