Frequencies for Isothermal-Adiabatic Transitions

For a viscoelastic liquid with G = 10 , the corresponding frequency is about 10 Hz for a soft polymeric solid with G = 10 , 10 Hz for a hard solid with G — 10 , 10 2 Hz. Only in rare cases—possibly for dilute polymer solutions in the megacycle range—would this transition be crossed, since G always increases with frequency. 

Time-Dependent Effects Associated with Heat Flow 

Although the change in the real part of the modulus, G or K accompanying the change from isothermal to adiabatic conditions may be pected to be negligibly small on the basis of the above estimates, it is accompanied by a contribution to G or K associated with the dissipation of energy by heat flow. In the viscoelastic liquids discussed in the present chapter, the effect on G will certainly also be negligibly small compared with contributions from ordinary viscous losses. The phenomenon may appear, however, in E and K for hard solids whose losses due to coordinated molecular motions are very small (Chapters 7 and 8). 

An analysis of viscoelasticity by the methods of irreversible thermodynam-icsi35.i36 shows that under adiabatic conditions the relaxation spectrum lies at slightly shorter times than under isothermal conditions. 

In Appendix B at the end of the book, the experimental methods described in this and the following chapters are summarized with a tabulation of their ranges of applicability. 

---