Uses of Polymers

Section 1 of 6Where polymers are used

Packaging

• Packaging New polymer materials are developed to keep food fresh, protect goods and reduce weight.
• They can be made flexible, strong or transparent depending on need.

Coatings and medicine

• Coatings and medicine Waterproof polymer coatings are applied to fabrics so that rain runs off.
• Dental polymers fill and repair teeth, and polymer wound dressings protect injuries while letting them heal.

Advanced materials

• Advanced materials Hydrogels and smart materials such as shape-memory polymers are examples of modern polymers designed for particular jobs.

Section 2 of 6Smart materials

1Starting state

• Starting state The material has a particular shape or property.

2Stimulus

• Stimulus A change in conditions, such as heating, alters the material.

3Change

• Change The property or shape changes in a reversible way.

4Return

• Return When the original conditions come back, the material reverts to its first state.

Section 3 of 6Hydrogels and shape-memory polymers

Type	How it behaves	Uses
Hydrogel	Absorbs up to about 1000 times its own volume of water because water molecules attach weakly to the polymer chains and the gel swells; it releases the water slowly in dry conditions	Nappies, granules mixed into soil to help plants retain water, wound dressings
Shape-memory polymer	Can be bent or deformed, then returns to its original shape when heated	Car bumpers, helmets, gum-shields

Section 4 of 6Linking property to use

Why that polymer?

Absorbency

• Absorbency A hydrogel can hold large amounts of liquid, so it is suited to nappies and to keeping soil moist.

Recovery of shape

• Recovery of shape After a dent, heating lets a shape-memory bumper return to its design shape, so it can be repaired.

Waterproofing

• Waterproofing A thin polymer layer stops water entering fabric while the cloth stays light.

Biological safety

• Biological safety Dental and wound polymers must not be toxic and must be safe in contact with the body.

Section 5 of 6Key terms

Term	Meaning
Smart material	A material whose properties change reversibly when conditions change.
Hydrogel	A polymer that can absorb very large amounts of water and swell.
Shape-memory polymer	A polymer that can be deformed but returns to its original shape when heated.
Polymer coating	A thin layer of polymer applied to a surface, for example to make a fabric waterproof.
Reversible change	A change that can be undone when the original conditions are restored.

Section 6 of 6Exam technique

1

Saying a smart material changes permanently; the key idea is that the change is reversible.

2

Stating that a hydrogel dissolves in water instead of absorbing it and swelling.

3

Claiming shape-memory polymers go back to shape when cooled; the example in this topic returns when heated.

4

Trying to memorise named examples of new materials; you should be able to consider uses of new materials from the information given.

5

Giving a use without linking it to the property that makes the polymer suitable.