PLASTICS
What are plastics?
Plastics are materials formed by polymers. The polymers in plastics are made from long chains of carbon atoms.
What do we use them for?
They are used for making containers and packaging. We also use plastics in many economic and industrial sectors.
Examples: Plastic bottles, shampoo bottles.
We use plastics, for example in telecommunications, transport, construction, medicine, agriculture, and information technology.
Origin and transformation of plastics
We can describe plastics as:
Natural plastics obtained directly from raw vegetable materials like latex or cellulose.
Synthetic plastics are made from compounds extracted from petroleum, natural gas and carbon. The majority of plastics belong to this group.
The transformation of these raw materials and compounds into plastics is called polymerisation.
Properties of plastics
Strength, elasticity, rigidity and flexivility
Other properties
Mechanical, acoustic, electrical and thermal.
Ecological properties
There are three recycling processes;
Mechanical recycling
Energetic recycling
Chemical recycling
Agglutination
Extrusion
Floating
Pelletising
Separation and crushing
Classification of plastics
Thermostable plastics
Elastomers
Thermoplastics
We manufacture thermoplastics from compounds acquired from petroleum.
These plastics are made from compounds dertved from petroleum.They are formed by strongly-linked chams runmng in different directions.
Made by vulcanisation mixing sulphur and rubber, and heating to 160'C.
Formation techniques
Extrusion
Vacuum forming
Lamination
Moulding
Injection moulding
Blow moulding
Used to form: bathtubs, dashboards, shop signs and egg boxes
Used to form: worktops, to cover surfaces of kitchen cupboards and drawers
Used to form; wrapping, lining for electric cables, tubes and pipes.
Shaping and finishing techniques
We can use different tools and machines to finish the plastic objects that we have made.
Principal techniques are cutting, perforating, trimming and filing.
Joining plastic
When plastics have been formed, shaped and finished, we can join pieces to each other.
2 types
Permanent joints
Temporary joints
We use this type of joint when we don't want to separate or dismantle the pieces.
We can join and then separate objects with mechanical fasteners.