Where do most synthetic plastics come from?
And what are sometimes used
Crude oil but coal and natural gas is also used
Fill in the blanks:
Plastics are……….materials. Plastics have taken the place of traditional materials like……and…..some plastics are derived from………..substances such as animals,………..and……..but most are………… These are named…………plastics
- man made
- woods
- metals
- Natural
- insects
- plants
- man made
- synthetic
What is the definition of plastic memory
Each time a plastic is reheated it will attempt to return to its original flat shape unless it has been overheated or damaged
What are the two main types of plastic called
Thermoplastics and thermosetting plastics
Tell me about thermoplastics
- made up of lines of molecules with few cross linkages
- ^^^ this allows them to soften when heated and to be bent into a mixture of shapes and forms
- they become stiff and solid again when cold
- this process can be repeated many times
- suitable for injection moulding, vacuum forming, blow moulding
Tell me about acrylic (Perspex)(thermoplastic)
Remember at least 5
- most common plastic in a school workshop
- purchased usually in the form of sheets
- comes in a range of colours
- it can be translucent(eg smoked), transparent (eg clear), or opaque (solid colour)
- resistant to most acids and weather conditions
- easily machined, cemented and polished
- good electrical insulator
- safe with food
- ten times more impact resistant than glass
- splinters and scratches easily
- can be used for light units, illuminated signs, watch and clock glasses, simple lenses
Tell me about polythene (thermoplastic)
Remember 5
- can be mounded into almost any shape or form due to its excellent moulding qualities
- used for the production of bottles, bowls, toys, tube etc
- available in large sheets
- there are two types; high density which is rigid and hard or low density which is tough and flexible
- machine parts are normally made from high density polystyrene whilst bottles are made from low density polystyrene
Tell me about polyvinyl chloride (pvc)(thermoplastic)
- is a tough material
- can be purchased as a hard material or alternatively a flexible form
- can be welded or bonded with an adhesive
- has a range of uses including; water pipes, raincoats,long play records etc
Tell me about thermosetting plastics
- made up of lines of molecules which are heavily cross linked
- it creates a rigid molecular structure
- can be heated the first time and shaped but then they become permanently stiff and solid
- they cannot be reshaped
- ideal for saucepan handles, kettle handles, plugs
Tell me about adhesives (glues) (thermosetting plastics)
A good example is ‘araldite’ which is an epoxy resin that hardens when a second chemical is added (a catalyst). It will bond most materials including woods and metals as well as some plastics
Tell me about polyurethane
Thermosetting plastics
-forms the basics of many paints and varnishes because it is very tough and has water resistant qualities
Tell me about melamine formaldehyde
Thermosetting plastics
- used in the production of plastic laminates because of its smooth service and hygienic qualities
- also used in electrical plugs and sockets because it can be cast and it is an excellent insulator
Tell me about polyester resins
Thermosetting plastics
-if resins are combined with a material such as fibre glass the result is a very tough material that can resist impact. This thpe of material is known as a glass reinforced plastic (GRP) and is used in; car body repairs, sailing boats, corrugated sheet because of its lightness, toughness and resistance to water
