Unit about Plastics for 3º ESO (Bilingual Section)

1. PLASTICS

2. PLASTICS AS A CONCEPT:
Plastics are Polymers Of Organic Compounds Or Resins that
can be moulded Into any shape by the application of heat and
pressure.
Polymers are produced by the conversion of natural products
by synthesis from primary chemicals coming from oil, gas or
coal.

3. CHARACTERISTICS OF PLASTICS
* They are relatively cheap.
* Most plastics are synthetics and are made from oil.
* Plastics are good insulators which makes them safe to use for
casing electrical equipment and for the covering on wires.
* They are waterproof.
* They are light.
* Most plastics can be made in different colours or can be clear.
* Plastics are non-corrosive and non-toxic (Does not rust or rot)
* Chemical Resistant
* They wash well
* Lower density than Metal
* Moldable
* They are not biodegradable and cannot be easily recycled.

4. MATERIALS PROPERTIES
Materials behave in different ways under different conditions. These types
of behaviour are called material properties.
Conductivity
The ability of a material to conduct heat or electrical energy.
Strength
The ability of a material to withstand a force without breaking or bending.
Elasticity
The ability of a material to bend and then to return to its origin shape and size.
Plasticity
The ability of a material to permanently change in shape.
Malleability
The ability of a material to permanently deform in all directions without cracking
Ductility
is the ability of a material to deform, usually by stretching along its length.

5. MATERIALS PROPERTIES II
Hardness
is the ability of a material to resist wear, scratching and indentation.
Softness
is the opposite property to hardness. Soft materials may be easily shaped by filing, drilling
or machining in a lathe, milling machine or shaping machine.
Toughness
is the ability of a material to withstand blows or sudden shocks without breaking.
Durability
is the ability of a material to withstand wear, especially as a result of weathering.
Fusibility
is the ability of a material to change into a liquid or molten state when heated to its
melting point.
Brittleness
refers to the material’s behaviour when fractures occur with little or no deformation. Glass
is a classic example of a material with this property
Stiffness
is the ability to withstand bending.
Flexibility
refers to metals which remain bent after a bending force has been removed

6. Plastic Composition: Molecular Structure
Monomers : Are the repeating structural unit, and are typically hydrocarbons.
Polymers : Are a chain of either a single type of monomer or several types
arranged in a repeating pattern.
Polymerization: Is a chemical reaction in which two or more monomers
combine to form a polymer of repeating structural units.
Watch this video; POLYMERIZATION

7. TYPES OF PLASTICS
Thermoplastics Or Thermoplast
Plastic material that can be soften when heated with Pressure and can
be remodeled into another shape.
Thermosetting Plastics or Thermoset
Have the property of becoming permanently hard and rigid when
heated or cured. It cannot be softened or remoulded.
Elastomers
An elastomer is a polymer with the property of elasticity. Elastomers or
rubbers are plastics that are composed of long twisted molecules
which stretch and recoil like a spring.

8. THERMOPLASTICS

9. THERMOPLASTICS

10. Pulse para añadir un títuloPulse para añadir un títuloPulse para añadir un títuloPulse para añadir un título
Thermosetting Plastics

11. Thermosetting Plastics

12. ELASTOMERS

13. ELASTOMERS

14. TECHNIQUES AND TOOLS TO WORK WITH PLASTICS
Plastics are obtained through different techniques, in various
forms like a tubes, plates, sheets, profiles etc. Sometimes is
necessary mechanize.
The principal techniques are:
CUTTING
PERFORATING
TRIMMING AND FILLING
JOINING PLASTICS

15. CUTTING
Cutter
To cut Sheets of different thickness. 3-4 mm in PVC up several
centimeters in Porexpan ( Polystyrene. PS)
Scissors
To cut soft thin flexible sheets. * Watch this video:
http://youtu.be/O-FLC9c9rUg

16. CUTTING
Fretsaw
To cut the same way others materials like Wood or Metal, you
can make straight, slating and curved cuts
Jig Saw
to cut pipes, plates and profiles and very large sheets
of plastic, rigid plastics in general. Can make straight,
slating and curved cuts
* Watch this video:
http://youtu.be/nh62xaTEmxw

17. CUTTING
Power press
To cut flat sheets of low density plastic. Makes
simple objects by applying pressure.
* Watch this video: http://youtu.be/r7ZqgqQiExE
Hot metal thread trimmer
To cut sheets of soft thermoplastic

18. PERFORATING
To make holes in plastics, we use to a Drill and a
drill bit. The Drill is a machine tool, it has a drill
bit into the head of the machine that revolves at
high speed for cutting holes.
* Watch video: http://youtu.be/aPoNDd2yTuM

19. TRIMMING AND FILLING
FILE
A File has a rough surface. It’s used to finish surfaces and
edges of hard materials
RASP
A Rasp has an even rogher surface, covered with “”teeth. It’s
used to finish surfaces and edges of soft materials
* Watch this video: http://youtu.be/Bg6K1Ijjahc

20. JOINING PLASTICS
When the plastics are ready, after mechanize (Cutting,
Perforating and Trimming and Filling), we have to join
pieces to each other.
The joins can be:
PERMANENT (FIXED)
OR TEMPORARY (REMOVABLE)

21. TEMPORARY (REMOVABLE) JOINTS
We can join and then seperate objects with mechanical fasteners:
Nut and Bolt
Used to fasten two objects together. Nut used to tighten the bolt
Standard screw
Used to fasten two objects. Holes must be drilled first before the
screw is inserted

22. TEMPORARY (REMOVABLE) JOINTS
DOUBLE ENDED SCREW
Each end of the screw can be inserted into one of
a pair objects

23. FIXED JOINTS
We used this type of joint when its no necessary remove
or separate the pieces.
We can use: Adhesives, Staples and soldering
ADHESIVES: Adhesives are presented in many different
ways:
Resins with two components (waterproof)
Acrylic cement. Used mainly with PVC and Polysterene
Contact adhesives: liquid, work instantly after applying to both
surfaces, used with all types of plastics.

24. STAPLING MACHINE
Stapling is a bonding process fast and simple. Allows joining
plastic to other materials, if they are not very hard. The stapling
machine can be manual or electric.
SOLDERING
We can join thermoplastics using heat and pressure

25. CRÉDITOS
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