Differential Scanning Calorimetry and Differential Thermal Analysis

Abstract

The importance of thermal analysis methods in thermal and material science has proved awesome. Differential thermal analysis (DTA) and differential scanning calorimetry (DSC) have had a great impact on material science by enabling the measurement of a great number of physical and chemical properties. These techniques have allowed elucidation of endothermic and exothermic processes at temperatures ranging from very low (−120°C) to high (DSC 600°C and DTA 1800°C). 1–6 Some of the physical properties measured by these thermal analytical methods include melting transitions, crystallization temperatures, enthalpy of fusion and crystallization, specific heat capacity, liquid crystal transitions, vaporization, sublimation, solid–solid transitions, thermal conductivity and the glass transition temperature. 7–14 Chemical properties monitored by DSC and DTA are dehydration, decomposition, oxidative reactions, solid state reactions, chemisorption, combustion, polymerization, curing and catalyzed reactions. 15–19 In DTA, the temperature difference between the substance and a reference material is measured as a function of temperature, while the substance and reference material are subjected to a controlled temperature program. 20 In DSC, the difference in energy input into a substance and a reference material is measured as a function of temperature, while the substance and reference material are subjected to a controlled temperature program. 21 Two modes, power compensation DSC and heat flux DSC, can be distinguished, depending on which method of measurement is used. 22,23 The following is a review of DSC and DTA and their role in thermal science. The root of thermal analysis is the determination of heat and temperature. Heat is a macroscopic quantity and has its origin in molecular motion. 24 DTA measures the temperature difference between a sensitive reactive material and an inert reference as a function of time and temperature. DTA measurements provide information about transition temperatures as well as kinetic time‐based phenomena and thermodynamic properties. DSC is a step above DTA in that it measures quantitative heats of reaction and transitions. Both thermal methods can differentiate first order thermodynamic changes like fusion, and second order thermodynamic changes like a glass transition temperature, T g . This chapter will focus mainly on fundamentals, instrumentation and applications of DSC.