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AQA GCSE - Design and Technology > 2.7 - Polymers > Flashcards

2.7 - Polymers Flashcards

1
Q

Man-made polymers are referred to as ________.

A

plastics

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2
Q

What are plastics derived from?

A
  • Coal, gas, cellulose and commonly crude oil.
  • Crude oil needs to be processed before use.
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3
Q

What is fractional distillation?

A
  • The process of fractional distillation separates crude oil into useful hydrocarbon products.
  • The different components that are separated out are known as fractions.
  • The fractions include petrol, naptha, kerosene, diesel and bitumen.
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4
Q

In the process of producing plastics, what happens after fractional distillation?

A
  • A chemical called naphtha, a mix of hydrocarbons used for the production of many different plastic polymers, is vented off from the distillery column.
  • This then undergoes a process called cracking so that individual hydrocarbons, called monomers, are produced.
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5
Q

In the process of producing plastics, what happens after the hydrocarbon is cracked?

A
  • Monomers undergo polymerisation, which links monomers together to make a polymer chain.
  • For example, a long chain of ethylene forms polyethylene which is used to make carrier bags, toys and bottles.
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6
Q

Give an example of a common bioplastic.

A
  • The one of the most common plant-based polymers is polylactic acid (PLA).
  • It is commonly used in a 3D printer.
  • PLA is obtained from corn starch - the corn is fermented to produce lactic acid, which is polymerised to produce polylactic acid.
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7
Q

Why is the development and use of bioplastics important?

A

Bioplastics are being continually developed to combat the environmental concerns related to the non-biodegradable properties of plastic polymers.

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8
Q

What are the properties of thermoforming plastics?

A
  • These are easy to mould and shape when hot.
  • They can be formed into complex shapes and reformed multiple times.
  • They are lightweight, strong, waterproof and corrosion resistant.
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9
Q

What are the properties of thermosetting plastics?

A
  • A thermoset is irreversibly hardened and cannot be reformed.
  • It makes a hard, but often brittle plastic which resists deformation.
  • It has good heat and electrical resistance (good insulator) and is commonly used for electrical components, domestic plugs and switches.
  • It also has good chemical resistance and structural integrity. It can be reinforced to produce a strong, durable material.
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10
Q

What are some ways of modifying plastics?

A
  • Stabilisers
  • Pigments
  • Plasticisers
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11
Q

How do stabilisers modify plastics?

A
  • Stabilisers can be added to make plastic more resistant to heat and light.
  • Over time UV light degrades plastic, turning it brittle and faded.
  • This has an impact on strength, and changes the surface appearance and texture.
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12
Q

How do pigments modify plastics?

A

Pigments can be added to vary the colour of plastics.

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13
Q

How do plasticisers modify plastics

A
  • Plasticisers give a material improved flexibility .
  • Are commonly used in PVC to improve applications such as sheathing for electrical cables and car interior trim.
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14
Q

What are some different stock forms that plastics are produced in?

A
  • Film
  • Granules / pellets
  • Foam
  • Rods / tubes
  • Powder
  • Sheet
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15
Q

What is film used for? (Stock form)

A

Used for packaging, bags, labels and sheeting.

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16
Q

What are granules / pellets used for? (Stock form)

A

Used for extrusion and injection moulding.

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17
Q

What is foam used for? (Stock form)

A
  • Can be made flexible or rigid.
  • Used for thermal insulation and packaging.
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18
Q

What are rods / tubes used for? (Stock form)

A
  • Used in electrical, plumbing, garden, military and medical applications.
  • Can be bent to shape.
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19
Q

What is powder used for? (Stock form)

A
  • Mixes well with additives and dyes.
  • Also used in resin glues, spray coating and 3D printing.
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20
Q

What are sheets used for? (Stock form)

A
  • Durable and lightweight.
  • Used for protective surfaces, roofing and signage.
  • Can be cut to size, bent, curved or vacuum formed.
21
Q

Plastic screws, nuts and bolts can be made from PVC, nylon and PET.

What are some useful properties of plastic fittings?

A
  • Resist corrosion and don’t rust, particularly when used in wet or salty conditions.
  • Made to be UV resistant.
  • Flexible, rigid, lightweight and cost effective.
  • Can be reinforced with metal.
  • Non-conductive, so ideal for electrical use.
22
Q

Why are plastic fittings more ideal than metal fittings in some conditions?

A
  • More lightweight
  • More corrosion resistant
  • Non-conductive
  • Cost effective
23
Q

How do plastic hinges differ from metal ones?

A
  • They resist corrosion and are lightweight.
  • Plastic hinges can be reinforced with glass fibre.
  • No lubrication needed due to rust not forming.
  • Also resistant to solvents, sea water and temperature variation.
24
Q

Exam Style Question:
Explain one advantage of using materials that are sold in standard dimensions.
[2]

A
  • Materials are easier to obtain and likely to be stocked by many retailers.

Or

  • Parts are more likely to manufactured in large numbers, making them cost effective due to economies of scale.
25
Q

Describe the process of vacuum forming.

A
  • This technique is used to shape plastic.
  • It works by heating a sheet of plastic, which is then pulled by the vacuum to form around the shape or mould.
  • Once the plastic has cooled and set hard it can be removed from the moulding tool.
26
Q

Describe the process of 3D printing.

