Setting Up a DSC Cyclic ProcedureSetting Up a DSC Cyclic Procedure
DSC Cyclic experiments are used to assess changes in the material as it is exposed to a series of heating/cooling cycles. Multiphase materials (e.g., emulsifiers) often change internally (become less stable) during thermal cycling.
If you want to set up a DSC cyclic procedure, you can choose one of two techniques—the DSC Wizard or the Experimental View - Procedure Page. See the instructions below for each technique.
When you perform a DSC Cyclic experiment, four parameters need to be chosen:
Start and Final Temperatures: The actual starting and final temperatures chosen for a specific experiment must be within the usable temperature of the DSC/cooling accessory combination that you are using. The RCS and LNCS can be used for cyclic experiments spanning subambient to elevated temperatures. The FACS can be used for cyclic experiments from 50 to 500°C. The Quench Cooler cannot be used for cyclic experiments. These temperatures should bracket the region where sample transitions are expected to occur and they should be far enough below or above the transitions to establish a stable baseline.
When selecting the final temperature you need to consider the sample that will be analyzed and the scope of your experiment. For the DSC, the default initial temperature is 50°C and the default final temperature is 200°C.
Heat/Cooling (Ramp) Rate: The acceptable range of ramp rates for conventional DSC is 0.01 to 100°C/minute. This range depends on a number of variables, including the temperature range covered and the presence of a cooling accessory. Faster ramp rates generally increase sensitivity particularly for thermal events such as the glass transition. They also obviously shorten the time of analysis. Slower ramp rates generally provide better resolution (separation of closely spaced thermal events). The heating and cooling in cyclic experiments are usually the same (3 to 5°C/minute).
Number of Cycles: The number of cycles required to assess stability or reversible transitions, such as melting and recrystallization, varies based on material. Several cycles (3 to 5) usually provide a good indication of stability or ensure that no changes occur in the events observed.
Additional Conditions: There are additional experimental conditions that can be changed to optimize specific situations. These are accessed using Advanced Parameters and Post-Test Conditions. For most experiments, the system default values shown are recommended.
:Enter the desired parameters, then select Next to proceed.
Procedure Page:Display the Procedure Page. Select the desired experiment from the list of available preprogrammed templates.
Enter the desired parameters. When you have finished setting up this procedure, you can enter more information by selecting the Notes Page and Summary Page for this run.
Click the Apply button when finished to save these changes or the Append button to save the changes to this run and add another run to the end of the sequence.
NOTE: You can use any test template as the basis for a custom test by selecting the desired test template from the list of tests, then click the Apply button and change the test to Custom. Then you can click on the Procedure Page and then the Editor button to make the changes desired.
