C2 - Polymers

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  • Created by: Katie
  • Created on: 19-05-13 16:44
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  • C2 - Polymers
    • Low density polymer
      • Structure - branched polymer
      • How do you make them?
        • Very high pressure with a trace of oxygen.
      • Properties - soft and flexible
      • Weak intermolecular forces between the polymer chains, s less energy is needed to melt them.
    • High density polymer
      • How do you  make them?
        • A catalyst of 50'C, slightly raised pressure.
      • Structure - tightly compact chains
      • Properties - hard and stiff.
      • Strong covalent bbonds (cross links) between the polmer chains, more energy is needed to melt them.
    • Thermosoftening Polymer
      • How do you make them?
        • Individual polymer chains tangled in a web.
      • Properties - melts at low temperature, it can harden when cooled.
      • Weak intermolecular forces between the polymer chains, so less energy is needed to melt them.
    • Thermosetting Polymer
      • How can you make it?
        • Strong covalent bonds between polyer chains.
      • Properties - hear resistant, rigid, charred when heat at a high temperature.
      • Strong covalent bonds (cross links) between the polymer chains, more energy is needed to melt them.
    • We can make polymers from chemicals made from crude oil. small molecules called monomers join together to ake much bigger molecules called polymers.
      • As the monomers join together they produce a tangled web of very long chain molecules. the properties of a polymer depend on; the monomers used to make it and the conditions we choose to carry out the reaction.
    • Polymers
      • The Low density polymers have very high pressures and a trace of oxygen. the polymer chains are branched ad they can't pack closely together.
      • The high density polymers catalyse at 50'C and have a slightly raised pressure. they are made up of straighter poly-molecules. they can pack closer together and they have a hgih softening temperature and they are stronger than low density polymers.
      • Some can soften easily and they reset when they cool down - thermosoftening polymers.
      • Some don't melt when heated - thermosetting polymers.
    • The atoms in polymer chains are held together by very strong covalent bonds. this is true for all plastics. But the size of the forces between polymer molecules in different plastics can be different.
    • In thermosoftening polymers the forces between the polymer chains are weak. When we heat the polymer, these weak intermolecular forces are broken. tThe polymer becomes soft. When the polymer cools down, the intermolecular forces bring the poymer molecules back together. then the polymer hardens again, and it can be remoulded.


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