Question

The Deborah number (De) is defined as follows:
De = relaxation time of the material / time scale of the process or experiment
When De<<1, the material may be described as being “liquid-like” in its response, and when
De>>1, the material may be described as “solid-like”. At intermediate values, the material may
be described as being viscoelastic, having a dual liquid (visco-) and solid (elastic) behavior.
(a) From this definition explain why at room temperature water and window glass are not
viscoelastic while a compound like silly putty is.
(b) How does the phenomenon of the glass transition temperature relate to viscoelasticity?
(c) Please give an example of a viscoelastic phenomenon that may occur during melt processing
of a polymer.

Answer 1