Setting Up a DSC Oxygen Induction Time Procedure

Follow the instructions below to perform this operation:

1. Place your samples in the cell and cover the cell.

2. Verify that the correct cooler is specified on the Tools/Instrument Preferences/Cooler page.

3. Display the Procedure Page. Select the "Oxygen Induction Time" test from the list of available preprogrammed DSC templates.

4. Enter the desired test parameters as follows:

• Start Temperature:  The actual starting and upper 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:

1. 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.

2. 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.

• Isothermal (Start) Temperature:  The acceptable range for the equilibration temperature in an isothermal experiment is -180 to 725°C. (NOTE:  Above 600°C can only be used with an inert gas, such as nitrogen.) However, most isothermal experiments are run above ambient.  Standard test methods exist where the equilibration temperature is specified.  For example, polyolefin oxidative stability analysis studies are specified at 200°C based on ASTM Method D3895-80.

• Soak Time:  The soak time is the amount of time you want the sample to hold at the equilibration temperature.

• Switch to Gas 2 (Requires MFC):  The option of switching gas after achieving the equilibration temperature provides the ability to measure material characteristics that are based on not only temperature, but also on the atmosphere around the material (e.g., stability in oxygen [resistance to oxidative degradation]).

• Isothermal Time:  The isothermal time should be set to a value that is greater than required to measure the event of interest.  If the time required is unknown, a large value should be entered.  

• End Experiment When:  No analysis time will be wasted provided a proper "End Experiment" condition is set. DSC isothermal experiments are usually stopped based on detecting heat flows (mW/minute) greater than a "threshold" value.  This threshold should be large enough to ensure that a real event is occurring and that the extrapolated onset can be determined.  0.5 mW/minute is a good initial choice. Check the End Experiment When box and select the desired setting to use this option.

• 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.

5. 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.

6. 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.

Back to top