Differential Scanning Calorimetry (DSC)

Differential scanning calorimetry (DSC) measures temperatures and heat flows associated with thermal transitions in a material.  In this thermoanalytical technique, the difference in the amount of heat required to increase the temperatures of a sample and a reference are measured as a function of temperature. Both the sample and the reference are maintained at nearly the same temperature throughout the experiment. Generally, the temperature program for a DSC analysis is designed such that the sample holder temperature increases linearly as a function of time.  Only a few milligrams of material are required to run the analysis.

Applications

Common usages of DSC include investigation, selection, comparison, and end-use performance evaluation of materials in research, quality control, and production applications.  DSC is commonly used to measure a variety of properties in both organic and inorganic materials, from metals and simple compounds to polymers and pharmaceuticals. The properties measured include:

  • Glass transitions
  • Phase changes
  • Melting
  • Crystallization
  • Product stability
  • Cure/cure kinetics
  • Oxidative stability
  • Heat capacity and heat of fusion measurements

Principle of Operation

When a sample undergoes a physical transformation, such as a phase transition, more or less heat will need to flow to it than to the reference (typically an empty sample pan) to maintain both at the same temperature. Whether more or less heat must flow to the sample depends on whether the process is exothermic or endothermic.

For example, as a solid sample melts to a liquid, the sample will require more heat than the reference to increase its temperature at the same rate as the reference due to the absorption of heat by the sample as it undergoes the endothermic phase transition from solid to liquid.  Likewise, as a sample undergoes exothermic processes (such as crystallization), the sample requires less heat than the reference to raise the sample temperature at the same rate as the reference.  By observing the difference in heat flow between the sample and reference, differential scanning calorimeters can measure the amount of heat absorbed or released during such transitions. DSC may also be used to observe more-subtle phase changes, such as glass transitions.