Video on how I created a walking robot using polycaprolactone. Polycaprolactone is an interesting plastic, allowing you to quickly create prototypes. It melted at 60-65 °C. For melting of polycaprolactone, I used hot water and soldering hot air gun
PCL also has many applications in the hobbyist market (sold under various tradenames, such as "InstaMorph", "Friendly Plastic", "ShapeLock", "PolyMorph", "Plastimake", "Protoplast", "Plaast" etc.). It has physical properties of a very tough, nylon-like plastic that softens to a putty-like consistency at only 60 °C, easily achieved by immersing in hot water. PCL's specific heat and conductivity are low enough that it is not hard to handle by hand at this temperature. This makes it ideal for small-scale modeling, part fabrication, repair of plastic objects, and rapid prototyping where heat resistance is not needed.