Polymers

• Polymers are long-chained molecules with large molecular masses that are made from short-chained molecules called monomers which are added together via addition polymerisation.
• Monomers involved in addition polymerisation are always alkenes.
• The alkenes in addition polymerisation add together across the C=C bond where the pi bond breaks, producing saturated long chain molecules.
• A repeat unit is the smallest group atoms that when connected one after the other make up the polymer chain
• The repeat unit is represented by square units in the displayed formula.
• Polymers are unreactive.
• Polymers are not biodegradable.
• Recycling reduces the amount of waste going to landfill and reduces the amount of raw materials needed to make new products, thereby reducing the environmental impact.
• PVC Recycling:

  • high chlorine content makes the disposal and recycling hazardous
  • when burnt, HCl is released
  • new tech uses solvent to dissolve, then recovered by precipitation and the solvent is used again
• Feed stock recycling:

  • chemical and thermal processes that reclaim monomers, gases, or oil from waste polymers, then used for the production of new polymers.
• Biodegradable polymers are broken down by microorganisms (bacteria).
• Photodegradable polymers are broken down by light.
• Bio/photodegradable polymers are renewable and sustainable. This protects the environment and conserves valuable oil reserves.
• Biodegradable polymers are broken down by microorganisms into water, carbon dioxide, and biological compounds. They are usually made from starch/cellulose.
• Recycling polymers is a time-consuming process as they have to be sorted into the different categories.
• You can burn (combust) polymers under controlled conditions to produce heat energy which can then be used to generate electricity.
• Since they have a large amount of energy stored within the polymer chains, polymers can be incinerated. This process can then be used to boil water and use the water vapour to turn turbines inside a power station, in a similar fashion to coal-fired power stations.
• The major benefit of feedstock recycling, compared to other methods of polymer disposal, is that it works with unsorted and unwashed polymers.
• Photodegradable polymers contain bonds that are weakened by absorbing light / visible radiation

  This starts the breakdown of the polymer. A lot of photodegradable polymers are oil-based. In certain cases, an additive that absorbs light is mixed into the polymer to promote degradation
• State one use of (poly)chloroethene (PVC).

  Window frames.
• State one use of (poly)propene.

  Carpet fibres.
• State 2 disadvantages of PVC and polypropylene.

  -Non-biodegradable

  -Toxic gases released when burned
• Describe how scientists are working to overcome the problems with polymers.

  -Develop bio-degradable polymers

  -Burn as a fuel source for energy

  -Sort and remould into new objects

  -Sort and crack into monomers to be used as an organic feedstock to make other chemicals or new plastics.
• State one particular problem with disposal of poly(2-chloropropene) by combustion.

  Forms hydrochloric acid, which is toxic/hazardous.
• State two methods of disposing of polymers that can be beneficial to the environment.

  -Combustion for energy production

  -Production of plastics