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:warning: PLASTICS:Plastics are materials…
:warning: PLASTICS:Plastics are materials formed by polymers. The polymers in plastics are
made from long chains of carbon atoms. :warning:
Natural plastics are obtained directly from raw vegetable matenals
— for example, cellulose or latex, or from animal proteins.
Synthetics plastics are made from compounds extracted from petroleum natural gas and carbon. The maionity of plastics belong to this group.
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THERMOSTABLE PLASTICS
These plastics are made from compounds dertved from petroleum They are formed by strongly-linked
chams runmng in different directions
When heated, they become soft and can be shaped.
When cooled , they cannot be remoulded by appliying heat
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Elastomers
Made by vulcanisationi mixing sulphur and rubber, and heating to 160º They are hard, resistant and very elastic — stretching easily under
force.
They' re formed by chains linked laterally and then folded over
themselves, like a ball of wool or strtng
Formation techniques
When we manufacture plasttc obiects ln Industry, the plastic Is avialable In three different forms, powder, granules and resins.
. Extrusion
- We put thermoplastic, in granular form, Into a previously heated cylinder
- We apply pressure by means of a large, rotattng screw, whtch forces
the melted matenal out, through a nuzzle.
- We cool the shaped material slowly In a refngerated water bath until
lt's solid.
- Finally, we collect the pieces of plastic through a feeder system.
. Lamination
Thermoplastic produced by the extrusion method ls passed through a
senes of hot cylinders to produce sheets of varying thtckness.
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Joining plastics
When plastics have been formed, shaped and finished, we can join
pieces to each other
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