Transition region from glasslike

The introduction forms Chapter 1 of this survey. Chapter 2 deals briefly with various approaches to the description of the concentration dependence of the viscosity of disperse systems, including the transition region from fluid to solid-like systems. Chapter 3 describes viscosity from the standpoint of the free volume theory and the specific features of the transition from mobile to glasslike systems. Chapter 4 presents the concept of the free volume of disperse systems developed by us as well as the results of experiments illustrating it Chapter 5 contains the pertinent generalizations and conclusions. 

For a more extensive comparison of polymers, two quantities have been somewhat arbitrarily selected as gauges of the location of the transition zone the frequency where <7 = 10 dynes/cm, a value intermediate between those characteristic of the rubberlike and glasslike states (corresponding approximately to the reciprocal time where <7(r) = 0.8 X 10 dynes/cm since tan 6 a 1 in this region—cf. equation 13 of Chapter 10), and the frequency where tan 5 is a maximum. These are summarized for the polymers of Figs. 12-1 and 12-2 and a number of others from data taken from the literature"" at several different temperatures in Table 12-1. For... 

Even without an analytical expression to describe the shape of H, it is clear that increasing steepness of H in the transition zone as portrayed in Fig. 12-11 will be accompanied by a compression of the transition from rubberlike to glasslike consistency into a narrower region of logarithmic time scale. Plots of both transient and dynamic moduli and compliances, as exemplified in Chapter 2, rise and fall with steeper slopes. Perhaps the most sensitive index of the sharpness of the transition is the loss tangent, which is plotted in Fig. 12-12 for several prototypes the polyurethane rubber, poly( -octyl methacrylate), poly(vinyl acetate), and Hevea rubber. Here the frequency scale has been arbitrarily selected to make the maxima coincide. The sharpness in the loss maximum correlates with the slope of H in the transition zone. The shape emphasizes the failure of the modified Rouse theory to provide a detailed description of the properties in the transition zone, since it predicts tan 5 = 1 independent of frequency in this region. The drop in tan 5 at high... 

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