Nov 05 2008
What is ‘Terminal relaxation time’ in rheology?
LI J asked:
I don’t know what the term ‘Terminal relaxation time ‘ means.
I hope someone can help me. Many thanks.
I don’t know what the term ‘Terminal relaxation time ‘ means.
I hope someone can help me. Many thanks.
One Response to “What is ‘Terminal relaxation time’ in rheology?”
Viscoelastic materials behave differently to applied stresses depending on the time scale over which the stress is applied. Over short time scales the material will have a high elastic modulus, but over longer time scales the modulus eventually drops off to zero.
If the a polymer has a high enough molecular weight (above the MW of entanglement) the elastic modulus will drop quickly and then level off to a plato modulus. Eventually the polymer transitions through this region and the elastic modulus drops to essentially zero. The terminal relaxation time is the time at which the rubbery plato region ends.
A typical relaxation curve will look like the profile of a boot. The plato region is the foot of the boot and the terminal relaxation time is the toe.