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DT topic 4
polymers
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Cards (15)
Thermoforming-
plastic becomes
soft
and
flexible
when
heated
Join to form
long polymer chains
(no
fixed structure
or
pattern
)
thermoforming:
Pros and cons: It can be
repeatedly heated
and
moulded
Not suitable for
hot areas
or
UV sensitivity
Each time
plastic
is
reheated
it it will try to return to its
original shape
(
plastic memory
)
Good surface finish
can be achieved
Recycled easily
(reused as it can
reshaped
)
Thermosetting-
cannot be
reformed
once set to
shape
(
melamine formaldehyde
)
Chains
of polymers resulting in a (
cross linked
)
rigid molecular structure
thermosetting
:
Pros
and
cons
:
hard
and
durable
with
good structural rigidity
Can
withstand high temperature
Good electrical insulator
Cannot
be
remoulded
Burns
if
reheated
Used to
make composite materials
Vacuum forming- heat plastic
until
softened
and
draping
into
mould.
Vacuum sucks
plastic
into
mould
then is
ejected
from the
mould.
Blow moulding- blow
into
mould
and set in
shape.
Injection moulding-
injecting
softened plastic
into
mould
(can make
complicated shapes
)
High Impact Polystyrene
(
HIPS
)
flexible
,
lightweight
,
impact resistant
,
easily moldable
,
gloss
finished
Not very
recyclable
Example:
expanded foam polystyrene
(protect product packaging)
Suitable for
food containers
(
SELF FINISHING
)
Acrylic
(
polymethyl-methacrylate
)-
Versatile
and
tough
Scratches
and
easily
and become
brittle
if
thin
Acrylic fibres
in
clothing
Seen in
sportswear
,
swimwear
Good
insulator
Negative:
not
recyclable
Polyester
resin- viscous, clear polyester solution
Hardened
resin is tough and
high
abrasion resistance
Suitable for
embedding
objects (jewellery making)
Resin
replicas (anatomical models)
Composite adhesive-
polyester resin used in composite materials
Lightweight
and
waterproof
release agent
is used for non stick purposes
Used to adhere layers
fibreglass
Used in making
boats
,
vehicle parts
Urea formaldehyde
(UF)- good electrical insulator
Paper industry:
improve
tear strength
Timber industry:
UFresin
to bind particles
Promote
easy
care and
anti
wrinkle properties in fabrics
Plastic properties-
Self
finishing
Tough
(impact resistant)
electrical
,
thermal insulator
Electrical insulator-
prevent short circuit and ensure safety
Flexible
PVC coating in UF
Thermoset plastics
are used so they won't melt
Biodegradable polymers-
made of plants
Plants are used for
polymers
instead of
food
(specially for
LICs
)
Thermoplastic
Suitable for
takeaway
box, non
toxic
,
high
melting point (able to
injection
mould)