Materials - plastics Flashcards
What is a thermosetting polymer?
A polymer which becomes irreversibly hardened upon being cured.
What is curing caused by?
The action of heat or suitable radiation and may be promoted by high pressure or the use of a catalyst.
What is the main difference between thermoforming and thermosetting plastics?
Thermoplastics can generally be re-melted and reshaped whereas thermosets cannot.
What are the advantages of thermosets over thermoplastics?
Usually tougher due to cross links
Usually stronger and harder
Often higher heat resistance
Disadvantages of thermosets over thermoplastics.
Cannot be reformed into other shapes
When heated they will burn
Difficult to recycle
Advantages of kevlar
Strong tensile strength and flexible as molecules can pack closely together.
Tough
Disadvantages of kevlar
Not waterproof by itself
Degrades in sunlight
Advantages of acrylic
strong tensile strength
impact resistant and when it breaks it doesn’t shatter like glass
lightweight
come in a variety of colours
durable
Disadvantages of acrylic
not very hard/scratchproof
low heat resistance
Where is acrylic generally used?
lenses, acrylic nails, and paint to medical devices, furniture, and LCD screens.
Advantages of epoxy resin?
has adhesive properties
chemical resistant
moisture resistant
Disadvantages of epoxy resin
Health hazard
common effects of overexposure to the chemicals used in epoxy resin systems are eye, nose, throat, and skin irritation, skin allergies, and asthma
Where is epoxy resin most commonly used?
electrical components
high tensile electrical insulators
fibre-reinforced plastic materials
Advantages of PTFE (Teflon)
non-stick properties
heat resistance
corrosion resistance
high electrical resistance
non flammable
low friction
inert
durable
Disadvantages of Teflon.
Releases toxic fumes when heated at high temperatures
Can peel and scratch over time causing it to lose its non stick properties
Where is Teflon most commonly used?
In making non-stick cookware
Making waterproof fabric
Advantages of Nylon (polyamide)
lightweight
elastic properties
resists damage from oils and chemicals
abrasion resistant
Disadvantages of nylon.
poor resistance to sunlight
low absorbency
heat sensitive
Where is nylon most commonly used?
clothing - tights
rope
parachutes
Advantages of cellophane
Biodegrades in landfill
Can be waterproof and breathable at same time
Disadvantages of cellophane
Poor performance at low temperatures
Cost
Where is cellophane most commonly used?
Food packaging, Sellotape, sweet packaging
Advantages of PVC
Good chemical resistance
Weather resistant
Stiff
Tough
Hard
Lightweight
Disadvantages of PVC
Can become brittle over time
Ultraviolet light causes the brittleness
