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 Polymers Noadswood Science, 2011. Polymers  To be able to describe how plastics and other polymers are made from alkenes Tuesday, April 21, 2015 +

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Presentation on theme: " Polymers Noadswood Science, 2011. Polymers  To be able to describe how plastics and other polymers are made from alkenes Tuesday, April 21, 2015 +"— Presentation transcript:

1  Polymers Noadswood Science, 2011

2 Polymers  To be able to describe how plastics and other polymers are made from alkenes Tuesday, April 21,

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  Alkenes can be used to make polymers  Polymers are very large molecules made when many smaller molecules join together, end-to-end  The smaller molecules are called monomers +

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 alkene double 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 Alkenes  Alkenes can act as monomers because they have a double bond: -  Ethene can polymerise to form poly(ethene) ( polythene )  Propene can polymerise to form poly(propene) ( polypropylene )  Different polymers have different properties, so they have different uses…

10 Polymer Uses PolymerUse PolyethenePlastic bags and bottles PolypropeneCrates and ropes Polychloroethene Water pipes and insulation on electricity cables

11 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

12 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

13 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

14 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

15 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)

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


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