Design and Technology students have to be familiar with a range of thermoplastic and thermoset plastics, elastomers, their properties and common uses. This article provides an overview of this material to help students revise for the examination.
A brief introduction to plastics
‘Plastics’ are a type of synthetic polymer (a polymer is a long chain of linked molecules in repeating patterns). Human bodies and those of plants and animals are built from natural polymers. For example, cellulose, protein, and DNA are all made from natural polymers. Rubber is a natural polymer and traditionally comes from latex in the sap of rubber trees (although there are now synthetic forms of rubber).
Scientists can create plastics with almost any properties they want – making them lightweight yet strong, waterproof, mouldable into any shape, and incredibly versatile for product design.
Thermoplastics
- Soften when heated
- Readily available – most common type of plastic
- Typically recyclable (although not always – i.e. acrylic is not)
- Relatively cheap
- Many colours – including transparent / translucent / opaque
- Typically water resistant
- Easily moulded and remoulded (but become weaker each time)
- Can be formed in a variety of ways (vacuum forming, blow moulding, injection moulding)
TIP: Students often find it hard to remember all of the different types of themoplastics listed below. Remembering the general properties of thermoplastics (as described above) can hence be very useful. This means if a question asks: “Why has this plastic been used…” a general answer such as “It is available in a wide range of colours” or “easily moulded” or “readily available” may allow you to gain the mark, even if you can’t remember that precise type of plastic.
THERMOPLASTICS
Acetate
Properties
Uses
Acrylic
Properties
Uses
PVC / vinyl
Properties
Uses
Expanded polystyrene
Properties
Uses
Styrofoam™
Properties
Uses
Coating Styrofoam™ in plaster of Paris makes easy to paint
Polystyrene
Properties
Uses
HIPS
Properties
Uses
Nylon
Properties
Uses
LDPE
Properties
Uses
HDPE
Properties
Uses
PET
Properties
Uses
Polypropylene (PP)
Properties
Uses
This plastic is commonly mentioned in exams!
Polycarbonate (PC)
Properties
Uses
ABS
Properties
Uses
Thermosetting plastics
- Cannot be remelted
- Hard, rigid, and heat-resistant
- Often brittle compared to thermoplastics
- Harder to recycle (however can sometimes be ground into flakes or fibres for composite products etc)
THERMOSETTING PLASTICS
Polyester resin
Properties
Uses
Melamine
Properties
Uses
Urea formaldehyde
Properties
Uses
Phenol formaldehyde
Properties
Uses
Epoxy resin
Properties
Uses
Elastomers
- A type of polymer with elastic properties at room temperature (can stretched or deform and then return to its original shape when the force is removed)
- The word comes from “elastic polymer”
- Often more flexible when heated and stiffer when cold
- Widely used in applications requiring flexibility, vibration damping, or sealing
Thermoplastic Elastomers (TPEs) behave like rubber at room temperature but can be melted and reshaped when heated, making them recyclable and easily formed.
ELASTOMERS
Rubber
Properties
Uses
Latex is the milky white sap from rubber trees (can be synthetic), while rubber is the finished, solid product made from processing latex
Silicone
Properties
Uses
Neoprene
Properties
Uses
TPU
Properties
Uses
Gasket: a shaped piece of material that fills the space between two surfaces to create a seal, preventing leaks of liquids, gases, or pressure. When compressed, the gasket deforms to fill every tiny microscopic gap. They are often clamped between flanges or adjoining surfaces. Examples: rubber rings to make glass jars air tight; rubber rings to stop taps leaking.
Composite materials containing plastic / polymers
COMPOSITE MATERIALS
Fibreglass
Properties
Uses
Carbon fibre reinforced plastic (CFRP)
Properties
Uses
Kevlar® reinforced plastic
Properties
Uses
Braided elastic
Properties
Uses
Other composite products that use plastics include melamine coated chipboard and PE coated card.
Environmental impact of plastics
- Most plastics are made from crude oil / fossil fuels, depleting non-renewable resources
- Poor biodegradability: often take hundreds of years to break down, polluting the environment and accumulating in oceans, soil, and eco-systems
- Health risks from microplastics entering food chains & water systems
- Toxic additives: Chemicals like BPA (bisphenol A) can leach into environment and organisms
Biodegradable plastics (bioplastics)
Biodegradable plastics decompose or break down naturally as a result of microbial action.
BIODEGRADABLE PLASTICS
PLA
Properties
Uses
PHB
Properties
Uses
Polymorph
Properties
Uses
Cornstarch foam
Properties
Uses
While there’s growing development of bio-based plastics made from renewable sources like cornstarch, sugarcane, or algae, these still represent a small fraction of total plastic production.
Recycling codes help to identify different types of plastic
The symbol indicates plastic type, it does not mean the product is made from recycled material, or that it can be recycled in your area.
Sample examination questions (AS Design & Technology)
Other possible answers:
Acetate – transparent / good optical properties allowing product to be viewed easily)
Acrylic sheet – rigid and sturdy so will provide good protection to fragile ceramic balls / creates a durable / lasting /re-usable storage container to suit the premium product
Corriflute – corrugation provides padding helping to protect contents
Foamboard – provides some cushioning / absorbs shock to help protect fragile contents
Thin plywood – creates a durable / lasting / re-usable storage container to suit the premium product
Examiner comment: This question was generally well answered. Most candidates correctly named polypropylene as a suitable material and then often gave easy to work with or aesthetics as a reason for their choice.
Examiner comment: This question was generally, well answered. Most candidates achieved one mark and many gained both marks with ‘heat resistant’ and ‘water resistant’ clearly understood.
Examiner comment: Most candidates understood the function of X.
Examiner comment: Most candidates were able to correctly explain why polypropylene was a suitable material for the stencil. Popular answers included being mouldable, flexible and nontoxic.
Other acceptable answers could include:
The rubber provides friction / grip on the table, preventing it from sliding around
The rubber provides a soft / cushioning effect, preventing the hardwood from scratching the table surface
Examiner comment: Most candidates understood the function of the rubber strip.
Note: A grommet is an eyelet or tube placed inside another hole.
Examiner comment: Most candidates were able to explain why a rubber grommet had been used for the electric cable.
Examiner comment: Most candidates were able to correctly explain at least one reason why Styrofoam is a suitable material for the model of the hairdryer. Styrofoam being easily cut and shaped and having the ability to be painted were popular answers.
Examiner comment: Most candidates were able to name a thermoplastic that could be used to make the lamp casing. Common correct answers included acrylic, polypropylene, polystyrene and acronyms such as HIPS, PVC and ABS. A common incorrect answer was a thermosetting polymer, such as melamine formaldehyde.
Other suitable answers could relate to strength and rigidity (good strength to weight ratio)
Examiner comment: For the material for the frame, correct answers often explained
that a PVC frame would not require a finish that could be expensive to apply, that square section tube would be rigid but lightweight so the display stand could easily be moved around, and that PVC tube comes in a range of colours that would improve the aesthetics of the display stand.
This could also be phrased as a cushioning effect to protect the clamped item from damage.
Amiria has a Bachelor of Architectural Studies, Bachelor of Architecture (First Class Honours) and a Graduate Diploma of Teaching. She is a CIE Accredited Art & Design and Design & Technology Coursework Assessor. Amiria now teaches Art, Design & Technology at ACG Parnell College.