Enhancement Of Materials Flashcards
What is the role of antioxidants in polymers?
Helps reduce environmental deterioration of the polymer from exposure to oxygen.
What are the effects of polymer degradation?
Degradation leads to polymers becoming brittle, discolouring, and developing surface cracks.
What do UV light stabilisers do?
UV light stabilisers prevent the polymer chain from being broken down by UV rays in sunlight.
What happens to polymers when exposed to UV light?
Polymers become discoloured and brittle; white pigment becomes yellow and other colours turn milky or faded.
Where are UV light stabilisers often used?
They are often used in public seating and uPVC windows and doors.
Fill in the blank: Antioxidants help to reduce environmental deterioration of the polymer from exposure to _______.
oxygen.
What are antistatics used for?
Antistatics are used to give the polymer greater resistance to static.
Why do polymers need antistatics?
Polymers have poor electrical conductivity, so static can easily build up.
What do antistatics help to reduce?
Antistatics help to reduce static discharge/shock.
What are flame retardants used for?
Flame retardants help to reduce the likelihood of the spread of fire.
Which materials are commonly used as flame retardants?
Bromine or metals (such as Asbestos in the past) are commonly used.
What is the purpose of plasticisers?
Plasticisers allow the polymers to become less hard and brittle.
Where are plasticisers extensively used?
Plasticisers are used extensively in the food industry for cling film and food packaging.
What is the dual function of fillers?
Fillers bulk out the product or improve the polymer properties.
What are common bulk fillers?
Common bulk fillers include sawdust and wood flour.
How do mineral fillers affect thermal conductivity?
Mineral fillers such as chalk and clay can increase thermal conductivity.
What is the benefit of increased thermal conductivity in polymers?
Increased thermal conductivity means they heat up and cool down more quickly, enabling shorter mould cycle times.
What is ‘annealing’?
Annealing is used to make hardened metal easier to work by making it less brittle and more ductile.
What are the advantages of annealing?
Increases ductility, increased corrosion resistance and toughness.
What are the disadvantages of annealing?
It can be time-consuming, expensive, can cause defects
