Almost all plastics in use are thermoplastic, meaning when heated they will liquefy and be capable of taking a new form. Once a plastic polymer has been grown in a chemical factory, it may be chopped into pellets. The pieces are melted down and injected into a mould to create plastic parts, anything from intricate gears, to water bottles. This process is called injection moulding. Plastics are by far the best candidate material to be used in such a manufacturing process.
- Skill level:
Things you need
- Scrap plastic (anything from polythene to plastic water bottles)
- Metal can (emptied soup can will work)
- Oven (capable of 122,354 degrees C)
- Aluminium foil
Cut scrap water bottles into about one-inch square fragments. Scissors will cut though the bottle, however the bottle cap and threaded bottle opening may be thicker and stronger. These parts may be discarded.
Gather the shredded scrap plastic pieces into the metal can and fill halfway. Remove the can's label.
Cover the opening of the metal can with aluminium foil to prevent the plastic from oxidising in the presence of air.
Place the finished can assembly into an oven set to 220 to 270 degree. Polythene usually melts over this range, depending on the exact polymerisation geometry of the ethylene molecules.
Melt the plastic. This process may take a few hours depending on the mass of the plastic to be melted. Do not use excessive heat, which would damage the plastic. When the plastic liquefies, it will take the shape of its container, which is the shape of the can in this case.
Turn off the oven. Allowing the experiment time to cool gradually will allow the molecules of polythene to crystallise. As a result, the plastic will appear white and opaque. If the molten plastic is cooled rapidly, the plastic will be frozen into a "glassy" transparent state.
Turn the can upside down. Pry out the solidified and cooled plastic. The can might need to be cut apart to release the plastic. In this case, use sheet metal cutters and wear gloves.
Tips and warnings
- The difference between the bottle cap's white colour and the bottle's clear appearance is determined entirely by the rate at which the original molten plastic was cooled.
- Some plastics may release harmful, poisonous gas when burnt. PVC for example, may release chlorine compounds when burnt. Try to melt plastics without burning them. Use adequate ventilation for safety.
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