Editing Polymer Milk Jug (section)

== Why This Works ==

Polymers have become an essential part of our lives. We encounter polymers throughout our entire day, from the food we eat to the clothes we wear and the toys we play with. ''Polymers'' are strings of molecules bonded together in extremely long repeating chains. These chains connect end to end, and can stretch, bend or warp to resist breaking or separating. This demonstration focuses on what we call ''Thermoplastics'', which are plastic polymers that can be altered by heating them.

Our milk jug is a plastic, and plastics are usually numbered from #1 to #7. There are seven types of plastics, and each one has different properties to them. Each type of plastic can be recycled, but when they are recycled they might be transformed from one type to another, depending on what type is needed. Our container is a #2 plastic, which is high density polyethylene or HDPE. HDPE has a rigid polymer, which is why it is stiff and doesn't bend easily. When we heat the wall of the container, we are making the polymer melt, making it less stiff. By blowing air into the container, we then are stretching out the melted polymer, which will stretch as far as it can to resist breaking. Polymers don't like to separate, so the wall will stretch out a LOT before it cools down and re-solidifies. Once cooled, it is now a #4 plastic, a low density polyethylene or LDPE!