Year 10 Manufacturing (Resistant
Lesson 4 Week 4 (Clock Project)
|Plastic properties and uses of common Thermoplastics and Thermosetting Plastics.
Plastics are man-made materials. Plastics have taken the place of traditional materials like woods and metals.
Plastics differ from other materials largely because of the size of their molecules. Most materials have molecules made up of less than 300 atoms, plastics contain thousands of atoms. We call them Macromolecules.
Some plastics are derived from natural substances such as animals, insects and plants but most are man-made. These are named Synthetic Plastics.
Most synthetic plastics come from crude oil but coal and natural gas is also used.
When crude oil is refined gasses are given off . The gasses are broken down into Monomers. These are chemical substances consisting of a single molecule. Thousands of these are linked together in a process called Polymerisation to form new compounds called Polymers.
|There are two main types of plastics and these are named Thermoplastics and Thermosetting Plastics.
|Thermoplastics are made up of lines of molecules with few cross linkages. This allows them to soften when heated and to be bent into a variety of shapes and forms. They become stiff and solid again when cold. This process can be repeated many times.
|Thermosetting Plastics are made up of lines of molecules which are heavily cross linked. It creates a rigid molecular structure. They may be heated the first time and shaped but they become permanently stiff and solid. They cannot be reshaped again.
|Plastic Memory. Each time a plastic is reheated it will attempt to return to its original flat shape unless it has been over heated or damaged. This is called a plastic memory.
|Examine the Common Thermoplastics and Thermosetting Plastics Table.
The table displays a variety of common plastics. It explains where and why each plastic is used. It also explains the properties of plastics and provides information on the common forms of each one.
Using the above table answer the questions below.
|1. Which type of plastic would be suitable to manufacture washing up liquid bottles from?
2. Give two reasons as to why acrylic is used to make external signs?
3. Name a suitable plastic used to transport medical supplies on board ships?
4. A manufacturer of intends to sell mechanical miniature children's cars. It has decided to make part of the gearing system from plastics. Which tough plastic with a good bearing surface would you recommend?
5. Give two reasons as to why guttering and drainpipes are made from Rigid PVC?
6. Name one property of acrylic that may prove to be a disadvantage?
7. The handles of mild steel screwdrivers made in the school workshop need to be protected through the process of dip coating. Which plastic could be used? The same plastic is used to insulate electrical wires.
8. Name a suitable plastic used in the boat industry to make small rowing boats?
9. Which transparent plastic is used to make the windows of garden sheds? Explain why you think it is preferred to glass?
10. Gear systems need to be self lubricating, resistant to oil and have good fatigue resistance. Name a suitable plastic?
To be able to appreciate the great variety of plastics commonly used in society.
To be able to answer questions regarding the properties, uses and common forms of plastics.
|Programmes of study
5b How materials can be combined and processed to create more useful properties, and how these properties are utilised in industrial contexts;