When the weight is removed, the material will return to its original shape. Because of their unique time dependant property, they have been termed viscoelastic. The modulus is independent of strain but dependant upon time. At these small strains, the material is considered linear viscoelastic. 3 Engineers have long exploited the viscoelastic properties of polymers.
Plastics have very good dampening properties.
The noise reductions are significant and the material costs and labor involved for fabrication are minimal. The dynamic properties of plastics are also of interest. For a linear viscoelastic material, the stress response is also sinusoidal but out of phase with the strain. A plot of equations 4 and 5 is presented below. 1 Polyurethane is highly amorphous elastomer and is used as an alternate to rubber in many engineering applications.