Silly Putty is a
toy based on
silicone polymers that have unusual physical properties. It bounces, but breaks when given a sharp blow and can also flow like a liquid. It contains a
viscoelastic liquid silicone, a type of
non-Newtonian fluid, which makes it act as a viscous liquid over a long time period but as an elastic solid over a short time period. It was originally created during research into potential
rubber substitutes for use by the
United States in
World War II.