Polymers

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Addition Polymers

  • Polymer: a large molecule made up of many repeating units or monomers


  • Addition polymers can be formed by repeated addition reactions between unsaturated hydrocarbons, such as alkenes

 

  • Unlike in condensation polymerisation, the polymer itself  is the only product formed during addition polymerisation
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Uses of Addition Polymers

Monomer                          Polymer                            Repeating Unit                              Uses

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Condensation Polymers

  • Condensation polymers are formed by a condensation reaction between two different functional groups.

 

  • For example, polypeptides are formed from amino acids, which each contain an amine group and a carboxylic acid group

 

  • Polyesters are fromed from a dicarboxylic acid and a diol: a compound containing two hydroxyl groups
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Biodegradability

  • Poly(alkenes) are chemically inert and are therefore non-biodegradable
  •  Poly(alkenes) can become more biodegradable if, for example, starch is incorporated into poly(ethene) used for carrier bags. Starch is hydrolysed by microorganisms, which breaks down the carrier bag
  • Polyesters and polyamides are biodegradable. Methyl ethanoate can be hydrolysed to produce methanol and ethanoic acid, for example
  • Polyesters are readily hydrolysed by strong alkalis, and polyamides are readily hydrolysed by strong acids. Certain enzymes can also be used for hydrolysis
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Recycling Polymers

Advantages

  • Protection of useful hydrocarbons for the future
  • Reduces landfill

Disadvantages

  • Difficult and expensive; polymers are often mixed with paints or dyes and must be separated
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Disposing of Polymers

Landfill


  • Limited amount of land available
  • Landfill sites fill up very quickly, especially when non-biodegradable polymers are disposed of

Incineration

  • Carbon dioxide, a greenhouse gas, is produced
  • Toxic gases can be produced unless polymers are incinerated at very high temperatures
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