5.1 Materials undergo an increase in molecular mobility at the glass transition seen as a sigmoidal step increase in the heat capacity. This mobility increase may lead to kinetic events such as enthalpic recovery, chemical reaction or crystallization at temperatures near the glass transition. The heat flow associated with the kinetic events may interfere with the determination of the glass transition.

5.2 The glass transition is observed in differential scanning calorimetry as a sigmoidal or step change in specific heat capacity.

5.3 MTDSC provides a test method for the separation of the heat flow due to heat capacity and that associated with kinetic events making it possible to determine the glass transition in the presence of interfering kinetic event.

5.4 These test methods are useful in research and development, quality assurance and control and specification acceptance.

5.5 Other methods for assigning the glass transition temperature include differential scanning calorimetry (Test Method E1356), thermomechanical analysis (Test Method E1545) and dynamic mechanical analysis (Test Method E1640).