CIE A Level Chemistry (9701) 2019-2021

Revision Notes

7.7.6 Properties & Structure of Polymers

Properties & Structure of Polymers

  • The polymerisation method can often determine the properties of the resulting polymer
  • Reaction condition in the polymerisation can have a big impact on a polymer’s ability to pack neatly
  • Altering reaction conditions can lead to high and low density polymers
  • Low density polymers are made at high temperatures and pressures
    • They contain many side chains, which leads to poor packing arrangements and disorder within the polymer
  • However, high density polymers are made at lower temperatures, pressures and in the presence of a catalyst
    • This higher level of control leads to a much better packed and stronger resulting polymer

Thermoplastic polymers

  • These polymers are also known as thermosoftening polymers
  • They can be melted and formed into a new shape
  • For example low density polyethylene is a thermosoftening plastic
    • It can be melted and formed into a newly shaped object

Thermosetting polymers

  • Thermosetting polymers differ in the fact that once they ‘set’ their shape cannot be altered
  • They have many applications where heat resistant materials are required
  • Once the polymer is applied to a surface, cross links start to form between the polymer chains
  • This sets the polymer and prevent being moulded for an alternate use

Author: Francesca

Fran has taught A level Chemistry in the UK for over 10 years. As head of science, she used her passion for education to drive improvement for staff and students, supporting them to achieve their full potential. Fran has also co-written science textbooks and worked as an examiner for UK exam boards.
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