Polymers

The most useful thing to do with alkenes is to make them into polymers like poly(ethene) and poly(propene) This is called polymerisation.

For example, many small ethene molecules (monomers) can be joined up to produce long molecules (polymers) like poly(ethene) or polythene.

e.g:      H H          (H H)  n  C=C   >    (C-C)      H  H         (H H) n     ethene        Poly(ethene)In the same way, if you join lots of propene molecules together, you've got poly(propene)

Different polymers have many different uses:Light stretchable polymers can be used to make plastic bags.Waterproof coatings for fabrics are made from polymersNew biodegradable packaging materials made from polymers and cornstarch are being produced.

However, most polymers aren't biodegradable - they're not broken down by decomposers so they don't rot. This means that it is difficult to get rid of them and they lead to waste disposal. Although, plastic bags are now being made from cornstarch so that they break down more easily. Other biodegradable plastics made from cornstarch are being developed.

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