Design and Technology Materials Notes
MATERIALS:
WOODS:
Hardwoods:
Oak - desirable grain, hard, tough, weather resistance, can corrode steel because of tannic acid.
Mahogany - dark cherry wood colour, interlocking grain
Beech - whitish colour when steamed, tough, close grained, hard.
Jelutong - fine texture, straight grain, easy to cut, can be brittle, white coloured.
Balsa - off white colour, straight grain, low density, lightweight.
Softwoods:
Pine/Redwood - straight grain, can be knotty with resinous knots.
Cedar - Straight grain, can corrode ferrous metals because of acidity, low density, good sound dampening.
Larch - Hard, tough, attractive grain, can be used outside.
METALS:
Ferrous Metals:
Mild steel - ductile, high tensile strength, tough, malleable, poor resistance to corrosion. 0.15% to 0.30% Carbon.
Medium carbon steel - Harder than mild steel, less ductile, malleable and tough. 0.30% to 0.70% Carbon
Cast Iron - Hard outer skin but brittle core, good under compression. 3.5% Carbon
Non-Ferrous Metals:
Aluminium - Lightweight, ductile, malleable, corrosion resistant, electrical and thermal conductor, can be MIG AND TIG heat welded.
Zinc - low melting point, good corrosion resistance, used for galvanising steel.
Tin - Ductile, malleable, low melting point, corrosion resistant.
Copper - Ductile, Malleable, tough, corrosion resistant, good electrical and thermal conductor, can be soldered and brazed.
Alloys:
Stainless Steel - tough, hard, corrosion resistant, 18% chrome and 8% nickel.
Duralumin - 4% Copper, 1% magnesium and manganese. Equivalent strength properties to mild steel but more lightweight, ductile, and work hardens.
Brass - Corrosion resistant, good electrical and thermal conductor, low melting point, casts well. 65% copper, 35% Zinc.
POLYMERS:
Thermoplastics (can be reshaped and reheated):
PMMA (Acrylic) - tough, hard, good chemical resistance, available in translucent and transparent colours.
LDPE - Very tough, good chemical resistance, weatherproof, low level of rigidity. Used for single use plastics.
HDPE - Available in translucent and transparent, weatherproof, tough, good chemical resistance, used for more long lasting products such as buckets and toys.
PET - available in transparent form, hard, tough, good chemical resistance, single use drink bottles.
PVC - tough, flexible, good weathering resistance, good chemical resistance, hose pipes, medical grade tubing, inflatable products.
uPVC - rigid, opaque, tough, hard, good chemical and weathering resistance, window frames, external doors, and water pipes.
PP - Translucent and transparent, good chemical resistance and fatigue resistance for hinges, tough, rope, folders, medical equipment.
ABS - Tough, hard, opaque, rigid luggage, handles, computer housings, control casings.
Thermosetting Plastics:
Epoxy Resin - Rigid, clear, hard, tough, chemical resistant, adhesives, surface coatings, pacemakers and aerospace applications.
Urea Formaldehyde - Hard, heat resistant, good electrical insulator, brittle, electrical fittings, adhesives.
Polyester Resin - rigid, heat resistant, chemical resistant, brittle, castings, car parts, boat hulls.
Elastomers:
Natural Rubber - high tensile strength, low elongation, good hardness, tough, electrical insulator, good cold resistance, tires, hoses, footwear.
Neoprene - good thermal resistance, toughness, good oil and chemical resistance, excellent weather resistance, good abrasion resistance, electrical insulator, wetsuits, laptop cases, shock absorbers.
COMPOSITES:
Carbon fibre re-enforced plastic - Lightweight, corrosion resistant, tough, good compressive strength, low thermal expansion, bicycle frames, tennis racquets, racing car bodies.
Glass re-enforced plastic - Lightweight, corrosion resistant, tough, hard, low thermal expansion, good compressive strength, boat hulls, kayak shells.
MDF - Good strength in all directions, easy to cut and shape, smooth surface is good for veneers.
Hardboard - one smooth surface, good strength in all directions, used for furniture backing.
