Section 1 of 4Everyday Uses
Polymers are chosen for each use because of properties such as their flexibility, water resistance and ability to be shaped.
Packaging
- Polymers are light and cheap, and they are widely used to package food and drink.
Waterproof coatings
- A polymer coating can make fabric waterproof while keeping the fabric flexible.
Dental and medical
- Polymers can be formed into specific shapes, which is why they are used in dental polymers and wound dressings.
Hydrogels
- Polymers that absorb large amounts of water and swell, used in nappies and in granules added to soil.
Protection
- Polymer materials can be used to cover and protect injuries, such as in wound dressings, while the body heals.
Section 2 of 4Smart Materials
Smart materials can have their properties changed in a reversible way.
1
Smart materials are materials whose properties can be changed reversibly by changing the conditions around them.
2
Shape-memory polymers can be bent out of their original shape but return to it when they are heated.
3
Shape-memory polymers are used in car bumpers, so that a dent caused by a collision can be recovered by heating.
4
Shape-memory polymers are also used in helmets and mouthguards, which return to their original shape after being deformed.
Section 3 of 4Hydrogels in Detail
Hydrogels in Detail
Absorption
- Hydrogels take in large amounts of water, many times their own size, as water molecules weakly join to the polymer chains.
Swelling
- The gel swells as it takes up water, which makes it useful for holding water.
Release
- When placed in dry conditions, the hydrogel releases its water slowly.
Uses
- Hydrogels are used in nappies and in granules added to soil to help plants retain water.
Section 4 of 4Exam Checklist & Tips
10.4.3 – Key Points for the Exam
- Smart material A material whose properties can be changed in a reversible way by changing its conditions.
- Shape-memory polymer A smart polymer that returns to its original shape when it is heated.
- Hydrogel A polymer that absorbs large amounts of water and swells without dissolving.
- Reversible change A change that can be undone by returning the conditions to their original state.
Common Mistakes
- Saying that smart materials change permanently; their change is reversible.
- Describing a hydrogel as a polymer that dissolves in water; it absorbs water and swells instead.
- Assuming all polymers are waterproof and heat resistant;
- each polymer is chosen for the properties its use needs.
- Describing a use without linking it to the property that makes the polymer suitable.