About mechanical models
There are two inadequancies of Maxwell model:
1- Under conditions of creep (const. stress) new tonian flow is observed and this is
not generally true and the creep behavior more complex.
2- The stress relaxation behavior cannot usually be represented by a single exponential
decay term nor decay to zero at infinite time.
From kelvin model:For stress relaxation, the material behaves as an elastic solid and gives in adequate
representation of general V.E. behavior.
For creep Kelvin model represents the creep behavior of polymer to a first
approximation.