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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