Hardwood Types and Uses

• Hardwood comes from broad leaf, deciduous trees.
• Hardwoods grow slowly, making them generally more expensive.
• Hardwoods typically grow in warmer climates.
• Hardwoods have environmental concerns due to their slow growth and long replacement time.
• Hardwoods often have a close grain.

Oak

• Hard, tough wood with an attractive grain and good weather resistance.
• Contains tannic acid, which corrodes steel screws or fixings.
• Used in furniture, flooring, and boat building.

Mahogany

• Can contain locking grain, making it more difficult to work with.
• Rich, dark red color.
• Used in indoor furniture and veneers on manufactured boards.

Beech

• Tough, close-grained, and hard.
• Available steamed (white color) and unsteamed (pink tinge color).
• Used in chairs and chopping boards.

Jelutong

• Fine texture, straight grain, and easy to work with.
• Used in pattern making and wood carvings.

Balsa

• Off-white pinkish color with a straight grain, low density, and lightweight.

• Used in model making and structures.

• Softwoods come from coniferous trees.

• Softwoods grow faster than hardwoods.

• Softwood is a managed resource due to careful planning.

• Coniferous trees have needles instead of leaves.

Pine/Redwood

• Straight grain, knotty, and can contain resinous knots.
• Used in construction work, roofing beams, timber frame construction, and interior joinery.

Cedar

• Straight grain but can corrode ferrous metals due to its acidic nature.
• Low density and good sound damping properties.
• Used in exterior building cladding, sheds, and greenhouses.

Larch

• Hard, tough, with an attractive grain pattern that fades to silver upon outdoor exposure.
• Used in garden furniture, decking, and fencing.

Metals

• Ferrous metals contain iron, rust, and are magnetic.

Cast Iron

• White cast iron contains 1.7-2.9% carbon.
• Grey cast iron contains 2.5-4% carbon.
• Has a hard outer skin but a brittle core, with 3.5% carbon content.
• Good under compression

White Cast Iron

• White cast iron is not easy to work with because it's brittle and hard.
• It's almost impossible to weld and has high thermal conductivity.
• Used in cars and cookware where heat may be an issue.

Grey Cast Iron

• The most useful type of cast iron, as it can be cast into intricate shapes.
• Often used for components on machines, such as the tail stocks on lathes.
• Relatively corrosion resistant compared to steel.

Mild Steel

• Also known as low carbon steel.
• Contains 0.15-0.30% carbon.
• Steel is an alloy of iron and carbon.
• The more carbon added, the harder the steel becomes.
• Mild steel has many engineering applications and is easily worked.
• Cannot be heat treated.
• Prone to rusting due to the iron reacting with oxygen.
• Oxidation can be prevented by applying a layer of paint (barrier), galvanization (zinc layer), or plastic coating (thermoplastic).
• Used in nuts, bolts, and washers.

Carbon Steel

• Medium carbon steel contains 0.30-0.70% carbon.
• High carbon steel contains 0.70-1.40% carbon.
• Can be heat treated, unlike mild steel.
• Medium carbon steel is used in garden tools.
• High carbon steel is used in items that need to be much harder, like drill bits.
• Prone to rusting, so it must be painted or galvanized.

Polymers

• Thermoplastics can be formed using heat into a variety of shapes.
• Thermoplastics can be reheated and reshaped many times, and can be recovered and recycled easily.
• Made from long chains of molecules held together by small cross-links.
• Polymer chains are held together by mutual attraction called Van der Waals forces.
• When heated, the bonds between the chains of molecules weaken, and the material becomes pliable.
• Once cooled, the chains reposition, and the plastic becomes hard.

Acrylic

• Stiff, hard, durable, and a good electrical insulator.
• Can be easily scratched, brittle, and break/splinter easily.
• Used in lighting, CD cases, and baths

High-Density Polyethylene (HDPE)

• Good electrical insulator, chemical resistant, and impact resistant.
• Color tends to fade over time and can break under stress.
• Used in water tanks, buckets, and bowls.

Low-Density Polyethylene (LDPE)

• Good electrical insulator, chemical resistant, and flexible.
• Color tends to fade over time and can break under stress.
• Used in washing-up liquid bottles, cable insulation, and packaging film.

PET

• Good alcohol and oil barrier and chemical resistance.
• High impact resistance.
• Can discolor and needs treatment to prevent taste problems in food containers.
• Used for fizzy drinks bottles.

PVC

• Good chemical and water resistance.
• Stiff, tough, and hard.
• Can become brittle over time, and ultraviolet light causes degradation.
• Used in electrical wiring insulation, pipes and guttering, and floor covering.

PP (Polypropylene)

• Light, hard, and impact resistant.
• Ultraviolet light causes degradation, and oxidation can be a problem during manufacturing.
• Used in medical syringes, carpets, and kitchenware.

PS (Polystyrene)

• Compressed: light, hard, stiff, and low impact strength.
• Expanded: lightweight and a good insulator.
• Crumbles and breaks, and easily ignites.
• Used in packaging and insulation.

ABS

• Chemical resistant, hard, and tough.
• UV light causes degradation.
• Used in mobile phones and safety helmets.

Smart and Modern Materials

• Smart materials' physical properties change in response to an input or change in environment.
• Modern materials are developed through new and improved processes.

Reactive Glass

• Changes tint in reaction to a change in temperature.
• Darkens when hot to block heat.
• Some reactive glass applications (welding masks) contain electronics and batteries to react to light, rather than heat.
• Used in apartment or office block windows, glass roofing, and windows.

Liquid Crystal Displays (LCD)

• Change color when an electric voltage is applied; the cell turns from light to dark.
• Liquid crystals are organic, carbon-based compounds that can exhibit both liquid and solid crystal characteristics.
• Molecular rearrangement within the liquid crystal causes light to darken the display when voltage is applied.
• Used in digital clocks and watches, and computer and laptop screens.
• Ideal for portable electrical devices, such as mobile phones, because they need very small amounts of voltage.

Photochromic Materials

• Changes color with light intensity.
• Photochromic paint contains pigments which change color according to light conditions.
• Used in welding goggles and security markers that show under UV light.

Thermochromic Materials

• Changes color in response to temperature change.
• Used in room thermometers, baby feeding spoons, and food packaging to tell whether food is safe to eat or not.