Polymerisation and plastics

Polymerisation and plastics

1. Polymers

   • A compound that has large molecules
     • It is formed from long chains of smaller molecules called monomers
   • 2 types
     • Addition polymers
       • Made from only one monomer
     • Condensation polymers
       • made from two or more different monomers

2. Polymerisation of alkenes

   • Alkene molecules can be assembled together in large numbers to make a veriety of usefyl polumers such as polythene,polypropelene
   • Ethene molecules can be polymerised to form an addition polymer poly(ethene), commonly known as polythene
     • This is done by heating ethene under pressure. The number of molecules that can join up varies between 2000 and 20000
   • This involves the breaking of carbon double bonds, with each carbon then attracting to another ethene molecule

3. Different polymers

   • Need to know these polymers
   • n sign important to put in, as the polymer molecule is too large to draw out

4. Thermoplastics and Thermosets

   • Thermoplastics
     • Soft when heated
     • Is made up of polymer chains that are not linked, this means that they can slide over each other making them easy to melt
     • PVC, poluthene
   • Thermosets
     • Heat resistant
     • Made of polymer chains with strong cross linkages which holds the structure together making it heat resistant
     • They can be moulded by setting liquid thermoset with heat,chemical rections and radiation
     • Bakelite
     • epoxy resin
     • Once set they cannot be re-melted