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Plastics (Propeties (Ecological Properties (Mechanical (Separation and…
Plastics
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Formation techniques
Extrusion
- We put thermoplastic, in granular form, Into a previously heated cylinder. 2. We apply pressure by means of a large, rotating screw, which forces
the melted matenal out, through a nuzzle. 3. We cool the shaped material slowly In a refrigerated water bath until lt's solid 4. 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
With this technique, we can produce different finishes, for example glossy, matt or textured. This depends on the outer coating applied by the
final cylinder.
Vacuum forming
We use plastic sheets with a large surface for this technique 1. We put thermoplastic into a mould. 2. We then use a heater to heat the mould and soften the plastic 3. We extract the air below the sheet so that the plastic is pulled against
the instde walls of the shaped mould, and the desired form is created 4. We leave the mould to cool, then remove the object.
Molding
Injection
- We inject melted thermoplastic into a mould 2. When the material has cooled and solidified, we extract it from the
mould.
Blow moulding
- We put a tubular-shaped piece of plastic into a hollow mould which has the same shape as the object that we want to make. 2. We close the mould and blow pressurised air into it, so that the plastic adheres to the sides of the mould and takes its shape. 3. When the object is cold, we remove it from the mould.
Compression.
- We put thermostable plastic, which can be in granular form, into the base of a cavity mould. 2. The outer part of the cavity
mould, shaped the same, is closed to compress the material
inside We then heat it and it becomes soft and maleable 3. The plastic adapts to the shape of the cavity between the two parts of
the mould 4. We extract the object when the plastic has cooled and solidified
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Classification
Thermoplastics
We manufacture thermoplastics from compounds acquired from petroleum.
They' re made up of weakly formed molecular chains.
When we heat them, they become soft, which allows them to be formed into different shapes.
The heating and cooling process
can be repeated many times.
Thermostable plastics
These plastics are made from compounds derived from petroleum.
They are formed by strongly-linked chams running in different directions.
When heated, they become soft and can be shaped.
When cooled, they cannot be remoulded by applying heat.
Elastomers
Made by vulcanisationi mixing sulphur and rubber, and heating to 160ºC.
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 string.
Depending on their origin, plastics can be:
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What are plastics?
Plastics play a big part In our daily lives.
Plastics are materials formed by polymers. The polymers in plastics are made from long chains of carbon atoms.
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