plastics and polymers Flashcards
list 4 polymers
nylon, polyethylene, polyester, Teflon
what are mechanical properties
mechanical properties are the characteristics a material displays when subject to an external force
list 4 mechanical properties
toughness
flexibility
elasticity
mouldability
what is toughness
a polymers ability to absorb energy and deform plastically without cracking by dissipating it.
e.g bike helmets
what is elasticity
is a materials resistance to distortion and the ability to return to its original shape
e.g balloons
what is flexibility and folding
the ability of a material to be bent or folded without breaking whilst stiffness is a measure of how rigid the material is.
mouldability
a polymers ability to be shaped into a form or mould will dictate the type of product it is used for.
what two examples of moulding plastics
thermoplastics and thermosets
what is the difference between thermoplastics and thermosets
thermoplastics are usually moulded in a hot or molten state under mechanical pressure.
thermosets are usually moulded in could liquid form and cured using a catalyst.
what are 7 physical properties
Insulation
Self finishing
UV resistant
Melting points
Transparency and translucency
Resistance to chemicals and liquids
Ability to be combined with other polymers and additives
what is the purpose of additives
additives are sometimes used to make polymers easier and more efficient to process
what are class the two types of polymers
thermosets and thermoplastics
what are synthetic polymers
synthetic polymers are produced from finite recourses such as coal, gas and oil
what are natural polymers
natural polymers come from a variety of sources such as rubber and amber, which both come from trees
what is the process of getting synthetic polymers
fractional distillation (different polymers are from different fuels)
what is polymerisation (4 marks)
-molecules of single compounds known as monomers join together
-these atoms join end to end to form long chains
- the long chains of molecules are called polymers
why cant we use large hydrocarbon molecules for polymers
large molecules do not flow very well and aren’t suitable to be made into plastics
what happens in cracking with polymers
breaks down large polymers down into smaller more useful ones
describe the structure of thermoplastics
-have long chains of molecules, tangled together with no fixed structure of pattern
-generally soft and flexible with some shape memory
what is LDPE
low density polyethylene, quite flexible but also tough and is chemical resistant
e.g squeezy bottles or snap lids
what is HDPE
high density polyethene, is tough and has higher strength to weight ratio than LDPE and ahs good chemical resistance
e.g rigid plastic toys or buckets
what is PP
polypropylene is a tough, flexible polymer with excellent fatigue resistance and resistant to chemicals and solvents
e.g medical equipment or moulded furniture
what is HIPS
high impact polystyrene is a rigid lightweight polymer with high impact strength and ability to retain heat
e.g yoghurt pots or plastic cutlery
what is ABS
acrylonitrile butadiene styrene is a hard and tough with excellent impact strength and chemical resistance
e.g builders helmets or car bumpers
what is PMMA
polymethyl methacrylate is a lightweight tough material relatively poor chemical resistance compared to other polymers
e.g baths or lenses in glasses
what is nylon
nylon is the first commercially successful thermoplastic polymer it is durable and resistant to abrasion
e.g tents or seat belts
what is rigid PVC
polyvinyl chloride is one of the most widely used polymers and can be both rigid and flexible it has good chemical and weather resistance
e.g plumbing or external doors
what is flexible PVC
plasticisers are added to PVC to increase flexibility it is water and chemical resistant
e.g inflatable products or alternative leather
describe thermosets
thermosets are more brittle than thermoplastics and are best suited to stiffer mouldings , cant be reheated or reshaped
what are stock forms
the standard shapes and sizes in which a material is available
list 6 stock forms
- sheet
- film
- granules
- rod and other extruded forms
- foam
- powder
what are elastomers
elastomers are polymers that are highly elastics and capable of recovering their original shape after being stretched most elastomers are thermosets
name some examples of elastomers
thermoplastic elastomers
stretching elastomer
grip based elastomers
texture based elastomers
what is vulcanisation
vulcanisation is a process used to cure rubber making it harder, more durable and heat resistant
