1. Polymers
Chapter 21

2. Introduction What is a polymer?
A very large molecule made up of identical smaller units (minimum 50), which repeat.
Monomer? The small identical units.
Plastic: polymers of organic molecules
Examples of plastics: PVC, PET, Polythene, polyester

3. Addition Polymerisation
Alkenes are able to react together and form polymers: Why?
C=C double bonds: these can break open and bond together.
Where do we get these alkenes from?
Cracking of large molecules in crude oil.
Heat, high pressure, and an initiator are needed.
Initiator is not a catalyst.
The initiator is not left unchanged at the end of the reaction, but gets bonded to the ends of the molecule.

4. Poly(e)thene Polymer of ethene
Chain varies from C atoms in length

5. Uses of polythene
Low-density (LDPE): ethane compressed, 200C, with O2, molecular mass: 50, ,000. Thin, flexible, not strong: plastic bags.
High density (HDPE): Zieger catalyst (titanium), molecular mass 50, million. Stronger, more rigid: plastic milk bottles.

6. Polypropene Polymer of propene: addition polymerisation
Stronger than polythene
Ropes and crates

7. PVC Polymer of chloroethene (old name vinyl chloride) Strong, rigid
Electrical insulation, drainpipes, plastic sheets, clothing (with added chemicals to make it more flexible)

8. PET
Polyethylene terephthalate

9. Condensation Polymerization
Polymers can also be made by joining two different types of molecules together.
They react together and a small molecule, usually water, is lost (hence the name).
What examples do you already know?

10. Making nylon