KEY CONCEPTS OF PLASTICS AND TEXTILES

-  Both natural and synthetic fibres can be woven to make a variety of textiles.

- Natural fibres may come from animal sources (wool, silk), plant sources (cotton, linen, esparto, bamboo) and mineral sources (gold, silver and copper fibres).

- Synthetic fibres, such as nylon, polyester, rayon and Lycra, are plastic materials.

(LYCRA)

KEY CONCEPTS OF PLASTICS AND TEXTILES

- Modification techniques use tools and machines to make changes to prefabricated materials, such as sheets, bars or mouldings.
- Examples of these techniques include: measuring - drawing marks and lines - cutting - drilling - filing and sanding - joining.

-  You must always pay special attention to health and safety rules.

KEY CONCEPTS OF PLASTICS AND TEXTILES

- Various industrial techniques can be used to manufacture plastic products, such as: extrusion, calendering, vacuum forming and moulding.

- The main techniques for using moulds are as follows: blow moulding, injection moulding and compression moulding.

(BLOW MOULDING)

KEY CONCEPTS OF PLASTICS AND TEXTILES

-Thermoplastics are usually made from petroleum products. The most common thermoplastics are:

 • Polyethylene terephthalate (PET).

 • High-density polyethylene. 

 • Polyvinyl chloride (PVC). 

 • Low-density polyethylene. 

 • Polypropylene.

 • Moulded polystyrene. 

 • Expanded polystyrene or Styrofoam.

(PET)         

- Thermosetting plastics are made from petroleum products. They include: 

• Polyurethane.

• Bakelite. 

• Melamine. 

• Polyester resins.

(MELAMINE)

- Typical elastomers include rubber and neoprene.

KEY CONCEPTS OF PLASTICS AND TEXTILES

- Plastics consist of long chains of atoms which are mostly composed of carbon.










- Plastics be classified into natural and synthetic plastics.

- The process of manufacturing plastic is called polymerisation.

- Plastic materials are resistant, insulating (against electricity, heat and sound), ductile, malleable, impermeable and light.

- There are three types of plastic recycling processes: chemical and mechanical recycling and energy recovery.

BASIC DEVICES MADE WITH ELECTRONIC COMPONENTS

We can build various devices with the electronic components discussed in the previous section. Here are two examples:
Timers.
 A timer is a device thet operates for a certain period of time and then shuts itself off automatically.

Integrated circuits.
Integrated circuits consist of miniature electronic components, such as transistors, resistors and capacitors.

ELECTRONIC COMPONENTS

Transistors.
They are made from semiconductor materials and have three electrodes called the base, the collector and the emitter.
There are two types of transistor: NPN and PNP.

-When no electrons are flowing through the base, then no electrons can pass from the collector to the emitter. The transistor is in cut off.

- When many electrons are flowing through the base, the route between the collector and the emitter will be completely open. The transistor is in saturation.

- When the flow of electrons through the base is between the cut off and saturation levels, it will be proportional to the flow of electrons between the collector and the emitter. The transistor is in the active region.

ELECTRONIC COMPONENTS

Capacitors.
Capacitors are components that can store an electrical charge.
The value of a capacitor indicates the charge in volts that it can store. This is measured in farads (F).

Diodes.
A diode is an electronic component made from semiconductor materials. It only allows electric current to flow in one direction.
A diode has two electrodes: an anode (A) and a cathode (K)
A LED only gives off light when an electric current flows through it.

ELECTRONIC COMPONENTS

Resistance that depends on a physical factor.
- Resistance that depends on temperature is called a thermistor.
There are two types of thermistors:
- Negative temperature coefficient (NTC): The resistance decreases as the temperature rises.                        
                                                   

-Positive temperature coefficient (PTC): The resistance increases as the temperature rises.

LDR: Resistance that varies according to the amount of light received. The resistance decreases as the amount of light increases.

ELECTRONIC COMPONENTS

 Fixed resistance or resistor
A fixed resistance or resistor opposes the flow of electric currents. 
Its value, which we measure in ohms, is indicated by a code of colours and numbers.
The first two stripes are replaced by two numbers, according to their colour. The third stripe indicates the number of zeroes that we must add to the previous figure. The fourth stripe indicates the tolerance or the maximum deviation from the theoretical value.

Variable resistance or potentiometer

The value of a variable resistance or potentiometer can be adjusted between zero and the maximum value specified by the manufacturer.

 

RESISTANCE

 POTENTIOMETER.

                                

ELECTRONICS

Electronics involves the study of circuits and components that modify the intensity, direction or properties of electric currents.

LIMIT SWITCHES

The battery provides power for the pump, which moves water from the lower tank to the upper tank. 
Whe the upper tank is full, a limit switch turns off the pump.
The switch is activated when the float rises to a certain level.
When the water level goes down, the switch returns to its original position and the pump turns on again.

CAM SWITCH CONTROLLER

The device on the side of the pulley in the picture above is called a cam. The shape of this device allows us to control the moment and duration of an activity.

ELECTROMAGNETIC CONTROL SYSTEMS

An electromagnetic control system activates the various parts of a machine, at the right moment and for the right amount of time, ensuring that the machine functions properly.

RELAYS

A relay is an electromagnetic component that works as a switch. When electricity passes through the coil, it acts like a magnet. When electricity stops flowing, the moveable contact goes back to its original position.

ELECTRIC MOTORS

An electric motor is a device that can transform electrical energy into movement. It uses the forces of attraction and repulsion between a magnet and an electrically- charged wire.

ELECTROMAGNETIC GENERATORS

There are two types of generators, depending on the type of current that is produced:
-Dynamos: They produce direct current. A dynamo consists of a magnet and a rotary coil. The coil is located between the two poles of the magnet. The ends of the coil have two semi-circular conductors, which form the commutator.

-Alternators: They produce alternating current. They are identical to a dynamo, except for the commutator, which consists of two metallic rings connected to carbon brushes. Instead of direct current, this produces alternating current.

ELECTROMAGNETIC MECHANISMS

Electromagnetic mechanisms are devices that can convert movement into electricity or vice versa. They use electromagnetic phenomena to produce electricity or convert it into mechanical energy.