Part 2: Types of Materials

Mechanical Properties of materials Hardness: ability to resist indentation or abrasion Elasticity: ability to return to original shape after undergoing a constraint Resilience: ability to resist shock without breaking Ductility: ability to be stretched without breaking Malleability: ability to be flattened or bent without breaking Stiffness: ability to retain shape when subjected to various constraints

Wood Wood → material from trees Two Types Hard wood → high hardness; comes from deciduous trees (i.e. maple) Soft wood → low hardness; comes from conifer trees (i.e. pine) Mechanical properties of wood Vary with Tree species Speed of Growth (dependent on environmental conditions) and Injuries Water content of the wood

Types of Wood Hardwood Softwood

Wood Other properties of wood Hardness, Elasticity, Resilience and Toughness Low Thermal and Electrical Conductivity Ease it can be shaped Colour and Shades Lightness

Modified Wood Is treated wood or a material made from wood mixed with other substances Made by gluing together pieces, sheets or residue of wood left over after timber harvesting Properties of modified wood more consistent than regular wood Examples Plywood, Particleboard, Fibreboard

Types of Modified Wood Particleboard Plywood

Metals and Alloys Material extracted from mineral ore Properties: Shiny Malleable Ductile Good electrical conductivity Mixture of a metal with one or more other substances These other substances can be metallic or non-metallic Two types Ferrous Alloy (main component is iron) Nonferrous Alloy (main component something else than iron)

Plastics Made from fossil fuels Monomers are extracted and arranged in chains to form polymers Plastics → made from polymers which other substances can be added to, to get specific properties Are poor conductors of heat and electricity

Two Categories of Plastics Thermoplastics Thermosetting Plastics Plastic that becomes soft enough when heated to be molded/remolded and that hardens enough when cooled ¾ of plastics produced in the world Some are recyclable (need to have sign) Plastic that remains permanently hard (even when heated) Melamine; polyesters Harder and more resilient than thermoplastics Not recyclable in Quebec