Linear viscoelasticity storage modulus

Other types of linear viscoelastic experiments may be used. Dynamic shear compliance measurements provide the storage and loss compliances J (co) and J"(co). An equation analogous to Eq.(3.12) is available for determining the initial modulus from J"(co) ... 

Figure H3.2.4 Linear viscoelastic region as determined by the strain dependence of G (storage modulus) and G (loss modulus).

It is necessary to state more precisely and to clarify the use of the term nonlinear dynamical behavior of filled rubbers. This property should not be confused with the fact that rubbers are highly non-linear elastic materials under static conditions as seen in the typical stress-strain curves. The use of linear viscoelastic parameters, G and G", to describe the behavior of dynamic amplitude dependent rubbers maybe considered paradoxical in itself, because storage and loss modulus are defined only in terms of linear behavior. 

For deformation within the linear viscoelastic range. Equation 3.76 expresses the generated stress (ao) in terms of an elastic or storage modulus G and a viscous or loss modulus G". 

The storage modulus of HI 8 dispersions in VE resin with low styrene content exhibits high plateau values in the linear viscoelastic regime with G > G" (G omitted for clarity). This is indicative of a viscoelastic solid with percolating gel structure [9]. However, addition of styrene results in a pronounced decrease of the storage modulus. 

The viscoelastic responses of two polymer networks are shown in Fig. 7.29. One is a nearly perfect network (circles) made by end-linking linear chains with two reactive ends. The storage modulus for this network (filled circles) is independent of frequency and much larger than the loss modulus (open circles). For comparison, an imperfect network made by linking a mixture of chains with one and two reactive ends is also shown. 

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