• 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