Rheology glass transition measurement

In the comparison of DSC and rheological data, time-scales are crucial. The underlying rheological glass transition Too is thought to be about 50°C below a Tg measured by a slow technique, such as dilatometry [126], and supposedly represents a true Tg at effectively zero frequency or infinite time of measurement. The Donth equation [129] gives a frequency to a DSC measurement based on the width of transition and the rate of the scan. 

Cocero, A.M. and Kokini, J.L. (1991). The study of the glass transition of glutenin using small amplitude oseillatory rheological measurements and differential seanning calorimetry. J. Rheol. 35(2), 257-269. 

Concentration Shift Factor (ac) from Dynamic and Creep Rheological Measurements, Glass Transition Temperature (Tg), WLF Coefficients (C, and C2 [reference temperature Tq = 50 C]), and the Expected Contribution of Tg Change with Concentration to the Concentration Shift Factor... 

It was shown in the preceding section that the glass transition is the result of a relaxation process and that the molecular motion involved is closely related to the motions responsible for viscous flow and mechanical or dielectric relaxation. It follows from this that rheological or dielectric measurements can be used to detect transitions in polymers. In particular the temperature of maximum mechanical or dielectric loss corresponds to the center of a transition range which varies with the frequency of the measurement. 

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