Polymers Made From Alkenes

Alkenes Can Be Used To Make Polymers

Alkenes can do a really nifty thing called polymerisation. What this entails is joining lots of small alkene molecules, called monomers together to form long chains of molecules called polymers.

If you take the ethene for example you can join lots of its molecules together to for poly(ethene)…..or polythene as it is more usually called.

ethene to polythene

Properties Of Polymers

Different polymers have different properties – for example polypropylene tends to be stuffer than polythene. An particular polymer’s properties also depend on the temperature and pressure at the time of polymerisation. For example is polythene was made at 200 degrees and 2000 atmospheres pressure it will be flexible and not too dense. If it was made at 60 degrees with only a few atmospheres pressure and a catalyst present it will be rigid and very dense.

This means they can have a few different uses:

  • Polythene is light so can be used to make plastic bags.
  • LYCRA is made from polymer fibres!
  • New packaging materials
  • Waterproof coatings for fabrics
  • Dental polymers
  • Wound dressings
  • Hydrogels
  • Smart materials (including shape memory polymers….the sort that are in those clever mattresses).

Polymers Are Not Biodegradable

This means they won’t be broken down by microorganisms…which can be a problem for the environment because in landfills they just hang around for years and years.

The best solution is to recycle them. However, plastic bags are now sometimes being made from polymers and cornstarch so that they break down more easily.

At the moment plastics like polythene are much cheaper than metal, but as crude oil runs out they might get more expensive. We might have to make a balance between fuel and plastics in the future as we can’t go on producing both indefinitely.