Large scale production processes
Since A polymer is a large molecule formed from many identical smaller molecules (monomers). Polymers can be natural or synthetic. Plastics are long chains of polymers. have a relatively low melting point, they can be shaped easily once A term used to describe a liquid substance (eg rock, glass or metal) formed by heating a solid. by either Molten material forced into a mould. or A material is pushed through a die so that the cross section remains the same for the length of the material..
Injection moulding
Injection moulding is used in industry to produce most When the same product is manufactured many times. polymer parts using the following process:
- granular plastic is held in a hopper
- it is moved via an A spiral rotating in a tube to push material in one direction. along a heated tube, called the heating chamber
- once the polymer has been melted, it is pushed into a mould with a A pump operated by the displacement of water (in some cases oil) that is used to give unidirectional force. - the use of the hydraulic ram ensures just enough material is injected into the mould each time
- the mould is then cooled so that the moulded plastic can be removed
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Extrusion
Extrusion works in a very similar way to injection moulding:
- granular plastic is held in a hopper
- it is moved by Archimedean screw along a heated tube, called the heating chamber
- once the polymer has been melted it is pushed through a die mould, which will form the shape of the extrusion
- because there is no hydraulic ram in this process, molten plastic can be fed through the die continuously
Common extruded polymer products are plastic pipes, tubes and guttering.
