The Amazing Mr. Fantastic is a Thermoplastic
Thermoplastic polymers become pliable or mold-able when raised to a rather high, but very specific temperature and solidify upon cooling. The forces holding the molecules together in a thermoplastic, the inter-molecular bonds, weaken when the right amount of heat is applied. The molecules of the plastic stretch further away from each other, like beads on an elastic charm bracelet or the metallic links on an elastic watchband, making the material softer and more pliable. Add enough heat and the material melts into a liquid that can be used in injection-molding, compression molding, calendaring, and extrusion.