UNIT 1.3 - POLYMERS Flashcards
THERMOPLASTICS
- A material which can be repeatedly reheated and reshaped
ACRYLIC
Thermoplastic
PROS: tough/hard/good chemical resistance/available in translucent and transparent
CONS: not shatterproof/easily scratched
USES: car light castings/CNC laser cut items/lighting units/lighting covers and baths
LDPE - LOW DENSITY POLYETHENE
Thermoplastic
PROS: very tough/good chemical resistance/weatherproof/available in translucent and transparent
CONS: low level of rigidity/low strength/stress cracking
USES: detergent bottles/toys/carrier bags/bin liners/general packaging/food wrap film/food trays
HDPE - HIGH DENSITY POLYETHENE
Thermoplastic
PROS: available in translucent and transparent/we
atherproof/tough/good chemical resistance
CONS: stress cracking/low strength
USES: chemical drums/toys/household and kitchenware/long life carrier bag/buckets/bowls
PET - POLYETHENE TEREPHTHALATE
Thermoplastic
PROS: available in translucent and transparent form/hard/tough/good chemical resistance
CONS: susceptible to heat degradation - becomes toxic/not biodegradable
USES: single use drinks bottles/food packaging/detergent bottles/shampoo bottles/food trays
PVC - POLYVINYL CHLORIDE
Thermoplastic
PROS: available in translucent and transparent form/hard/tough/good chemical resistance/flexible/good weathering resistance
CONS: poor heat stability/emits toxic fumes if heated/most environmentally damaging plastic
USES: hose pipes/cable insulation/medical grade tubing/inflatable products/imitation leather/seat coverings
uPVC - RIGID POLYVINYL CHLORIDE
Thermoplastic
PROS: rigid/opaque/tough/hard/good weathering resistance/good chemical resistance
CONS: prone to sagging/structurally not very strong
USES: window frames/external doors/guttering and downpipes for buildings/water service pipes/bank cards
PP - POLYPROPELENE
Thermoplastic
PROS: available in translucent and transparent form/tough/good chemical resistance/good fatigue resistance (hinge property)
CONS: susceptible to UV degradation/high flammability/high thermal expansion
USES: rope/folders/folio cases/food containers/medical equipment
ABS - ACRYLONITE BUTADIENE STYRENE
Thermoplastic
PROS: tough/hard/available in opaque
CONS: poor fatigue resistance/poor uv resistance
USES: telephone handsets/rigid luggage/domestic appliance housings/handles/computer housings/remote control casings/calculator casings
THERMOSETTING PLASTICS
- When heated undergoes a chemical change whereby the molecules form rigid cross links
- Cannot be reheated and reshaped, even a very high temperatures
EPOXY RESIN
Thermosetting
PROS: rigid/clear/hard/tough/chemically resistant
CONS: strong toxic fumes/high cost/long curing time
USES: adhesives/surface coatings/encapsulation of electrical components/cardiac pacemakers/aerospace applications
UF - UREA FORMALDEHYDE
Thermosetting
PROS: hard/heat resistant/good electrical insulator
CONS: brittle/lack of moisture resistance
USES: electrical fittings/adhesives
PR - POLYESTER RESIN
Thermosetting
PROS: rigid/heat resistant/chemically resistant
CONS: brittle/strong odour/toxic fumes
USES: castings/used in layup process for GRP for boat hulls/car parts/chair seats
ELASTOMERS
- Materials that at room temperature can be deformed under pressure and then upon release of the pressure, will return to their original shape
NATURAL RUBBER - POLYISOPRENE
Elastomer
PROS: high tensile strength/good hardness/tough/electrical insulator/good cold resistance
CONS: not ductility (low elongation)/affected by temperature/expensive/
USES: automotive industry such as tyres/tubes/hoses/gaskets/belts/balloons/toys/footwear
