Viscoelastic Behavior in Bulk Voluminal Deformation

UNEAR VISCOELASTIC BEHAVIOR IN BULK (VOLUMINAL) DEFORMATION 

As an example of bulk viscoelastic behavior, data for a poly(vinyl acetate) of moderately high molecular weight are shown in Fig. 2-9. Measurements by McKinney and Belcher of the storage and loss bulk compliance B and B at various temperatures and pressures are plotted after reduction to a reference temperature and pressure of 50°C and 1 atm respectively (see Chapter 11). The complex bulk compliance is formally analogous to the complex shear compliance, but the two functions present several marked contrasts. 

Viscoelastic behavior in simple extension or in bulk longitudinal deformation will in general combine the features of shear and bulk viscoelasticity, since the moduli E t) and M t) depend on both (7(0 and K t), as shown by equations 51 and 58 of Chapter 1 ( and analogous relations for E and M ). However, as already pointed out, shear effects predominate in E(t) and E. and bulk effects predominate 

Storage and loss bulk compliance plotted logarithmically against frequency, for a poly(vinyl acetate) reduced to 50°C and I atm, as described in text.  

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