A
  • The 3D printing process builds a three-dimensional object formed from reels of thermoplastic.
  • 3D printers use CAD files which are converted into a series of co-ordinates called G-code that the printer will follow to build up the object in layers.
  • It is also known as additive manufacturing, as the material is added in layers.
27
Q

Describe the process of drape forming.

A
  • Plastic sheet is heated to a softened state, where it can be formed over a mould.
  • It takes on the shape of the mould without stretching the plastic and retains the dimensional thickness.
  • It is a slow process without the need for a vacuum, so is low cost, but it does take time.
  • Used for components with a gentle curve like motorcycle windscreens and bath panels.
28
Q

Exam Style Question:
Describe one advantage of 3D printing in the home.
[3]

A
  • New parts can be made when they are required.
  • Well suited to one-off or small batch production of parts for personal needs.
  • Useful to replace parts of domestic appliances.
  • CAD files can be downloaded from the Internet and shared with others”
29
Q

Describe the process of extrusion.

A
  • Granular plastic is held in a hopper.
  • It is moved by Archimedean screw along a heated tube, called the heating chamber.
  • Once the polymer has been melted it is pushed through a die mould.
  • This creates a continuous flow plastic in a specific shape or profile.
30
Q

Describe the process of injection moulding.

A
  • Granular plastic is held in a hopper.
  • It is moved via an Archimedean screw along a heated tube, called the heating chamber.
  • Once the polymer has been melted, it is pushed into a mould with a hydraulic ram. The use of the hydraulic ram ensures just enough material is injected into the mould each time.
  • The mould is then cooled so that the moulded plastic can be removed.
31
Q

What is injection moulding usually used for?

A
  • Products such as bottle caps, toys and automotive parts are produced with injection moulding.
  • Injection moulding can handle complex parts and shapes to produce consistent products in large quantities.
32
Q

What is extrusion usually used for?

A

It is used for cables, pipes, mouldings and plastic films for packaging.

33
Q

Processes like injection moulding can be __________ in order to increase the output rate and imorove cost effectiveness.

A

automanted

34
Q

Describe the process of line bending.

A
  • Line bending enables thermoplastics, like acrylic sheets, to be folded.
  • A line bender heats a sheet of thermoplastic over a strip heater until it is soft.
  • It can then be bent to a chosen angle. When the plastic cools, it retains the shape.
35
Q

Describe the process of plastic welding.

A
  • Heat softens the polymers and they can be joined with a plastic filler material in the form of a long thin cable.
  • The heat source comes from hot gas welding guns which produces a thin jet of hot air to soften the polymers.
  • Solvent plastic welding can also be used to partially dissolve the plastics, so that they can bond together.
36
Q

Describe the process of resin casting.

A
  • Liquid synthetic resin is mixed with a curing agent, poured into a mould and allowed to harden.
  • Unlike extrusion or injection moulding, which forces plastic into a shape, casting relies on gravity to pull the resin in to all parts of the mould.
37
Q

What is resin casting usually used for?

A
  • Resin casting is used for industrial prototypes, precise models and moulds for dentistry.
  • It also a popular with artists, jewellery makers and hobbyists.
38
Q

What are the advantges and disadvantages of resin casting?

A

Advantages:
- Resin casting produces a strong final product.
- It is has a quick production time.

Disadvantages:
- Its use is limited to smaller scale items.

39
Q

Describe the process of blow moulding.

A
  • A tube of softened plastic, known as a parison is fed into a hollow mould.
  • The parison is pinched at the bottom so it can be filled with warm air and inflates to fill the mould, taking on the shape.
  • After the parison cools, the mould opens and the finished product is trimmed.
40
Q

What is blow moulding usually used for?

A

This method is used for plastic bottles and containers.

41
Q

What is a ‘chinagraph pencil’?

A
  • A wax or grease-based pencil that can write on most non-porous surfaces.
  • Used when marking out on a plastic surface like acrylic.
  • Alternatively, an alcohol-based permanent marker would also work to mark a line to cut to.
42
Q

What are some different tools for cutting plastics by hand?

A
  • Coping saw
  • Junior hacksaw
  • File
43
Q

Plastics are often referred to as ‘______________’ in that they are manufactured with their final surface.

A

self-finishing

44
Q

Plastics can be painted. Before painting, how should the surface be prepared?

A
  • It should be clean and free of grease.
  • Fine abrasive papers rub down the surface to make it smooth and free of debris.
  • A polymer specific primer can be applied.
  • Paint suitable for plastics can be sprayed to produce an even finish.
45
Q

What is hydro-graphic printing? (Surface finish)

A
  • Hydro-graphic printing applies a printed design to a three-dimensional surface.
  • The film containing the design is placed on the surface of water in a dipping tank.
  • The pattern will curve around the surface of the product when submerged.
46
Q

What are vinyl-cut decals? (Surface finish)

A
  • Vinyl-cut decals are printed with a pattern or text onto vinyl with an adhesive backing.
  • They are printed on large rolls and cut using a large format cutter into a variety of shapes.
  • Commonly used on vehicles, window displays and guitars.
47
Q

How are polymers affected by exposure to UV radiation?

A
  • Polymers are affected by exposure to sunlight, UV radiation, and indoor strip fluorescent lighting.
  • The surface of the material takes on a chalky white appearance, the colour fades and the material becomes brittle.
48
Q

How can plastics be protected from degrading from UV radiation?

A

The addition of stabilisers, absorbers and UV blockers can all slow down the degradation process.

AQA GCSE - Design and Technology (25 decks)

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