1.3 Enhancement of Materials

• What is material enhancement

  A way of improving a materials properties to better suit the final product
• What is the meaning of 'inert'

  Chemically inactive
• What are some polymer additives to make them easier and less expensive to process (polymer enhancements)

  Lubricants:wax/calcium stearate (reduces viscosity,lower moulding temp saves energy)

  Thermal antioxidants:prevents polymer oxidising or  discolouring
• What is an additive to enhance polymer aesthetics(polymer enhancements)

  Pigments :tiny particles mixed in to give colour
• What are some additives to improve product funtion(polymer enhancements)

  Antistatics: improves surface conductivity by attracting moisture(no dirt/dust)

  Fillers:provide bulk so less polymer is required, improves properties. Mineral fillers increase conductivity so they will heat up and cool down quickly 
• What are some additives to prolong life(prevent degradation)(polymer enhancements)

  Antioxidants:reduce environmental deterioration

  UV light stabalisers:prevents the polymer chains being broke down by sunlight  
• What are some additives to encourage degradation (polymer enhancements)

  Biodegradable plasticers:make polymers more flexible, softer, easier to break down=faster degradation

  Biro-batch additives:oxy, hydro, Photo dergradable additives
• What are some disadvantages of natural wood


  Strength properties decrease when wet

  Highly combustible

  Fungal/insect attack and rot

  Antisotropic(different properties in different directions)
• What are some ways preservatives enhance wood

  Protect wood from fungal and insect attack(*outdoor timbers*,copper based as it has fungicida properties)

  Pigments can be added to enhance aesthetics(outdoor decking)
• What can wood be impregnated with to make it harder

  Natural polydaccharide

  Increase hardness, toughness and stability
• What ways are woods enhanced

  Preservatives

  Resin & Laminates
• What ways are metals enhanced

  Work hardending( cold working)

  Annealing

  Case hardening (carburising/quenching)

  Hardening & Tempering
• What is heat treatment


  Controlled application of heating and cooling
• What is work hardening

  Cold working metal(bending, rolling,hammering)

  Crystals are distorted and changed improving tensile strength and hardness
• What is the downside of work hardening (cold working metal) 


  Less ductility can result in cracking or damage in the worked area 

  Effects can be removed by annealing
• What is annealing 


  Method of making work hardened metal easier to work with making it less brittle and more ductile 
• How is annealing carried out

  Metal is heated

  Very slowly cooled

  This allows crystals to grow and slowly move into place 
• What is case hardening

  Hardening the surface of steels with a less that 0.4% carbon content

  Greater hardness

  Resistence to surface indentation

  Inner core retains 'softer' properties
• What are the two stages of the case hardening process  

  Carburising

  Quenching
• What is carburising


  Changes the chemical composition of the surface if LC steel so it can absorb carbon, increasing cirface hardness
• How is carburising carried out

  Steel placed in ceramic box

  Box heated 930-950°C

  Carbon atoms diffuse in material's structure to build up surface carbon content  
• What is quenching 


  Hot metal drenched in water

  Fast cooling process

  Seals the hard surface case   
• What is hardening 


  Heating MC and HC steels to alter the crystalline structure increasing hardness but also brittleness
• How is hardening carried out

  Heating HC & MC steels, holding them at that temp and then quenching them in water/oil /salt water bath
• What is Tempering


  Carried out after hardening to reduce some excess hardness and increase toughness
• How is Tempering carried out

  Metal slowly heated to below critical point

  Then slowly air cooled