Glass transition regions broad

Glass transitions, both in frozen systems and in freeze-dried solids, can be difficult to detect. This may be caused by the small heat capacity change associated with the glass transition, a broad glass transition region, or both. Interpretation is made more uncertain by baseline drift or other noise. In addition, other thermal events at temperatures close to the glass transition, such as enthalpy recovery or crystallization, may disguise the heat capacity... 

Heterogeneous blends with very line scales of segregation may have very broad glass transition regions and good optical clarity. It is a moot point, then, whether such mixtures are compatible. If the components are not truly miscible, the blend is not at equilibrium but the user may not be able to distinguish between a persistent metastable state and true miscibility. 

Slope of the transition region. The slope of the E vs. temperature curve in the glass transition region also varied with M. In accordance to the creep results (discussed later) values of the slope (n), obtained from the dynamic mechanical data (see Figure 3), of the blend samples F-1, F-2, F-3, and F-4 were close to that of the commercial-resin sample E-1. In contrast, the slope of the blend sample F-5 was steeper than that of its commercial counterpart, sample E-5. The broadening of the transition region of the blend samples F-1 to F-4 is attributed to the presence of broad distributions of in them. 

To date, many supposedly miscible polymer pairs [5,6,13,14,42] have been reported in the literature. However, in some cases [13,14], the breadth of the glass transition region, ATg, taken as the difference between the onset and completion temperatures, is quite broad. For some blend systems, ATg values approach 100°C [13,14]. The transition region may also be... 

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