How to Perform DSC Measurements

Before carrying out a DSC experiment, the operator needs to select several parameters. It should be emphasized that there are no optimum parameters 

Before loading the sample into the DSC instrument, it has to be encapsulated into DSC pans. The pans used for polymers are usually made of high-purity aluminum. For high-temperature measurements of inorganic samples, often copper, gold, silver, or platinum (sometimes graphite and sapphire) pans are used, because aluminum melts at 660 °C, and alloys with the material of the sample holder. An overview of the most frequently used DSC pans is given in Section 2.3. 

For everyday DSC measurements on polymers, the usual standard aluminum pans should be used (Figs. 2.7 and 2.8). These pans should never be used without a lid, because the major function of the lid is to push down the sample to the bottom of the pan, ensuring good thermal contact. The disadvantage of standard pans is that modern crimpers tightly fold down the pan edge on the lid, so when it is desirable to evaporate some solvent from the sample, the solvent may be slow to leave the pan. In these cases, it is better to punch out lids from aluminum mesh as shown in Figs. 2.7 and 2.8. 

Hermetically sealed pans should be used for volatile (or liquid) samples. After the liquid sample is placed on the bottom of the DSC pan, it is covered with a lid, and the edges of the bottom and the lid are cold-welded together with a small instrument called a crimper. The process itself is called crimping. In addition to measurements on low-molecular-mass liquids, these sample pans should be used for liquid samples such as unreacted thermosets and when the sample contains volatile components such as residual solvent or low-mass additives whose evaporation one wishes to suppress (these pans are also used for polymers that can release degradation products). Evaporation of these materials is endothermic and may interfere with exothermic events such as 

High-pressure DSC capsules are used in cases when the pressure in the DSC pan may reach 20 MPa (-200 atm) as a result of heating to high temperatures, and it is undesirable to release some solvent or gases of decomposition into the DSC cell. These pans are rarely used in measurements on polymeric samples. 

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