Polymers

Polymers

1. THERMOSOFTENING PLASTICS

   • Individual tangled chains of polymers
     • Held together by WEAK intermolecular forces
     • Free to slide over each other
   • Forces between the chains are really easily overcome
     • So you can easily melt the plastic
   • When it cools it hardens into a new shape
     • You can melt and remould them as many times as you like
   • WEAK FORCES

2. THERMOSETTING PLASTICS

   • STRONGER FORCES
   • Have crosslinks to hold the chains firmly togther
     • So there are STRONGER intermolecular forces between the polymer chains
       • Solid structure
   • Forces are too strong to overcome
     • Doesn't soften when heated
   • Strong, hard and rigid

3. REACTION CONDITIONS

   • LOW DENSITY POLYTHENE
     • Made by heating ethane to 200C
     • Made under high pressure
     • Flexible
       • Used for bags and bottles
   • HIGH DENSITY POLYTHENE
     • Made by heating ethane to lower temperatures
     • Made under low pressure
       • With a catalyst
     • More rigid
       • Used for water tanks and drainpipes