Rubbery flow region

Knoff,W.F., Hopkins,I.L., Tobolsky,A.V. Studies on the stress relaxation of polystyrenes in the rubbery flow region. II. Macromolecules 4,750-754 (1971). 

Figure 3-23. Comparison of the relaxation behavior of the empirical KWW expression of equation (3-104) with data for PIB in the rubbery flow region. Data NBS PIB see Ferry1 for a table of these data. Copies of the data are also in the CD (PIB-Rel-1. TXT and PIB-Rel-2. TXT).

Figure 4-8. Simulations of master curves and modulus vs. temperature curves for a glassy polymer, (a) The master curves, shown at increments of 5 °C tend to be spaced more widely as the temperature is lowered because of the nature of the WLF relationship used for the temperature dependence [see Figure (4-6)]. (b) Demonstration of the influence of measurement time on the shape of the modulus-temperature curve. As the measurement time increases (by 1-decade increments), the apparent Tg decreases but the sharpness of the transition increases. (Simulation uses Smith empiricism8 for glass transition and the KWW function for the rubbery flow region.)...

Tq, prior to cooling (see Fig. 1), a conclusion which, indeed, is at variance with the classical views, and suggests a structure in the rubbery-rubbery flow region of polystyrene. 

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