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Polymers

Polymers. Noadswood Science, 2012. Polymers. To know how the structure of polymers affects their properties. +. Plastics. What are plastics – how are these made, and why are they so useful?

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Polymers

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  1. Polymers Noadswood Science, 2012

  2. Polymers • To know how the structure of polymers affects their properties +

  3. Plastics • What are plastics – how are these made, and why are they so useful? • Plastics are polymers (huge molecules which are made up of lots of smaller molecules (monomers) which have been joined together) • Different types of plastics can be made by using different monomers – these plastics can have very different properties… *Plastic surgery is not connected with polymers: the name derives from the Greek plastikos meaning to mold /shape

  4. Nylon • Nylon was the first commercially successful synthetic polymer – a thermoplastic (softens when heated) silky material originally used in toothbrushes and later as tights… • It is formed when a combination of smaller molecules join together: two solutions with different densities are layered • A film of nylon appears instantly where the two layers meet

  5. Monomer  Polymer • Polymers are very large molecules made when many smaller molecules (monomers) join together, end-to-end Many monomer molecules  a polymer molecule +

  6. Monomer  Polymer • Polymer: Poly(ethene) - polythene • Many ethene monomers can join end-to-end to make poly(ethene) or polythene • Initially the C=C double bond of the ethene must be broken, and then the molecules can be added together…

  7. Monomer  Polymer Initially the alkenedouble bond (C=C) is broken Monomers are joined together Polymer formed

  8. Monomer  Polymer • Polymer: Poly(chloroethene) – PVC • Many chloroethene monomers can join end-to-end to make poly(chloroethene) or PVC…

  9. Polymers • Different polymers have different properties (melting point, density, strength etc…), so they have different uses… • Their properties are different as the chain length and the amount of branching in a polymer can vary (affecting the strength of forces between the chains)

  10. Polymers • Kevlar (poly-paraphenylene terephthalamide) is a polymer – very lightweight but extremely high tensile strength

  11. Polymers • Modern rock climbing ropes / foam inner layers of cycle helmets / tennis racquets are all made of polymers…

  12. Polymer Uses

  13. Slime • Complete the slime experiment: - • Add a few drops of the borax solution to a warm solution of PVA glue (you can add some food colouring if you wish to enhance the appearance) • Stir well for at least 2 minutes… • *The glue becomes slimy because the borax makes the long polymer chains in the glue link together, forming a jelly-like substance

  14. Properties • Different polymers can be made by using different monomers – these polymers can have very different properties… • Polymers have properties that depend on the chemicals they are made from, and the conditions in which they are made – modern polymers have many uses, including: - • Waterproof coatings • Fillings for teeth • Dressings for cuts • Hydrogels for making soft contact lenses and disposable nappy liners • Shape memory polymers for shrink-wrap packaging

  15. Plasticisers & Slime • Plasticisers are substances that let the polymer molecules slide over each other more easily making the polymer softer and more flexible • Poly(chloroethene) or PVC is a hard polymer: - • Unplasticised PVC (uPVC) is used to make pipes and window frames • PVC with plasticisers is soft and flexible and is used for floor coverings, raincoats and car dashboards

  16. Plasticisers & Slime • Poly(ethenol) is a polymer that dissolves in water to make slime: the viscosity of the slime can be changed to make it thick or runny by varying the amount of water

  17. Thermosoftening & Thermosetting • Polymers can fall into two categories: - • Thermosoftening – can be heated and shaped many times • Thermosetting – can only be heated and shaped once • Thermosetting polymers have their chains cross linked by covalent bonds – the polymer is originally placed into a mould and heated causing cross links to form (further heat will not cause the polymer to soften or change shape)

  18. Thermosoftening & Thermosetting • Thermosoftening (top) and thermosetting (bottom) showing the cross link bonds which causes it to hold it’s shape

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