Download Unit 3b - Summary notes - Uddingston Grammar School

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Sub-topic 3B – Materials and Plastics
Summary
Plastics and Synthetic Fibres
Synthetic fibres are man-made fibres e.g. polyester, polyamide and terylene.
Some synthetic fibres are PLASTICS.
Plastic
Property
y
Use
Polyamide (Nylon) tough, fairly hard, resists
wear, good resistance to
chemicals and machines
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Bearings, gear wheels, casings
for power tools, hinges for small
cupboards, curtain rail fittings and
clothing
Polypropylene
Light, hard but scratches
easily, tough, good
resistance to chemicals
Medical equipment, laboratory
equipment, 'plastic' seats, string,
rope, kitchen equipment
Polystyrene
Light, hard, stiff,
transparent, brittle, with
good water resistance
Toys, especially model kits,
packaging, 'plastic' boxes and
containers
polythene
Tough, good resistance to
chemicals, flexible, fairly soft,
good electrical insulator
Packaging, especially bottles, toys,
packaging film and bags
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When Plastics Burn

Plastics can burn to release toxic fumes
and use up a lot of oxygen in the process.
Plastic
Elements present
Toxic fumes
Poly(ethene)
Carbon and hydrogen
Carbon monoxide
Carbon, hydrogen and
Hydrogen chloride
chlorine
(acidic)
Carbon, hydrogen and
Hydrogen cyanide
nitrogen
(toxic)
Carbon and hydrogen
Dense, black smoke
P.V.C.
Polyurethane foam
Polystyrene
Biodegradable Plastics
•
Plastic packaging does not rot away and so causes major litter problems.
•
Many plastics are non-biodegradable, meaning they will not rot away naturally.
•
Plastics are now being introduced that are biodegradable e.g. Biopol
(biodegradable polymer).
•
Paper, originally used for packaging, did rot away under the action of
microbes, and is described as biodegradable.
•
BIODEGRADABLE means that the material will decay naturally.
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New Plastics Technology
Kevlar - (discovered in 1960’s)
Bullet-proof vests are made from tightly woven fibres and are much more flexible and
comfortable than hard body armour. Kevlar is used Kevlar as a protective material
because it is:

Flexible and light

Heat resistant

Five times stronger than steel
Smart Materials
Smart materials are plastic and metal items designed to instantly change their
properties when triggered by a stimulus.
Common properties that can be significantly altered in smart materials include:

Size and shape

State (solid, liquid, gas)

Viscosity

Conductivity
Different smart materials can respond to different stimuli, such as temperature,
pressure, magnetism and voltage/current.
Ceramics
Properties
Uses of ceramics
-
Extremely hard
-
Resistant to corrosion
-
Heat resistant
-
Low ductility
-
Low toughness
-
Low density
•
- used in cars,
Spark plugs
boat engines, lawnmowers,
etc. are all made out of
ceramic.
•
Different forms of ceramics
can make excellent
insulators, semiconductors,
superconductors and
magnets.
3
Monomers and Polymers
•
Plastics are long chain molecules called polymers.
•
A polymer is a very big molecule made from many small molecules called
monomers.
•
The process in which the monomers join to make a polymer is called
polymerisation.
•
The name of the polymer
can be worked out from the
name of the monomer.
•
The term “poly” is put in
front of the name of the
monomer to name the
polymer.
•
E.g. ethene is polymerised
to make polyethene.
Plastics can be made by either:1. Addition Polymerisation
2. Condensation Polymerisation
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Addition Polymerisation

Polyethene is an example of an addition polymer. It is made from the monomer ethene.

Polyethene forms when a chemical is added which breaks the double bond between the
two carbon atoms of ethene to make a very reactive unit.

Reactive units join together, end to end and a big molecule or polymer is made.

All plastics made by addition polymerisation form when the monomer units join together
to give one product, by a series of reactions in which the double bond breaks.
 When drawing a monomer it has to be in an “H” shape with the
double bond in the middle.
i.e.
H H
I
I
C=C
I
This would be an ethene monomer
I
H H
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 A propene monomer would be drawn like this
H
H
H
H
H
I
I
I
I
I
C = C
C
I
I
I
I
H
H
C
CH3
H
C = C
 Making polypropene :-
H
H
H
H
H
H
C = C
C = C
C = C
C
C
C
CH3
CH3
H
H
H
H
H
H
C
C
C
C
C
C
C
CH3
C
CH3
C
CH3
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CH3
Repeating Unit
Part of Polymer
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Condensation Polymers
Condensation polymers are any kind of polymers formed through a condensation reaction—
where molecules join together--losing small molecules of water.
Polyester is an example of a condensation polymer that contains lots of ester links.
ESTER LINK
It can be made by reacting –

alcohols with two -OH groups, one at either end of the molecules and

acids with two –COOH groups, one at either end of the molecule.
HO
OH
Diol
HO
O
O
C
C
OH
Diacid
• The acid group loses an –OH and the alcohol loses an –H to
form water and a new bond8forms between the monomer
units.
Forming a Condensation Polymer

Polyesters are a type of condensation polymer
HO
OH HO
O
O
C
C
OH HO
OH HO
O
O
C
C
OH
•
The polyester molecules can continue to grow in both directions.
•
The acid and alcohol group join together.
•
The acid group loses an –OH and the alcohol loses an –H to form water and a new
bond forms between the monomer units.
O
O
O
O
C
C O
O
O
O
C
C
O
•
These OCO groups are called ester links or ester groups.
•
These groups identify this chain as a polyester.
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O
O
O
C
C
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