Ceramics, Polymers & Composites (AQA GCSE Chemistry)

• Polymers are poor conductors of heat and electricity, hence they are good thermal and electrical insulators
• These properties are extremely useful for insulating electrical wiring as they prevent electric shocks and overheating

The polymer polyvinyl chloride (PVC) is commonly used to insulate electrical wiring

• Depending on the manufacturing process used, the same polymer can have different properties
• Polythene for example can be made at high pressure and moderate temperature to produce low density polythene (LDP) which is used for bags and bottles where flexibility is needed
• If it is produced at lower temperatures and pressures and with the use of a catalyst, a much higher density (HDP) polythene is produced. This polymer has a more rigid, solid structure and is used to produce water tanks, mouldings, drain pipes etc
• Polymers can also be divided into thermosoftening and thermosetting polymers
• Thermosoftening polymers consist of individual chains entwined with each other with weak intermolecular forces holding the polymer chains together
• These polymers therefore have low melting points, can be melted and remoulded to form different shapes
• Thermosetting polymers on the other hand have strong cross-links between monomers on different polymer chains that hold the structure together
• These are strong and rigid structures that don’t soften under heating

• These are made from two components: reinforcement and matrix
• The reinforcement material is embedded in the matrix material which acts as a binder
• Common examples include fibreglass and steel reinforced concrete
• Wood is an example of a natural composite as it consists of cellulose fibres held together by an organic polymer mix

• The properties of composites depend on the reinforcement and matrix used so composites can be tailor engineered to meet specific needs
• Carbon fibres for example are extremely strong and low weight, hence they are used in aviation, aeronautics and for making professional racing bicycles
• Steel reinforced concrete has immense tensile and compressive strength allowing it to be used as columns and supporting structures in construction