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  • 4 Polymers

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    DRAF

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    4.1 Design contexts

    Do some research to find out how consumers can responsibly dispose of products that are made of polymers.

    Apply it

    4.1 Design contexts

    By the end of this section, you should know:

    a range of contexts where polymers are essential to the success of a product.

    Learning objective

    Most synthetic polymers are made from oil-based petrochemicals. However, alternatives that use natural and sustainable sources are becoming increasingly available. Designers and engineers use a wide variety of polymers every day to make commonplace products we take for granted: toothbrushes, toothpaste tubes, shower gel containers, hair brushes and hairdryers.

    There are two main categories of polymer that you need to know about: thermoforming polymers and thermosetting polymers. You will also need to learn more about biodegradable alternatives.

    Design contextsThe first polymer Bakelite (a phenol-formaldehyde resin) was invented in 1907. It was mostly used to case electrical components in radios and other electrical devices, but it was also used to manufacture toys and jewellery. Bakelite was non-recyclable and this concerned environmentalists. Over the last 100 years, the list of polymers has expanded. At first, products made from polymers only used a limited range of manufacturing processes, but the number of techniques available today makes it possible to make complex products.

    As already mentioned in Topic 1.10, polymers have a wide variety of uses in everyday life. Think about the home environment and consider the following questions.

    How many of your personal possessions are made from polymers?

    Of these, how many polymers can you name?

    Do you know the properties of some of these polymers?

    Count how many items made from polymers you can identify in your home. Select one and complete a detailed product analysis. Consider how the item has been made.

    Getting started

    Bakelite: a thermosetting phenol-formaldehyde resin.

    Non-renewable resource: natural resources, such as crude oil, that take millions of years to form and are used up more quickly than they can be replaced.

    Key terms

    Polymers are now used in:

    medicine: for artificial limbs, tablet coatings, blister packs, syringes and heart valves

    household goods: kitchenware, laptops and personal music players

    building materials: including home insulation.

    The list is endless. With crude oil being a non-renewable resource, it is becoming increasingly important for polymers to be recycled and cause less impact on the environment in which we live.

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    4 Polymers

    Checkpoint

    Strengthen

    S1 Name two products that are made of polymers.

    S2 Describe the benefits of using polymers compared to more traditional materials.

    Challenge

    C1 Why have polymers become more popular for the production of products?

    Thermoforming polymers were covered in the core content section of this book. To remind yourself, look at pages 4346.

    Link it up

    4.2 Sources and properties

    By the end of this section, you should know:

    the types, properties and structure of thermoforming polymers and thermosetting polymers not considered in Topic 1.10

    the components and manufacturing processes associated with polymers

    the advantages and disadvantages of using polymers for different applications

    the social and ecological footprints of polymers.

    Learning objectives

    Thermoforming polymers are used in many different products. When designing a product, the designer will need to select the most appropriate polymer for the task. Designers will need to factor in many design constraints such as cost, manufacturing methods and material properties. In this section you will learn about other polymers that are commonly used in everyday products.

    Design constraint: limitation on the design and manufacture of the product.

    Key term

    Summary

    Key things to remember:

    There are two main categories of polymer: thermoforming polymers and thermosetting polymers.

    When they were first invented, polymers were non-recyclable. Now, however, polymers made from renewable resources are being used so they do not cause as much environmental damage.

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    4.2 Sources and properties

    Thermoforming polymers

    Thermoforming polymer

    Form Properties Common uses Advantages/disadvantages

    Polyvinyl chloride (PVC)

    Powder, granules and sheet

    Chemical and weather resistant

    Window frames, cable insulation, pencil cases and drainage pipes

    Can be formed using a wide range of techniques

    Needs UV stabilisers to stop material fading in sunlight

    Acrylonitrile-butadiene-styrene (ABS)

    Granules, tube and sheet

    High impact strength, lightweight, hard and durable

    Computer casings, mobile phones, safety helmets and car bumpers

    Excellent impact strength Can be formed using a wide range

    of techniques Can be coloured using pigments More expensive than alternative

    materials

    Polyethylene terephthalate (PET)

