Glass transition temperature

What is the Glass Transition Temperature (Tg)?

The Glass Transition Temperature Tg, also known as the glass point, is a point on the temperature scale at which a polymer or glass transitions into a rubbery, viscous state. However, this is not to be confused with the melting point.

For amorphous metals, it is referred to as the glass temperature, and for inorganic non-metallic glasses, it’s termed the transformation temperature.

The glass point is a fixed characteristic, particularly for polymers. A glass transition in plastics is not a true phase transition since only a small portion of the sample changes its state. Specifically, there is a mobility of individual polymer chains relative to each other without transitioning to the melted state.

Since the glass transition cannot be precisely assigned to a specific temperature and depends on the measurement method and conditions, it’s important to adhere to standards in its determination and to be able to precisely control the measurement parameters.

Therefore, the method used for each glass transition temperature must be specified from the measurement methods of Thermal Analysis.

Measurement methods for determining the glass transition temperature

For the determination of the glass transition temperature, the following measurement methods are available: