An addition polymer is a polymer which is formed by an addition reaction – could probably guess that by its name!

In this reaction many monomers join together under specific conditions such as heat, pressure and in some instances the presence of a catalyst.

Addition occurs when there is a reaction between double or triple bonds in which units of atoms are added, which in turn changes the double bonds to single bonds.

Addition polymerisation is when an alkene double bond opens in order to add to another alkene molecule and this process is then repeated – the term chain reaction comes to mind.

Also it’s easy to see when addition polymerisation has taken place because of the name of an element.

You’d like some examples? No problem.

Ethene makes polyethene, propene makes polypropene, phenylethene makes polyphenylethene – do I have to go on?

Earlier we mentioned the conditions needed to form a polymer, so sticking with our example: To make high density polyethene you must have a reaction at room temperature and pressure with a ziegler-natta catalyst. (A polymer catalyst).

High density poly(ethene)s are more rigid and have a higher melting point, making them more useful for, for example bleach. Low density ones are more flexible and light, making them useful for plastic bags and bottles.
Now for the downside to polymers. Most plastics are made from polymers and they are non-biodegradable.

The physical property of multiple polymers varies depending on structure, but almost all are non-biodegradable. They cannot be broken down by microbes, and stay in the environment for millions of years.

However, if we use less plastic in day to day life, and ensure that we use thermoplastics; those that can be melted and remolded, we can ensure that plastics do less damage to the environment than they are currently. This is known as mechanical recycling.