TEXTILES

5 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)

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

MODIFICATION TECHNIQUES

4 MODIFICATION TECHNIQUES

- Modification techniques use tools and machines to make changes to prefabricated materials, such as sheets, bars or mouldings.

- Examples of thes techniques include: measuring-drawing marks and lines-cutting-drilling-filing and sanding-joining.

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

PLASTIC FORMING TCHNIQUES

3 PLASTIC FORMING TCHNIQUES

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

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

THE CLASSIFICATION OF PLASTIC

2 THE CLASSIFICATION OF PLASTIC.

- Thermoplastics are usually made from petroleun products. The most common thermospastic are:

• Polyethylene terephthalate
• High-density polyethylene
• Polyvinyl chloride
• Low-density polyethylene
• Polpropylene
• Moulded polystyrene
• Expanded polystyrene or Styrofoam

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

• Polyurethane
• Bakelite
• Melamine
• Polyester resins

- Typocal elastomers include rubber and neoprene.

Plastic materials

1.PLASTIC MATERIALS

• Plastics consist of long chains of atoms which are mostly composed of carbon.
  
• Plastic can be classified into natural and synthetic plastic.
  
• The process of manufacturing plastic is called polymerisation
  
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• Plastic materials are resistant, insualting, ductile, malleable, impermeable and light.
• there are three type of plastic recycling processes: chemical and mechanical recycling and energy recovery.

Electronics

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

Electronic components
In this section, we will analyse the most common electronic components.

-Fixed resistance or resistor
A fixed resistance or resistor opposes the flow of electric currents. Its calue, which we measure in ohms, is indicated by code of colour and numbers

Variable resistance or potentiometer

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

Resistance that depend 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 rise.

LDR: Resistance that varies according to the amoint of light received. the resistance decreases as the amount of light increases. These devices, like potentiometers, are often used in security systemns, where they are parts of sensors

Capacitors

A capacitor can store electrical energy from a battery and then use it to power a light bulb until the charge is totally depleted.

Capacitors are components that can store an elctrical 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 cathode (k)

A LED only gives off light when an electric current flows though it.

Electromagnetic control systems

Activates the various parts of a macine, at the right movement and for the right amount of time, ensuring that the machine functions properly.

Cam switch controller

The device on the side of the pulley in the pictures above is called cam. The shape of this device allows us to control the moment and duration of an activity, such as the rinning of a motor or the illumination of a light bulb

Limit switches

The picture below show an electrical control system for a water tank. THe battery provides power for the pump, which moves water from the lower tank to the upper tank. When the upper tank is full a limit switch turns off the pump.

There are two types of limit switch: