Viscoelasticity

Viscoelasticity is a material property that combines both viscous and elastic characteristics. Many materials have such viscoelastic properties. Especially materials that consist of large molecules show viscoelastic properties. Polymers are viscoelastic because their macromolecules can make temporary entanglements with neighbouring molecules which causes elastic properties. After some time these entanglements will disappear again and the macromolecules will flow into other positions where new entanglements will be made (viscous properties).

A viscoelastic material will show elastic properties on short time scales and viscous properties on long time scales. These materials exhibit behavior that depends on the time and rate of applied forces, allowing them to both store and dissipate energy.

Viscoelasticity has been studied since the nineteenth century by researchers such as James Clerk Maxwell, Ludwig Boltzmann, and Lord Kelvin.

Several models are available for the mathematical description of the viscoelastic properties of a substance:

The viscoelastic properties of polymers are highly temperature dependent. From low to high temperature the material can be in the glass phase, rubber phase or the melt phase. These phases have a very strong effect on the mechanical and viscous properties of the polymers.

Typical viscoelastic properties are:

The viscoelasticity properties are measured with various techniques, such as tensile testing, dynamic mechanical analysis, shear rheometry and extensional rheometry.

In the nineteenth century, physicists such as James Clerk Maxwell, Ludwig Boltzmann, and Lord Kelvin researched and experimented with creep and recovery of glasses, metals, and rubbers. Viscoelasticity was further examined in the late twentieth century when synthetic polymers were engineered and used in a variety of applications.