Properties of plastics - PowerPoint PPT Presentation

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Properties of plastics

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  1. Properties of plastics You should understand: That monomer used affects a plastic’s properties Plastic’s properties change in different conditions Why plastic is good at it’s job

  2. Plastic • Plastic made up of large chains of monomers • Formed in polymerisation reactions • Chains tangle together to form strong webs • How are the monomers held together in chains?

  3. May the force be with you • Atoms held together with strong chemical bonds • Intermolecular forces • Depend on: • Which monomer • Conditions of polymerisation • Some weak • Some strong

  4. What do we call the forces between polymer chains?

  5. Weak forces • Heat – softens • Cools – hardens • Thermosoftening or thermoplastic

  6. Strong bonds • Heat – doesn’t soften

  7. What do we call a plastic that softens when heated? • What do we call a plastic that does not soften when it is reheated?

  8. Bouncy custard • Carry out a polymerisation reaction using the plastic poly vinyl acetate (PVA Glue) • Custard contains a natural polymer - starch • Borax – acts to form cross links between the 2

  9. Why would a thermosetting plastic be used to produce a kettle? • Polymer A starts to soften at 400oC while polymer B softens at 150oC. Use your knowledge of intermolecular forces to explain why.