Voici le plastique polymorphe !!
"PCL also has many applications in the hobbyist market (sold under various tradenames, such as "InstaMorph", "Plasty Craft", "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."