Setting Up a DSC Ramp ProcedureSetting Up a DSC Ramp Procedure
DSC ramp experiments heat or cool the material at a constant rate. The results obtained are affected by the previous thermal history (often imparted on the material during processing [e.g., extrusion]). Therefore, the results are designated "as received.”
If you want to set up a DSC ramp 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 Ramp experiment, baseline calibration experiment, or cell constant/temperature calibration experiment the following parameters need to be chosen:
Start and Final Temperatures: The actual start and final temperatures chosen for a specific experiment must be within the usable temperature of the DSC cell/cooling accessory combination that you are using. 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.
You can choose to start your experiment from one of the following choices:
Current Temperature—the temperature of the DSC cell at the current moment (usually ambient temperature, 30 to 35°C). In this case, the ramped heating begins immediately on starting the experiment.
Another Temperature—you choose the specific temperature desired (default is 50°C). In this case, the system equilibrates at the chosen temperature before ramped heating begins.
Ramp (Heating) Rate: The acceptable range of heating/cooling 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 heating/cooling rates generally increase sensitivity, particularly for thermal events such as the glass transition. They also obviously shorten the time of analysis. Slower heating/cooling rates generally provide better resolution (separation of closely spaced thermal events). Heating rates of 10 to 20°C/minute and cooling rates of 5 to 10°C/minute are a good starting point for most materials.
The temperature range of analysis for the DSC cell is -180 to 725°C, but may be reduced depending on the type of sample pan and cooling accessory used. (NOTE: Only inert gases such as nitrogen can be used above 600°C.) To evaluate materials below room temperature or to run cooling rate experiments, the DSC cell requires a source of external cooling. Typically, this is provided by a liquid nitrogen cooling system, LNCS, (usable from -150 to 550°C) or a refrigerated cooling accessory, RCS, (usable from -90 to 550°C). In addition there are multiple types of DSC pans available. All of them are acceptable for use to 725°C except for aluminum pans, which should only be used to 600°C (aluminum melts at 660°C).
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.
