Time dependence of Poisson’s ratio for PVC at 75◦C, assuming viscoelastic shear response and elastic hydrostatic response.
This function is plotted in Fig. 18. The Poisson’s ratio is seen to rise from a glassy value of 0.25 to a rubbery value of 0.5 as the material moves from the glassy to the rubbery regime over time. Note that the time constant of 120 s in the above expression is not the same as the relaxation time τ for the pure shear response.