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Differential Scanning Calorimetry (DSC)
Differential Scanning Calorimetry, DSC, is a thermo analytical technique in which the difference in the amount of heat required to increase the temperature of a sample and reference are measured as a function of temperature. Both the sample and 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.
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 it will require more heat flowing to the sample to increase its temperature at the same rate as the reference. This is due to the absorption of heat by the sample as it undergoes the endothermic phase transition from solid to liquid. Likewise, as the sample undergoes exothermic processes (such as crystallization) less heat is required to raise the sample temperature. By observing the difference in heat flow between the sample and reference, differential scanning calorimeters are able to 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.
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
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