Ceramics, Composites, and Polymers
Ceramics
CERAMICS are non-metal solids with HIGH MELTING POINTS and are not made from carbon-based compounds.
Some CERAMICS are made from WET CLAY, which can be found in the ground and moulded into various shapes.
When HEATED in a FURNACE at high temperatures, clay hardens into ceramics, which can be used to make POTTERY and BRICKS.
An example of a TRANSPARENT ceramic is GLASS and there are TWO types:
1. SODA-LIME GLASS: made by heating a mixture of LIMESTONE, SAND, and SODIUM CARBONATE.
2. BOROSILICATE GLASS: also made of LIMESTONE, SAND and SODIUM CARBONATE but also includes BORON TRIOXIDE which gives it a HIGHER MELTING POINT than soda-lime glass.
Composites
Most COMPOSITES are made of TWO materials. A MATRIX (acting as a binder) surrounding and binding together FIBRES (fragments) of the other material, which is called the REINFORCEMENT. This structure makes the composite STRONGER and HARDER.
Examples of composites include:
1. FIBERGLASS: Features glass fibers in a polymer matrix, noted for its low DENSITY and high STRENGTH, suitable for vehicles and sporting equipment.
2. CARBON FIBRE COMPOSITES: Use a polymer matrix reinforced with carbon fibers or carbon atom chains, offering strength and lightness for aerospace and automotive applications.
3. CONCRETE: A composite of sand and gravel (AGGREGATE) in cement, ideal for building materials due to its robustness.
4. WOOD: A NATURAL composite of CELLULOSE FIBRES held together by an organic polymer matrix, used widely in construction and furniture.
Polymers
The properties of polymers depend on
- What MONOMERS they are made from.
- The CONDITIONS under which they are made, such as TEMPERATURE and PRESSURE.
An example is HIGH-DENSITY and LOW-DENSITY poly(ethene) which is made by POLYMERISING ethene.
LOW DENSITY (LD) POLYETHENE: Produced at MODERATE temperatures and pressures. More FLEXIBLE and used for bags and bottles.
HIGH DENSITY (HD) POLYETHENE: Produced at HIGHER temperatures and pressures. A more RIGID polymer used for water tanks and pipes.
All polymers can be divided into THERMOSOFTENING and THERMOSETTING polymers:
THERMOSOFTENING POLYMERS: These MELT when they are heated meaning can be reheated and RESHAPED, offering flexibility in manufacturing and recycling.
THERMOSETTING POLYMERS: These DON'T MELT when heated making them suitable for heat-resistant applications.