Setting Up an MDSC®
Heat-Iso ProcedureSetting Up an MDSC®
Heat-Iso Procedure
Three variables are adjusted to obtain the desired MDSC temperature profile—the underlying heating, modulation period, and temperature amplitude of modulation. When studying melting events, it is beneficial to adjust these variables so that the minimum instantaneous heating rate achieved is 0°C/minute (isothermal). By not cooling the material at any time during the modulation, the possibility for "artificially" affecting any observed crystallization phenomena is eliminated. More importantly, when the instantaneous heating rate is zero, there is no heat flow associated with heat capacity and, therefore, any heat flow observed at the top of the raw modulated heat flow signal must be the result of kinetic phenomena.
If you want to set up an MDSC heat-iso experiment, 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 MDSC Heat/Isothermal experiment, the following parameters need to be chosen:
Start Temperature & Final Temperature: The starting and final temperatures should be set to cover a wide enough temperature range to observe all the events of interest. As in conventional DSC, the maximum range is -180 to 725°C but may be reduced depending on the type of sample pan and cooling accessory used.
Heating Rate: Select an underlying heating rate of 5°C/minute or less, if required to get a minimum of four modulation cycles over the width of the melting peak (measure at half-height).
Modulation Period: Use a modulation period of 40 seconds. Longer periods (60 seconds) are recommended for polymer samples greater than 15 mg.
Modulation Temperature Amplitude: Once the values above are entered, the temperature amplitude of modulation will automatically be determined based on the following equation.
Tamp = Hr x P/2p(60)
where:
Hr = underlying heating rate
P = modulation period (min)
NOTE: You do not need to enter a value, this is a read-only field.
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.
Modulated DSC® and MDSC® are registered trademarks of TA Instruments—Waters LLC.
Modulated DSC® and MDSC® are terms which describe proprietary technology invented by Dr. Mike Reading of ICI Paints (Slough UK) and patented by TA Instruments—Waters LLC (U.S. Patent Nos. B1 5,224,775; 5,248,199; 5,335,993; 5,346,306).
