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PLASTICS (ecogolical properties (• Mechanical recycling. We make new…
PLASTICS
ecogolical properties
• Chemical recycling. We apply chemical processes to make new
materials from the original components of plastic residues.
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En ergetic recycling. We can incinerate plastics and the energy that
is produced is used tn industry, for heating or producing electnctty.
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Formation techniques
Extrusion
We apply pressure by means of a large, rotattng screw, whtch forces
the melted matenal out, through a nuzzle.
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we put thermostatic, in granular form , into a previusly heated cylender
Finally, we collect the pieces of plastic through a feeder system
Lamination
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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 extract the air below the sheet so that the plastic ts pulled against
the instde walls of the shaped mould, and the desired form ts created
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We leave the mould to cool, then remove the obiec
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Moulding
blow moulding
we put a tubular-shaped piece of plastic into a hollow mould wich has the same shape as the object that we want to make
- We close the mould and blow pressurised air into it, so that the plastics adheres to the sides of mould and take its shape
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
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 malleable
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injection
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When the material has cooled and solidified, we extract it from the mould
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finishing techniques : Principal techniques are cutting, perforating, trimming and filing
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ORIGIN
Natural plastics: are obtained directly from raw vegetable materials
— for example, cellulose or latex, or from animal proteins.
Synthetic Plastics : are made from compounds extracted from petroleum , naturla gas and carbon
The transformation of these raw matenals and compounds into plastics
is called polymerisation.
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Properties of Plastics
Strength, elasticity, rigidity and flexibtflty are charecteristics of many plastics
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• mechanical: malleabrlity, ductility, mechanical resistence
• other properties: low density, impermeability