【国外标准】 Standard Test Methods for Assignment of the Glass Transition Temperature by Modulated Temperature Differential Scanning Calorimetry

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).1.1 These test methods describe the assignment of the glass transition temperature of materials using modulated temperature differential scanning calorimetry (MTDSC) over the temperature range from –120 °C to +600 °C. The temperature range may be extended depending upon the instrumentation used.1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.