Thermal Analysis Fun Facts

4th : What should you do when the glass transition cannot be identified by DSC?

DSC is the most commonly used technique for determining the glass transition temperature. However, because the glass transition phenomenon appears as a baseline shift toward the endothermic, you may sometimes feel that it is “hard to see,” “difficult to figure out,” or wonder, “Is this really the glass transition?”

For highly crystalline samples, one effective approach is to heat the sample above its melting point, then rapidly cool (quench) it to increase the proportion of amorphous material and remeasure. Another effective method is to observe the changes in softening and expansion rates using TMA.

In TMA measurements, the glass transition phenomenon appears as a change in which softening or the thermal expansion rate increases sharply. By focusing on these temperature ranges and carefully reexamining the DSC data, you may be able to identify the corresponding baseline shift due to the glass transition.

When measuring by TMA, samples in the form of films or blocks can be measured directly. Even for powder samples, the sample can be placed in an aluminum pan, covered with an aluminum lid, and then set up on the TMA for measurement.