Material Sources & Properties
GCSE — 2.1.2 In-depth Knowledge: Product Design
Metals — sources and classification
- Ferrous metals contain iron
- Non-ferrous metals do not contain iron
- Alloys are combinations of a base metal with other metals or non-metals
- Metals are sourced from ores, which are a natural resource and will eventually run out
Heat treatment of metals
Metals can be conditioned using heat treatments to change their properties:
| Treatment | Process | Effect |
|---|---|---|
| Annealing | Heat then slowly cool the metal | Removes stress, makes softer, refines structure |
| Normalising | Heat then cool at room temperature | Reduces hardness, increases ductility |
| Hardening | Heat then rapidly cool by submerging in liquid or oil | Increases hardness |
| Tempering | Heat to high temperature then air-cool (applied to steel/cast iron) | Increases toughness, reduces hardness and brittleness |
| Case hardening | Add carbon to surface, heat and quench | Hardens the surface of an alloy while keeping a tough core |
Natural and manufactured timber — sources
- Natural timber is grown on trees
- Manufactured timbers are man-made
- Timbers are categorised into hardwoods and softwoods
Hardwoods come from trees that shed leaves in colder months. Slower-growing and more expensive. Common examples: oak, beech, balsa, jelutong.
Softwoods come from coniferous trees — green all year with pinecones and needles. Faster-growing, more readily available and less expensive. Common examples: Scots pine, western red cedar, Parana pine.
Hardwoods and softwoods must be seasoned before use (kiln drying or air drying) to remove moisture and prevent shrinkage.
Manufactured boards are made from recycled wooden waste mixed with adhesive. Popular types: MDF, chipboard, hardboard, plywood.
Timber properties
- Hardwoods tend to have close grain and are normally polished to enhance their natural aesthetic
- Beech has a pink tint; oak is light-mid brown; balsa is pale with widely-spaced grain
- Softwoods tend to be yellow/pale with contrasting grain and sometimes knots
Polymers — sources
- Polymers that can be heated and shaped repeatedly = thermoplastics / thermoforming
- Thermosetting polymers can only be heated and shaped once
- Some polymers are natural, some are synthetic
Common thermoplastics: acrylic, polythene, polypropylene, Styrofoam, polystyrene, nylon
Common thermosets: melamine, urea formaldehyde, epoxy resins
Papers and boards — sources
- Paper is made from wood pulp
- Paper is fully recyclable, reducing the need for wood fibres from trees
- Paper is measured in gsm (grams per square metre)
- Card (board) is thicker and measured in microns
- Corrugated card is made by adding a ‘wavy’ layer between two flat layers — brilliant for packaging
- Paper and card need to be scored before bending
Papers and boards can be:
- Textured, embossed, with specialist coatings
- Laminated to retain liquid and resist absorbency
- Printed on for graphics and branding