Thermosetting and Thermosoftening polymers

• HD polymers are...

  Hard
• LD polymers are...

  soft
• HD and LD polymers are made from the same monomer but in different conditions, true or false?


  true
• What conditions can you change?

  temperature, catalyst and pressure
• Do T.soft melt in heat. Why/Why not?

  yesthey have weak cross-links
• Do T.sett melt in heat. Why/Why not?

  nostrong cross-links
• Low density poly(ethene), LDPE

  Flexible, unreactive, can be made into films

  Most carrier bags, bubble wrap
• High density poly(ethene), HDPE

  Strong, flexible, resists shattering, resists chemical attack

  Plastic bottles, pipes, buckets
• Thermosoftening plastics melt when they are heated. Most plastics that we come across in everyday life are thermosoftening plastics. This means that they can be recycled, which involves melting them before making a new product.
• Thermosoftening plastics do not have covalent bonds between neighbouring polymer molecules, so the molecules can move over each other when heated and the plastic melts.
• Thermosetting plastics do not melt when heated. They tend to char and burn when heated, but they are resistant to much higher temperatures than thermosoftening plastics. They are used to make electrical plugs, which must not melt, even if there is a malfunction and the wiring inside gets hot.