    Granules and sheets

    Lightweight, strong and food safe

    Food packaging, bottles, electronic component coatings

    Excellent visual clarity Can be coloured using pigments

    Urethane/ polyurethane

    Liquid, sheet, foam and granules

    High-load resistance, high-wear resistance, flexible and good electrical resistance

    Bags, varnish, wheels and furniture foam

    Can be made into very thin sheets to produce carrier bags

    Governments have imposed a charge for carrier bags to reduce landfill and promote reuse

    Fluoroelastomer Sheet and tube

    Heat, chemical and solvent resistant

    Heat shrink tubing, car hoses, chemical-resistant gloves, gaskets

    Can be used to tie wiring looms together

    Differently sized material is required depending on amount of shrink fit required

    Rigid polystyrene (high-density polystyrene)

    Granules and sheets in a wide range of colours

    Lightweight, food safe, heat resistant

    Food packaging, such as coffee cups

    Can be recycled at school where equipment available

    Difficult to recycle if contaminated by food

    Expanded polystyrene

    Beads, sheets and blocks

    Lightweight, buoyant, tough but breaks easily

    Packaging, swimming floats, cups, sound insulation, heat insulation, beads in bean bags

    Can be vacuum formed Excellent thermal properties that

    are useful in drinking cups Difficult to recycle if

    contaminated with food

    StyrofoamTM

    (extruded polystyrene EPS)

    Sheets Lightweight, buoyant, heat insulation and can be easily shaped using workshop tools to make models

    Fast-food packaging, packaging of audio-visual equipment, silk flower holders

    Can be easily formed using school workshop tools and equipment

    Cutting by hot wire requires good ventilation due to fumes

    Table 4.2.1 A summary of the different types of thermoforming polymers

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    4 Polymers

    Thermosetting polymers are commonly used as a resin glue to bond particles and sheets of timber together in manufactured boards. Polyester resin is also combined with glass fibres to form glass reinforced plastic (GRP), a composite material. The glass fibre strands are fixed in place once the polyester resin is hardened and toughened. GRP is very strong and lightweight. The direction of the glass strands is random and this is what provides GRP with uniform strength. GRP is commonly used in low-production products such as sport cars and boats as it can be formed into many shapes. A polyester gel coat resin is used to give the GRP a smooth finish. The gel coat layer can also be coloured using pigments. Urea formaldehyde is used in the moulding of products, such as an electrical wall socket. It is also used as an adhesive in manufactured boards.

    Sources and origins of polymersMost synthetic polymers are made from crude oil. Oil is a non-renewable resource, most of which is found deep in the ground. Oil rigs are used to drill for oil in the rock below the sea. On land, pumps are used to extract oil from wells. The largest oil-producing nations are Russia, Saudi Arabia and the United States.

    Thermosetting polymers

    Composite material: a material made from a combination of two or more materials.

    Key term

    Thermosetting polymers were covered in the core content section of this book. To remind yourself, look at pages 4445.

    Link it up

    The properties of acrylic make it an ideal material for rear car light covers, but unsuitable for lights on the front of a car. Analyse the parts made from polymers on a family member or relatives car. Consider the properties of polymers that make them suitable for each part.

    Apply it

    What are the advantages or disadvantages of StyrofoamTM?

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    4.2 Sources and properties

    Hydrocarbon: a compound consisting of hydrogen and carbon. Qualitative: measuring results by quality.

    Key terms

    Figure 4.2.1 The worlds biggest oil reserves. Why is oil referred to as black gold?

    Canada 32.14.2%

    0.00.0%

    USA 30.98.7%

    Kazakhstan 39.82.1%

    Nigeria 37.22.9%

    Libya 46.42.0%

    Russia 77.412.9%

    UAE97.83.3%

    Iraq 115.03.1%

    Kuwait101.53.1%

    Iran137.05.2%

    Venezuela

    Oil reserves in billions of barrelsOil production (current global market share)

    211.23.2% Saudi

    Arabia

    264.512.0%

    Explain one reason why oil refineries

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