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IGCSE AQA Design and Technology
Specialist : Materials
Polymers
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Eleanor Rumpf
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Cards (43)
Toughness is the ability to withstand a
sudden impact
Hardness is the ability of a material to withstand
scratching
,
cutting
and
abrasion
(wear)
Polymers are produced
industrially
through a process known as
polymerisation
Synthetic polymers are made from
hydrocarbons
Composition of the
polymers
can be adjusted to create
different properties
for specific
purposes
Two types of polymers:
thermosetting
and
thermoforming
Thermosetting polymers cannot be
recycled
Thermosetting polymers form
cross-links
between
chains
(ER)
Epoxy Resin
Good
electrical
insulator
hard
brittle unless reinforced
resists chemicals well
USED FOR
adhesives
casting
encapsulation
(eg:
laminating paper
)
(PF)
Phenol-Formaldehyde
Hard
Strong
heat
and
chemical
resistant
good
electrical
insulator
limited colours available
USED FOR
Bowling balls
Saucepan Handles
(MF)
Melamine-Formaldehyde
Stiff
hard
strong
resists
some
chemicals
and
stains
USED FOR
Laminates
for
work surfaces
Hawker Centre
tableware
Electrical insulation
(PR)
Polyester Resin
Brittle
but becomes tough when
laminated
with glass fibre
good
compressive
and
tensile
strength
hard
UV
resistant
USED FOR
GRP boats
Car Body Panels
(UF)
Urea-Formaldehyde
Stiff
hard
strong
brittle
good
electrical
insulator
USED FOR
Adhesives
(
MDF
)
Electrical Fittings
ER =
Epoxy Resin
PR =
Polyester Resin
MF =
Melamine Formaldehyde
PF =
Phenol Formaldehyde
UF =
Urea Formaldehyde
(7) =
Acrylic
(6) =
High Impact Polystyrene
HIPS
(3) =
Polyvinyl Chloride
PVC
(1) =
Polyethylene Terephthalate
PET
(5) =
Polypropylene
PP
(4) = Low Density Polyethylene LDPE
Heating weakens the
join
and
softens
the
polymer
, which means it can be
reshaped
by
heating.
As the
plastic cools
, it
hardens
to a
permanent shape
Polypropylene -
Fatigue
and
moisture
resistance
Polyethylene Terephthalate - High
Tensile
Strength,
food safe
High-Density Polythene - Excellent
Chemical
Resistance, Able to be
Sterilised
Polyvinyl Chloride - Can be
rigid
or
flexible
,
Hard
(
resistant
to
scratching
)
Polyvinyl Chloride - think of
vinyl
record
High Impact Polystyrene -
Fusibility
(easy to
mould
),
Lightweight
,
resistance
to
moisture
Low Density Polythene - used for
toothpaste container
,
ketchup bottles
PET used for
food packaging
,
fibres
for
clothing
and
plastic waterbottles
PP (most common plastic) used for
chairs
,
toys
and
bottle caps
HDPE used for
buckets
,
tubing
and
washing up bowls
PVC used for Water
pipes
,
raincoats
and
window frames
PPMA used for
Signs
,
Aircraft canopies
and
baths
HIPS used for
yogurt pots
,
refrigerator
and
vacuum-formed packaging
Combining polymers with other materials can
reinforce
them (make them
stronger
) by
combining
the properties of both materials
usually,
thermosetting polymers
(typically
epoxy
) are used because they come in a
liquid
state and can
impregnate
and
form
around the second material
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