What is a thermoplastic?
Its a plastic that can be re-shaped by heating it.
What is a thermosetting plastic?
Its a plastic that cannot be re-shaped by heating.
What material are majority of are plastics, and what does that mean?
They are all mainly synthetics and this means they are man-made chemical process.
Name 2 types of thermoplastics and their properties:
PET- usually in transparent form, used for bottles and food containers.
HDPE- strong and stiff with excellent chemical resistance, used for bowls, buckets and pipes.
Name 2 types of thermosetting plastics and their properties:
Polyester resin- hard, brittle, strengthened by laminating it with fibre glass. Used for boat hulls, garden furniture, car bodies.
Urea Formaldehyde- tough, attractive, good heat insulator. Used for electrical fittings, waterproof glue.
What are the main facts about injection moulding?
- Not identical cross section
- very common
- electrical goods
- put granules in hopper, pushed in chamber by rams, bands soften into liquid under pressure then put in mould, then is cooled.
What are the main facts about extrusion moulding?
- has uniformed cross section
- granules/powder are put in hopper through a heated cylinder, die fitted to end of extruder shapes the plastic, cooled as it leaves the die
What are the main facts about blow moulding?
- shapes with one open end-hollow
- warm condensed air is forced against the softened sheets causing it to expand in a mould or dome.
What methods are used to change the shape of manufactured boards?
- line bender
- vacuum forming
- extrusion/injection moulding
What are the main facts about line bending?
- radiant heat from electric element
- enclosed in channel
- acrylic laid across support opening turnover every so often
What are the main facts about vacuum forming?
-make mould>put on tray>lower tray>put plastic on top of chamber>heat>make sure its malleable>remove heater>raise tray into plastic>switch on vacuum(remove air)>blow air back in>clean edges!!
What is glass reinforced polyester(GRP)?
Its layers of fibre matting are placed over a former, and a liquid resin is poured over. The resin hardens to produce a rigid material. Further layers can be added. GPR is used for larger and more complex shaped, such as boots.
What are advantages and disadvantages of GRP?
ads - double strong, resistant to all weather, oil and water, easy to form and very cheap
disads- fibre glass fumes/particles are hazardous and you must wear protective gear.
Name 3 types of glues:
- contact adhesive
- epoxy resin
- hot glue stick
What is the dry time, material uses on and uses and a type of this glue of contact adhesive?
- used on wood, metal, plastics
- dry time = instant
- waterproof, med strength, good for plastic laminates
- left to touch dry then pressed together.
What is a brand of contact adhesive glue?
evostick
What is the dry time, material uses on and uses and a type of this glue of epoxy resin?
- used on wood, plastics, metal
- 1/2 - 6 hours
- waterproof, strong joint
- 2 tubes = resin + hardener, mixed together applied and then need to be held when drying
What is the dry time, material uses on and uses and a type of this glue of hot glue stick?
- used on wood, metal, plastics
- dried on cooling
- waterproof, weak, only suitable for modelling temporary things
- comes in a stick form
What is a brand of epoxy resin?
aridite