Plastics Flashcards
What are plastics
Plastics are man-made materials
What are the plastics called that are made of natural substances
Synthetic plastics
What is plastic memory
Each time a plastic is reheated it will attempt to return to its original flat shape unless it has been over heated or damaged. This is called a plastic memory.
What are the two main types of plastic
They’re thermoplastics and thermosetting plastics
What are thermoplastics
Thermoplastics are made up of lines of molecules with few cross linkages. This allows them to soften when heated and to be bent into a variety of shapes and forms. They become stiff and solid again when cold. This process can be repeated many times.
They are suitable for Injection moulding, Vacuum forming, Blow moulding.
What is acrylic plastic
This is the most common plastic in a school workshop. It is purchased usually in the form of sheets and comes in a range of colours. It can be translucent (e.g. smoked), transparent (clear) or opaque (solid colour). It is resistant to most acids and weather conditions. It is easily machined, cemented and polished. It is a good electrical insulator. It is safe to use with food. Ten times more impact resistance than glass. Splinters easily and scratches easily.
It can be used for light units and illuminated signs, watch and clock glasses, simple lenses, aircraft canopies and windows, car rear light units, skylights, furniture, baths, Perspex sheet.
What is polythene plastic
Polythene can be moulded into almost any form due to its excellent moulding qualities. Used for the production of bottles, bowls, toys, tube etc. It is available in large sheets. There are two types: High density which is rigid and hard and low density which is tough and flexible. Machine parts are generally made from high density polystyrene whilst bottles are made from the low density polystyrene.
What is polyvinyl chloride
It is a tough material which can be purchased as a hard material or alternatively a flexible form. It can be welded or bonded with an adhesive. It has a range of uses including water pipes, raincoats, long play records, coating on electrical wires and many more.
