1. Polymers

2. Latin: Plasticus, that which can be molded
Polymer
This name hints at how polymers are made
Many Parts
PLASTICS
This name honors plastics useful property of being easily molded
Latin: Plasticus, that which can be molded

3. Polymer
Polymers are made up of many many molecules Poly- means "many" and -mer means “unit”

4. Polymers: Introduction
If a Monomer = A
then Polymer = A-A-A-A-A-A-A-A-A-A-A-A-A-A-A-
Ex:
C=C C=C C=C    -C-C-C-C-C-C
monomer monomer monomer polymer (plastic)
Note:
Only one product
Occurs with alkenes

5. POLYMERISATION A process in which small molecules called monomers join
together into a large molecule.
There are 2 basic types
ADDITION : made from alkenes using an Addition reaction.
And all the atoms in the monomer are used to form the polymer
CONDENSATION monomers join up the with expulsion of
Small molecules not all the original atoms are present in the polymer

6. POLYMERISATION OF ALKENES ADDITION POLYMERISATION
The equation shows the original monomer and the repeating unit in the polymer
ethene poly(ethene)
MONOMER POLYMER
n represents a large number

7. Polyethylene.
Polyethylene. It is the most common plastic you see.
It is used for bottles, buckets, jugs, containers, toys, even synthetic lumber, and many other things.

8. There are two types of polyethylene polymers (plastics).
HDPE, called high density polyethylene, with long straight chains as long as 20,000 carbons (shown here). It is hard.
The other LDPE has many branching chains and is soft

10. HDPE

12. Polymerisation of Ethene

13. Another polymer, which is almost the same as polyethylene, is PolyVinyl Chloride or PVC. The difference is that every other hydrogen is replaced with a chlorine atom (green sphere).

14. POLYMERISATION OF ALKENES ADDITION POLYMERISATION
Chemical Properties
Fairly inert. This means it is resistant to chemical attack and
2) it is non-biodegradable.
3) VERY large molecules so they have a lot of INTERMOLECULAR forces…..what property does this give them?

15. POLYMER PROPERTIES
Plastics are all solid at room temperature, why?
These molecules are VERY large so intermolecular forces are huge.
so polymers are solid at room temperature.
The carbon–carbon covalent bonds are strong and there are
so very many, so plastics are NOT chemically reactive.
The physical properties come from weak intermolecular
Forces, but here are many of these too, thus plastics melt but ay a fairly high temperatures Ex: 150 0C (polyethene). Unless they are cross bridged (we talk later)
2. Why do plastics melt rather than react?

16. DIFFERENT KINDS OF PLASTIC EXAMPLES OF ADDITION POLYMERISATION
ETHENE
POLY(ETHENE)
PROPENE
POLY(PROPENE)
CHLOROETHENE
POLY(CHLOROETHENE)
POLYVINYLCHLORIDE PVC
TETRAFLUOROETHENE
POLY(TETRAFLUOROETHENE)
PTFE “Teflon”

17. POLYMERISATION OF ALKENES
SPOTTING THE MONOMER

18. POLYMERISATION OF ALKENES
SPOTTING THE MONOMER

19. Polymerisation of Propene

20. Thermosetting V Thermosoftening Polymers
Thermosetting Polymer
Thermosoftening polymers
cannot be reshaped.
If heated it will burn, not re-melt
polymer chains joined by cross-links
 can be reshaped when heated up again.
Polymer chains are not linked

21. NATURAL POLYMER
Cellulose made of chains of the sugar, although not by addition reactions

22. Plastic can be bad

23. Plastics Uses and Problems

24. Disadvantages of Plastic
Most plastics are non-biodegradable.
2) During combustion toxic fumes are released.
3) Plastics are made from fossil fuels which are non-renewable

25. Burning some plastics is bad (CH2CHCl)n + O2  CO2 + CO + HCl + H2O
PVC pipes are safe until it burns. The chlorines in the PVC combine with the hydrogen atoms in the PVC to form hydrogen chloride gas (HCl).
When this contacts water in lungs or mouth, it turns to hydrochloric acid (HCl(aq)).

26. They are cheap and easy to make. They don’t oxidize (rust).
Advantages of Plastics
They are cheap and easy to make.
They don’t oxidize (rust).
Plastics are resistant to chemical attack
They are easy to mould into shape and colour
They last a lot longer than many metals .

27. Biodegradable Plastics
Instead of using fossil fuel derived monomers for polymerization,
Starch from foods (corn starch or potato starch can be used, they
can polymerize and form plastics as well as ethene or propene.
Advantage: pollution control as these will rot in less than a year
Disadvantage: using food when the world still has hungry
people is grossly unethical. These plastics do not work as well

28. Plastics How They are Made

29. Quiz

31. STOPPING POLYMERIZATION REACTIONS
How can the polymerization reaction end or be stopped?
Run out or reactants (monomers)
ii) 2 free radial monomers combine head to head
iii) Addition of chain terminating agent such as nitro benzene
IV) Oxygen impurities is often a chain terminator, The growing chain will react with molecular oxygen, producing an oxygen radical, which is much less reactive.
V) The radical chain reacts with a hydrogen the chain, as it does above with oxygen
INITIATION, free radical formation via a catalyst benzoyl peroxide
PROPAGATION, the reaction keeps going when the ethene forms a free radical upon collision with benzoyl peroxide
TERMINATION 5 ways