Thermosetting Plastics  

Plastics come in two broad types. Thermoplastics, which are the types often found in schools and can be easily recycled. Thermosetting plastics which cannot be easily recycled rely on mixing chemicals together to create a new substance. A good example of this would be epoxy resin glue (such as Araldite) which does not harden until the two tubes are mixed together. For more detailed information see the animation below.

Epoxy resin

Just thought I'd let you see some epoxy resin glue (it's a thermosetting plastic you know), mix the tubes together and it goes hard in about 10 minutes. It glues almost anything. Why do we have all the different types of glue I hear you ask, because if you were just sticking wood you would use PVA 'cause it is a lot cheaper. (PVA is a type of plastic you know it stands for Polyvinyl Acetate).