Glass transition estimation from melting point

The Cp curve of the terpolymer (upper curve Figure 9) is more complex. It rises smoothly from — 120° to — 40°C but above — 34°C increases abruptly, and a broad endothermic peak, typical of fusion of polymer crystals, occurs between 50° and 77°C. We attribute the initial discontinuity in Cp at — 34°C to the onset of glass transition and the subsequent increase in Cp to melting. The point of inception of melting of terpolymer crystals can be estimated by extrapolating the Cp curve... 

In this expression, r is in Pas, T is the temperature in K, Tg is the end point of the glass transition, and A(l/Tg) is equal to (1/Tg-l/Tg). In most cases, this expression will yield a calculated value of the viscosity which is within one order of magnitude or less of the true viscosity, as is shown in Figure 12.8 for a NIST standard glass. The simplicity of this method provides a very useful tool for estimating the viscosity of an unknown melt from a single DSC measurement. 

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