Glass transition determination
The glass transition of a sample corresponds to its transition from a “brittle” solid state to a “soft” molten state often qualified as rubbery. This is a completely reversible state transition that concerns amorphous materials. This transition takes place over a more or less wide temperature range.
It is not strictly speaking a change of physical state, compared to a fusion, boiling, etc.
How to detect a glass transition?
Several physical properties of the sample show a more or less abrupt break during the glass transition of a sample. The mechanical properties are by definition impacted: hardness, etc. The thermal properties are more or less impacted: thermal expansion, thermal capacity, etc.
The temperature monitoring of these parameters makes it possible to observe the rupture in the behavior of the sample, which indicates the presence of the glass transition.