Year 11 Chemistry: Chapter 8:~ Polymers
8.6 Polymers: long-chain molecules
Cotton, wool and silk are some of the naturally occurring __________ . There are many
polymers that have been developed by chemists, these are ____________ polymers.
Some examples are cling film, clothing, domestic appliances, cars, plumbing materials and
sporting equipment.
Polymers, not plastics
For chemists the word, ‘plastic’, describes a property of a material. A substance is
described as being plastic if it can be _________ into different shapes readily.
Malleable and ductile are terms used to describe the _________ properties of metals.
Liquids and gases are infinitely plastic as they take the _______ of any container.
Many polymers are plastic materials, as they can be shaped or moulded. Some polymers
are not plastic materials, they are brittle and cannot be reshaped, some examples are
light switches and power points.
8.7 Polymers: what are they?
Polymers are very large covalent molecular substances containing tens of thousands of
atoms, They are formed by joining together a great many small molecules, called
___________ (single unit) in a process called ______________.
Two main types of polymerisation processes:
 Addition polymerisation
 Condensation polymerisation
The polymers formed through addition polymerisation often have the name of the
monomer(s) included in the name of the polymer. Example: Polyethene – is formed from
the monomer _________, PVC, polyvinyl chloride is formed from the monomer
__________ . Some condensation polymers are named after the chemical bond formed
between the monomers, for example: polyesters monomers are joined together by an
_______ functional group.
Addition polymers
Covalent bonds form between the monomer molecules to produce a polymer molecule.
*Draw diagram 8.28
Suitable monomers for addition polymerisation are ______________ (saturated or
unsaturated) molecules. The double bond splits between the two carbon atoms and reacts
forming new covalent bonds.
Polyethene: an addition polymer
Polyethene was discovered by accident in England in the 1930’s. It was first used to make
cables and insulate radar aerials during World War II.
In the process of addition polymerisation , all of the atoms present in the monomer
molecules are present in the polymer molecule. The monomers are simply added.
In any particular sample of polyethene, the sizes of the molecules will vary,
Polyethene is a thermoplastic polymer. This means that it will melt when heated and can
be reshaped. This is because of the bonds between the non-polar chains are weak
___________ forces. The strong covalent bonds remain unchanged.
There are two different types of polyethene.
 High-density polyethene (HDPE): used for pipes, buckets, toys, containers and
freezer bags. Polymerisation of ethene: atmosphere pressure, using a metal oxide
catalyst and temperature of 310°C. Produce very few and small branches, making
it high density.
*Draw figure 8.29
 Low-density polyethene (LDPE): used for cling films, garbage bags, squeeze
bottles, carry bags and insulating cables. Polymerisation of ethene: high pressure
(1000-3000 atm), using oxygen to initiate the reaction and temperature of
300°C. Producing many branches making it low density.
*Draw figure 8.29
*Look at table 8.9
Structure, Properties and Applications
Two very important properties of polymers are ___________ strength and
______________ temperature.
Define:
 Tensile strength: _____________________________________________
_____________________________________________________________
 Softening Point: ______________________________________________
_____________________________________________________________
In thermo_______, both tensile strength and softening point are affected by:



Another factor that affects the properties of a polymer is ________________ .
Define:
 cross-links:
The more cross-links the more rigid the polymer. Polymers with extensive cross-links are
called _____________ . They do not soften on heating, when there is sufficient heat
they will char.
Degree of branching
Atoms in chains that are arranged regularly create crystalline regions. The more regions
of crystallinity, the greater the degree of light scattering and the less transparent the
polymer. That is why _______ is frequently ______ transparent while HDPE is not.
Nature of side groups
Polystrene (draw the structural formula of the monomer and polymer from pg 156)
The bulky ring (C6H6) prevents chains from stacking close together and forming
crystalline regions. As a result, polystrene is amporphous ( ____________ ) and
transparent and has a low density. It is quite brittle and gives a metallic ring. The bulky
ring makes it difficult for the chains to silde over each other.
Pure polystrene is too brittle for many used so it is frequently modified by the
______________ of _________ to produce ‘’ ___________________________’ eg
bicycle helmets. Polystrene foam is produced by blowing a _____ , pentane or
_______________ , through melted polystrene beads. What other properties can be
modified? _____________________________________________________
_______________________________________________________________
Arrangement of side groups
Example Polypropene: (draw the structural formula from pg 158)
 Atactic polypropene: Groups are _____________ disturbed. Properties: soft and
greasy.
 Isotactic polypropene: __________ chains. Are used to produce babies bottles
that can be sterlised in hot water without softening.
Amounts of cross-links
Extensive cross-linking
Thermsets are brittle and cannot be reformed. They ______ when heated. Thermosets
will shatter when impacted.
Occasional cross-linking
Elastomers are materials that will regain their _________ shape after being stretched
or pulled out of shape, this is known as ___________________ .
Rubber is one material which is cross-linked during manufacture to give is elastic
properties. This process is known as ____________________ . Charles Goodyear
discovered elastic properties by accident in 1843. Nowadays chemists carefully add
carefully controlled amounts of sulfur to rubber in the form of unlinked polymer chains
and heat. Sulfur atoms react with the ______________ double bonds in the chains,
forming ____________ made up of a number of sulfur atoms.
If a small amount of sulfur is used the polymer becomes more elastic. If large amounts of
sulfur are added, more extensive cross-linking results in a more rigid material. Elasticity
varies with the ___________ of ______________ between polymer chains.
*Draw diagram 8.36 on pg 159.
Customised polymers
Define:
 Copolymers:
What properties can be modified by customising polymers:







How can the polymers be altered:




Recycling plastics
Australians consume more than ____________ tonnes of plastic every year. This
includes more than 40 different plastics. The disposal of waste plastic material is a
serious issue to our society.
*Write down the 6 polymer types (just the ‘polymer type’ column) in table 8.10.






Read: pg 161 ‘ Buckyballs and nanotubes’ – this will help you with your research
assignment.
QUESTIONS: complete all questions for Chapter 8 in your timeline.