GCSE Chemistry (AQA)

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LD & HD Polymers, Thermosetting & Thermosoftening Polymers

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LD & HD Polymers, Thermosetting & Thermosoftening Polymers

10:53 Composition and Use of Different Materials
Spec 4.10.3.3
Previous Clay Ceramics Next Composites
  • Properties of polymers depend on the monomers used and the conditions of polymerization.
  • Polymers are long chains of monomers, with various monomers available for polymer formation.
  • Ethene and propane are examples of monomers with double bonds, affecting polymer properties.
  • Polymerization conditions, such as temperature, influence polymer structure and properties.
  • Polyethylene (PE) is a polymer made from ethene monomers.
  • Polyethylene can be low density (LDPE) or high density (HDPE) based on reaction conditions.
  • LDPE has branched chains, resulting in lower density, while HDPE has less branching and higher density.
  • LDPE is made at higher temperatures and pressures than HDPE, with different catalysts.
  • LDPE is flexible and used for products like bubble wrap; HDPE is strong and used for pipes.
  • Thermo softening polymers melt when heated, suitable for recyclable products like bottles.
  • Thermo setting polymers do not melt when heated, suitable for high-temperature applications like kettles.
  • Thermo softening polymers lack bonds between chains, allowing them to melt; thermo setting polymers have crosslinks, preventing melting.
  • Thermo softening polymers can be recycled; thermo setting polymers are used where melting is undesirable.
  • For exams, understanding the difference between thermo softening and thermo setting polymers is crucial.
  • Example application: choosing a polymer for firefighter uniforms requires considering flame resistance, melting point, and density.
  • Polymer Y, with desired properties, is suitable for firefighter uniforms.

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