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Crowe2008

Addition polymerization of alkenes. Connector - Draw the major addition products for the reactions between i) Br 2 & ii) HBr with: propene, but-1-ene, but-2-ene, and 2-methylpropene.

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Crowe2008

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  1. Addition polymerization of alkenes Connector - Draw the major addition products for the reactions between i) Br2 & ii) HBr with: propene, but-1-ene, but-2-ene, and 2-methylpropene 3g. describe the addition polymerization of alkenes and identify the repeat unit given the monomer, and vice versa Crowe2008

  2. Br H Br Br H Br Br Br H H H H H H H H H H C – C C C – C C C C C C C C C C H H H H H H H H H H H H H H H H H H Markovnikov addition Markovnikov addition

  3. Br H H Br Br Br Br Br H H H H H H H H C C C C C C C C C C C C CH3 CH3 H H H H H H CH3 CH3 H H H H H H Markovnikov addition

  4. Ethene This molecule is called POLYETHENE, and the process that made it is called POLYMERISATION Monomers and Polymers Ethene is called a MONOMER because it is just one small molecule. We can use ethene to make plastics… Step 1: Break the double bond Step 2: Add lots of the molecules together:

  5. Manufacture of addition polymers. • An addition reaction is one in which two or more molecules join together to give a single product. During the polymerisation of ethene, thousands of ethene molecules join together to make poly(ethene) - commonly called polythene. • The number of molecules joining up is very variable, but is in the region of 2000 to 20000. Conditions • Temperature: about 200°C • Pressure: about 2000 atmospheres • Initiator: a small amount of oxygen as an impurity

  6. H H H H H H H H H H C C C C C C C H C C C H H H H H H H H H H poly(e)thene Pressure high temperature catalyst n n ethene Another way of drawing it… And lots more.. 1 2 3 4 5 thousands This is called addition polymerisation and is written as: n = a large number

  7. n C C n CH3 H n Poly(tetrafluoroethane) or PTFE tetrafluoroethene H H Draw the equations for the polymerisation of the following alkenes and name the polymer: propene

  8. Poly(propene) n n propene n n Poly(tetrafluoroethene) or PTFE tetrafluoroethene CH3

  9. You may be asked to show polymerisation using three or more monomer units. e.g. Draw a similar process for propene and chloroethene

  10. Thermosoftening polymersor thermoplastics: These soften when heated and can be remoulded into new shapes weak intermolecular forces –these let the chains slide past each other

  11. What are thermosetting plastics? Some polymer chains cannot slide past each other. strong intermolecular forces(cross-links) –these hold the chains firmly in place Plastics made of these polymers cannot be stretched, are rigid and have a high melting point. They are called thermosetting plastics (or ‘thermosets’).

  12. Homework - Research the problems and solutions wrst the use of polymers. • You should include the following key areas: • Energy • costs • sources • Resources used • Disposal problems • biodegradable polymers • Carbon footprint • Recycling/reusing

  13. Use the above data to compare the properties of PLA with polystyrene and PVC. Produce graphs to show the tensile strength, elastic modulus and tear strength as both hard sheets and soft films. How does PLA compare with conventional polymers?

  14. How does PLA compare with conventional polymers? hard sheets soft films

  15. Life cycle analysis

  16. Life cycle analyses of three different materials for gas pipes • Present the information in the form of a bar chart so that the environmental features may be compared. • Suggest why the scientists may have been surprised by their findings.

  17. Life cycle analyses of three different materials for gas pipes • Suggest why the scientists may have been surprised by their findings.

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