2. Take a few minutes to look around the room and identify
some everyday plastics.
Everyday plastics
Chairs
Jumper
Comb
Carrier bag
Pencil case
Polypropene
Acrylic
Nylon
Polyethene
Neoprene
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4. Plastics can be broken down into two categories:
thermoplastics and thermosetttings.
Categories of plastics
Thermoplastics
Soften when heated
Can be reshaped
More commonly used in schools
Thermosettings
Initially set by heat
Cannot be reshaped once set
Extremely strong and durable
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5. Plastics have an extremely wide range of uses. Here are
some common products made from thermoplastics.
Uses of plastics (thermoplastics)
Acrylic
High Density
Polyethene
Polystyrene
ABS
Low Density
PolyethenePolypropene
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6. Thermosets have different qualities to thermoplastics.
Here are some uses for thermosets.
Uses of plastics (thermosets)
Melamine formaldehyde
Urea
formaldehyde
GRP
Phenol
formaldehyde
Epoxy
resin
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8. Properties of plastic
• Light weight
• High toughness
• Feels waxy
• Low thermal conductivity
• Resistance to flow of
current
• A wide range of colours
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13. Working with plastics – industrial processes
Injection moulded
polyethene wheel
The injection moulding process
involves heating plastic granules to
their melting point and then
injecting them at high pressure
through a nozzle into a mould.
When the plastic cools the mould is
opened and the newly formed
plastic part can be removed.
What similarities and differences can you identify
between the vacuum forming and injection moulding
processes?
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14. Materials can be joined temporarily or permanently.
Three methods of joining plastic are shown below.
Joining plastics
Nut, bolt and
washer
Riveting Adhesive
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15. MASTER QUESTIONS?
Which method is permanent?
Which method is most quick?
Which is the strongest method to join plastic?
Which method is most expensive method?
Which is the least expensive method?
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16. Working with plastics – finishing techniques
Plastics have excellent surface qualities. As they are
self-finishing, plastics require little or no surface finish.
However, when designers want a specific colour or texture,
spray paints can be used.
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This is a simple starter activity to get students to focus on plastic products common to them. You may wish to replace the list of products and plastics with suitable examples from the classroom students are in.
This is a simple drag and drop exercise, giving a very general background to the origins of most plastics. Other things to discuss: What forms do plastic come in (granules, powder, sheet)? What shapes does solid plastic come in (tube, bar, square, block)?
The word thermoplastic and thermoset can be explored before revealing the descriptions. For example, Thermo = heat Plastic = bend without breaking/flexible with the application of heat Set = will not move after initial heat is applied. Students could decide on their own definition of a thermoset and thermoplastic and originate ways of remembering their definitions.
Discuss other uses for the thermoplastics mentioned. Why are thermoplastics good plastics for the particular products shown?
Discuss other uses for the thermosets mentioned. Why are thermosets good plastics for the particular products shown?
Detailed information about plastics materials and links to manufacturers can be found at http:/www.bpf.co.uk/bpfindustry/plastics_materials.cfm. The items in the picture are: melamine worksurface, acrylic jumper, polystyrene egg box, polypropene chair and table, acrylic lampshade, PVC shoes, high density polyethene washing up bowl, low density polyethene washing up bottle, ABS kettle, PVC cable, Urea formaldehyde electric socket.
Teaching suggestions: Introduce properties as qualities of plastic. Hand out samples of plastic, either in raw form or as a product. Identify some qualities. How does it feel? How much does it bend? Does it scratch easily? Does light pass through it? Is it brittle? Discussion can focus around an enquiry and lead to establishing correct technical vocabulary for properties of plastic. You may wish to prepare an extended version of the activity above by making a laminated resource to match properties and descriptions.
Images courtesy of Middlesex University Teaching Resources (http://www.mutr.co.uk) This slide can be used to prompt discussion about suitable tools and equipment available in most workshops to cut, manipulate and finish plastic sheet. Discussion could focus around: In which direction do the teeth point on a coping saw? Why is this? What does it tell us about how a coping saw cuts? What implications does it have for our cutting technique? Teeth per inch (TPI) on a hacksaw – why is it beneficial to have more TPI when using plastics? What different types of file are there? What profiles do you have in the workshops? What’s the difference between cross filing and draw filing? What different types of glass paper are there? Why is wet and dry paper particularly useful for this application? What effect will wetting the file and wet and dry paper have on the dust created when filing/smoothing? When would you polish? What is polish – what does it do? What different types of polish could we use? Is there a specific order that these tools/equipment should be used in? What other health and safety precautions should be take when using the tools and equipment above?
You may wish to create your own photographs of equipment and resources that students are likely to encounter in their own workshops. Scroll Saw image courtesy of Hegner (www.hegner.co.uk) Drill image courtesy of Middlesex University Teaching Resources (http://www.mutr.co.uk) Over and hot wire strip heater images courtesy of CR Clarke & Co (www.crclarke.com) Buffer image courtesy of RJH (http://www.rjheng.co.uk/educational.html).
Video courtesy of Formech International Limited (www.formech.com) Links Information about vacuum forming and suggested projects can be found at http://www.formech.com/educational/index.htm. http://www.plastech.org/vacuum.htm also details the vacuum forming process, and data sheets about plastic materials, vacuum forming and injection moulding can be downloaded from http://www.crclarke.co.uk/Pages/English/contact.html.
Images courtesy of CR Clarke & Co (www.crclarke.com). Discussion could focus around: Scales of production and appropriate manufacturing techniques and tools/equipment Similarities between the processes – use of moulds or dies, use of hoppers and the Archimedean screw to feed plastic into mould/die, mainly thermoplastics used in these processes. Justify the differences. Examples of moulds and dies Male and female moulds Release angles Draw depth ratio (relationship between width and depth of a mould).
Images courtesy of Middlesex University Teaching Resources (http://www.mutr.co.uk) and Axminster Power Tool Centre (http://www.axminster.co.uk). Discuss the difference between temporary and permanent methods of joining plastic. Possible questions: Which methods are permanent? Which is the quickest method? Which is the strongest method? Which is the most/least expensive method? What health and safety precaution need to be taken when using these joining methods? What other joining methods could be used to join plastic either temporarily or permanently?
This plenary has been designed to be used as a recapping and extending exercise, based on the knowledge and understanding gained during this module. Follow the guidelines below: Organize two teams: red and yellow Explain that each team is asked a multiple choice question in turn. To provide an answer, you click on your chosen answer. If the answer is correct, then drag the counter to the top of a column in the connect 4 grid. If the answer is incorrect, the opposing team has an opportunity to answer. The aim of the game is to score four counters in any direction: vertically, horizontally or diagonally.
