ASTM E1356 Glass Transition Temperatures by Differential Scanning Calorimetry
Many substances take on a solid-like amorphous state when observed at low temperatures. Compounds such as oils and polymeric materials can change from this brittle, glass-like state to a more flexible, rubber-like state as they are allowed to warm and pass through their glass transition temperature. This is an exothermic transition that can be detected by differential scanning calorimetry (DSC). This test determines the glass transition temperature of amorphous materials.
The sample is placed in the DSC, cooled below its glass transition temperature and then slowly warmed. The DSC monitors the temperature flow until the exotherm is observed. This is reported as the glass transition temperature.