Polycaprolactone(PCL) also known as Polymorph, is a soft material just like glue gun sticks, and it has a low melting point around 60 degrees Celcius.

It can easily be melted in a bowl of hot water and reshaped in new forms. It's is not as strong but still it is very useful as early prototype material since it is quick to recycle with a low amount of energy.

Polymorph