Thermal Analysis Fun Facts

1st : Why doesn't the glass transition phenomenon show a peak?

In DSC measurements, melting appears as an endothermic peak, crystallization as an exothermic peak, and crystal transitions may show either endothermic or exothermic peaks. While we typically observe these endothermic and exothermic peaks, the glass transition is unique in that it appears not as a peak, but as a stepwise (shifted) behavior toward the endothermic direction of the baseline.

This is because the glass transition is not a change accompanied by reaction energy, such as an endothermic or exothermic reaction, but rather a change in which the specific heat capacity increases abruptly.

In some cases, due to enthalpy relaxation, an endothermic peak may be observed simultaneously with the baseline shift associated with the glass transition.