1. Lesson Outcomes Polymers
All must Describe LD and HD polythene and production
Describe thermosoftening and thermosetting polymers
Most Should
Explain properties in terms of bonding between polymer chains.

2. Polymers Describe LD and HD polythene and production from monomers.
Describe thermosoftening and thermosetting polymers (D-C)
State advantages and disadvantages of using polymers.
Explain properties in terms of bonding between polymer chains. (B-A*)

3. Polymers
CHEMISTRY 2
GCSE Additional Science
Chapter 9

4. Properties of Polymers
Poly(ethene) and other polymers are simple molecular structures with covalent bonds within the molecule but only weak forces of attraction between the molecules.
This gives them the typical properties of simple molecular structures.
In poly(ethene), the long molecules lie side by side. These can uncoil and slide past each other, making the material flexible.
Long polymer chains have stronger forces of attraction than shorter ones. By making the chains of a polymer longer, a stronger and less flexible material is produced.

5. Low Density Polythene Low-density polyethene
The side branches stop the polymer molecules from lining up regularly. Its structure is not crystalline.
This means that:
the material has a lower density than HDPE
the forces of attraction between polymer molecules are weakened
the material is less strong, and has a lower melting point, than HDPE
Made using high pressure ( up to 3000 atmospheres) and moderate temperature ( about 300oC)

6. High Density Polythene
The polymer molecules line up regularly to give a crystalline structure.
This means that:
the material has a higher density than LDPE
the forces of attraction between polymer molecules are strong
the material is stronger, and has a higher melting point, than LDPE .
Made using a catalyst, 100 oC and normal atmospheric pressure

7. Thermoplastics and thermosets
Thermoplastics is the name given to plastics that melt when heated. Can be melted and reshaped many times. They are used to make bowls, buckets and clingfilm.
Thermosets is the name given to plastics that do not soften when heated so can be moulded only once. They are used to make saucepan handles and electrical fittings.
The difference:-
Thermoplastics
Thermosets
GCSE Additional Science
Chapter 9
Thermoplastics are long chains with weak forces between them. These chains slip easily over each other, so they are flexible. They melt when heated gently because the weak forces need little energy to break.
The chains are connected by cross-links within a thermoset. They do not slip over each other easily so are more rigid than thermoplastics. A lot of heat energy is needed to break the cross-links, so they do not soften (melt) when heated.

8. Advantages and Disadvantages of Polymers
Cheap
Advantages
Made from a
non-renewable
resource
Disadvantages
Traps and kills
Animals when
it’s litter
Do not corrode
Light
Use less energy
to make than
traditional
materials
Easy to mould
into different
shapes
Many are non-biodegradable
Polymers
Creates rubbish and
pollution
GCSE Additional Science
Water doesn’t
affect them
Strong for
their weight
Chapter 9
Must recycle them
to maintain clean
environment
Suitable for a
wide variety of uses