1.2 Performance Characteristics of Materials

• What is the meaning of air seasoning  

  Traditional method of drying wood.

  Stacked under shelter away from rain

  Air circulation between the planks to remove excess moisture
• Why is air season wood used for outdoor products

  It is seasoned to the same moisture content as it's surroundings

  Less prone to defects
• What does seasoning wood do

  Remove excess moisture by 80-90%
• Which polymer based sheet/film can biodegrade 

  Cellulose acetate since it comes from a natural source  
• Name 3 types of Paper & Boards

  Cartridge paper

  Tracing paper

  Watercolour paper

  (Bleed proof paper)
• Name 3 types of polymer based sheet and film 

  Foam Board

  Styrofoam

  Cellulose acetate
• What is the 'grain' on wood

  Wood fibre that grow along the length of the tree/branch 
• What it the meaning of tracheids

  Hollow cells that the wood fibres(grain) consist of
• What is the meaning of kiln seasoning

  More expensive but controlled method of removing excess moisture from wood

  Very quick(just a few weeks)
• How is kiln seasoning carried out

  Wood planks are stacked unto trolleys

  Placed in the kiln

  Temperature and humidity are controlled

  Dried for a couple of weeks 
• What are kiln seasoned products used for 

  Indoor products such as furniture because they have been season to meet indoor conditions

  Have LOWER moisture content than air-dried wood
• What could happen if unseasoned wood is placed in a heated room   

  It will twist, wrap, cup or bow when drying

  Cracks or gaps may appear
• What are some advantages of seasoning wood 

  Greater immunity from decay

  (Increased resistance to rot)

  Woods become less corrosive to metals

  Helps preservatives penetrate  
• How can wood be toxic

  Dust from wood

  Sap

  They can be toxic to workers manufacturing
• What does the toxicity of wood depend on


  The species of tree
• What is the maximum exposure both soft and hardwoods can be at

  5mg per cubic metre
• What type of issues can both soft and hardwoods cause 

  Respiratory irritation

  Carcinogenic (Hardwoods)
• What legal act is the safety of wood exposure under

  The Control of Substances Hazardous to Health(COSHH)
• What protections systems are put in place to help keep workers safe when working with wood

  Air ventilation systems

  Personal protective equipment
• What is rough sawn wood

  Comes directly from seasoning

  Has rough surfaces

  Normal sizes not accurate finished sizes
• What is planed square edge wood

  One edge is planed accurately the rest are rough sawn.

  Planing removes 3mm from the original size
• What is planed all round (PAR)

  All the edges, sides are planed square, straight and level

  Smooth finish

  3mm smaller than original rough sawn
• What is the issue with manufacturing with natural wood

  It's only available at the maximum width of the tree

  When being joined, the end grains must go in opposing directions to stop the internal forces pulling the wood in one direction
• What are the advantages of using manufactured boards

  Very stable (no temp/humid) 

  Uniform strength(no grain)

  Less expensive

  Veneers can be applied to enhance aesthetics
• Mouldings


  Skirting boards or wooden trims made from softwood
• Types of mouldings


  • Standard
  • Decorative
• Stock forms of metal

  Structural(angular shapes)

  Bar(solid)

  Tube(hollow)

  Plate(thicker than 3mm)

  Sheet(large flat sections, from <1 - 3mm)
• What is cracking


  The process of breaking down large hydrocarbons into smaller, more useful forms
• What is an oxy-degradable polymer


  Polymer breaks down into a fine powder with exposure to oxygen
• What is a photodegradable polymer


  The polymer bonds are weakened and break down with exposure to UV light e.g sunlight
• What is a hydro-degradable polymer

  Polymer breaks down with exposure to water

  Often more quickly that oxy-degradable polymers
• What are some implications of bio-polymers and biodegradable polymers 

  Biodegradable polymer (methane gas=global warming)

  Both cannot be recycled and contribute to a throw away culture
• Name 3 biodegradable /bio polymers

  Corn starch polymer

  Potatopak

  Lactide (PLA & Cellulose based)