Chipboard - good strength in all directions, easy to cut, not aesthetically attractive in its raw form, often veneered.
Plywood - good strength in all directions, no grain weakness, always has an odd number of layers, tough material, used for structural work.
PAPERS:
Layout paper - thin translucent paper with a smooth surface, used for sketching.
Tracing paper - slightly thicker than layout paper but still translucent for copying imaging.
Copier - used for general purpose and printing.
Cartridge paper - off white paper usually with a slightly textured surface used for sketching and rendering in pencil.
Bond paper - high quality paper, bright color holding, durable surface, used for letterheads flyers and writing paper
Coated paper - restricts restricts the amount of ink absorbed into the paper and/or how the ink bleeds into the paper, good for sharp complex images. Used for spirit-based marker rendering, photographic printing, high quality graphics, duplex card for juice or milk cartons, disposable cups.
BOARDS:
Mounting board - made made from compressed fine cotton fibers to produce a rigid board used for presenting artwork, picture mounting, modeling.
Corrugated Board - usually with cotton board outer layers and a corrugated middle layer, giving the material the ability to provide protection against impact. Used for protective packaging, model making, prototyping ideas, food packaging such as takeaway boxes.
Foam board - two outer layers of card with a foam middle core, available in a range of thicknesses. Used for mood board backing, presentation boards and modeling.
Folding box board - multiple layers of pulp with the top layer usually bleached or pigmented, good thickness for a good printing surface. Can be creased and embossed. Lightweight, high stiffness. Used for packaging products, supermarket food packaging, pharmaceutical packaging.
Foil-lined board - board with foil applied to either one side or both sides to provide a water resistant and/or heat resistant layer. The foil can be removed before recycling the paper pulp. Used for drinks packaging, milk cartons, takeaway box lids.
TEXTILES:
NATURAL FIBRES:
Cotton - good absorption, breathable, low elasticity, non-allergenic, tendency to crease, no static cling, holds up to 27 times its own weight in water.
Linen - good absorbency, can hold up to 20 times its weight in water, breathable, high durability, lightweight.
Wool - good thermal insulator, high breathability, good resistance to creasing, good absorption, some elasticity, good flame resistance, low durability.
MAN MADE FIBRES:
Nylon - does not absorb water, very durable, good elasticity, good tear resistance, does not crease, not very breathable, can create static.
Polypropylene - does not absorb moisture, high durability, very lightweight, not very breathable, used for sporting and active wear.
Polyester - good elasticity, good crease resistance, very durable, poor moisture absorption, quick drying, produces static, often blended with cotton to get enhanced properties. Used for jackets and clothing.
SMART MATERIALS:
Thermo-ceramics - metal powder is placed in a mold or die under high pressure. The high pressure forces the particles two Bond. Thermo ceramics are very hard and stable at high temperatures up to 100 degrees Celsius. They are used for turbine blades in jet engines, turbo charges and racing cars, and tips on cutting tools such as drill bits.
SMA - changes shape in response to a change in temperature or electrical input. For example, Nitinol wire in dental braces changes length in response to a change in temperature. It is used in dental braces, self-closing Windows, arrow plane wing flaps, and Bone plates.
Reactive glass - glass reacts to a change in temperature by changing the tent. When the glass gets hot, the Glass darkens to block the heat from entering through the glass. It is used in apartment for office block Windows, conservatories and glass roofing.
LCD - liquid crystals change color when an electric voltage is applied. The cell turns from light to dark. It is used in digital clocks and watches, computer or laptop screens, car audio displays, and finally calculator displays.
Photochromic material - changes colour with light intensity, used in welding goggles, reactive spectacle lenses, car rear view mirrors.
Thermo-chromic material - changes colour in response to a temperature change. Used for baby feeding spoons, bath mats, thermometers and battery charge indicator strips.
QTC - insulating Rubber containing tiny metal particles, the material is pressure or force sensing. When there is a change in the applied pressure or force, the material changes from an electrical insulator to a conductor. Used in touch screen technology and speed controllers in power tools.