According to the principle of time temperature equivalence, when the relaxation spectrum of viscoelasticity materials measured at different temperatures is translated into the relaxation spectrum at reference temperature, in order to correct the change of materials equilibrium modulus or compliance and density with temperature, it is necessary to move a certain amount in the vertical direction, that is, the longitudinal coordinate of performance logarithm. This shift is called the vertical shift factor.
Organic polymer materials -> Properties of polymer materials and their testing methods