Chapter 2 - Temperature-modulated DSC (TMDSC)

Abstract

Temperature-modulated DSC (TMDSC) was introduced to resolve overlapping transitions. It differs from the standard DSC in that it applies two simultaneous heating rates to the sample. The linear or average heating rate provides the same information (total heat flow rate) as standard DSC, while the modulated heating rate is used to determine the fraction of the total heat flow rate that responds to a changing heating rate. This fraction of the total heat flow that is frequency dependent is called reversing heat flow or heat capacity component of the total heat flow. This chapter reports the definition, theory, principles, and operating conditions (e.g., sample size, modulation period, measuring transitions, and modulation amplitude) of TMDSC method and its applications, especially its use for studying the thermodynamic properties of polymers and pharmaceuticals. We provided detailed comparison between DSC and TMDSC methods to show the advantages of TMDSC over the traditional DSC in resolving interfering thermal events, providing the best sensitivity for otherwise weak transitions, and improving the precision of heat capacity measurements. Moreover, we talked in this chapter about all techniques of TMDSC, including the isothermal step (IsoStep) method, the alternating DSC (ADSC) method, and, finally, the most advanced TOPEM method and their unique applications such as studying the thermal response of samples at different frequencies.