You can either select one of the preprogrammed test templates or select "Custom" to create your own procedure using the Method Editor. The list of test templates is based on frequently used experimental methods.
Click here to select a test template category:
You have chosen to perform a conventional DSC experiment. Now you need to select which type of experiment to perform from those listed.
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.”
DSC Heat/Cool/Heat experiments are designed to erase previous thermal history by heating the material above a transition (e.g., glass transition or melting), where relaxation or molecular rearrangement can occur, then cooling at a known rate before heating again. The first heating curve provides the “as received” information. The cooling imparts a known thermal history. Therefore, any differences observed between similar materials in the second heating curve are related to real internal differences in the materials (e.g., molecular weight) rather than previous thermal history effects.
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.
DSC Isothermal experiments provide an indication of a material's stability at elevated temperature. The purge gas, which surrounds the material, remains constant or is switched at the elevated temperature to generate a sample-atmosphere interaction (e.g., oxidative stability).
Zero Baseline experiments can be used to adjust the absolute value of the heat flow baseline to zero mW at the lower and upper temperature limits without requiring the complete Tzero calibration procedure. This template should be used between routine Tzero calibration whenever the offset and slope have drifted from zero. It is not necessary to use this template if the full Tzero calibration is performed.
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In MDSC a complex heating profile (temperature regime) is applied to the sample. Specifically, a sinusoidal modulation (oscillation) is overlaid on the conventional linear heating or cooling ramp to yield a profile in which the average sample temperature continuously changes with time but not in a linear fashion. The net effect of imposing this more complex heating profile on the sample is the same as if two experiments were run simultaneously on the material—one experiment at the traditional linear (average) heating rate and one at a sinusoidal (instantaneous) heating rate. The general equation that describes the resultant heat flow at any point in a DSC or MDSC experiment is:
dQ/dt = Cpb + f(T,t)
dQ/dt = total heat flow
Cp = heat capacity
b = heating rate
f(T,t) = heat flow from kinetic (absolute temperature and time-dependent) processes
As can be seen from the equation, the total heat flow (dQ/dt), which is the only heat flow measured by conventional DSC, is composed of two components. One component is a function of the sample's heat capacity and rate of temperature change, and the other is a function of absolute temperature and time. These components are generally referred to as the "reversing" and "nonreversing" heat flows respectively.
The actual complex temperature/time profile in MDSC depends on three variables—underlying heating/cooling rate, modulation period, and modulation temperature amplitude. You will need to select the type of MDSC experiment to perform as seen in the list below.
Conventional MDSC: In conventional MDSC experiments, all three variables are operator-selected for best results and the material is evaluated during heating over a temperature range.
MDSC Heat Only: Only two variables are operator-selectable in heat only MDSC experiments. Those are modulation period and heating rate. The instrument automatically determines the modulation temperature amplitude to ensure that the instantaneous heating rate never goes below zero.
MDSC Quasi-Isothermal: In quasi-isothermal MDSC experiments the underlying heating rate is zero. However, by selecting a modulation temperature amplitude and period, the material is still exposed to an instantaneous heating rate. This provides the ability to obtain heat capacity information while the material is isothermal.
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Calibration of the DSC instrument can be accomplished either by using the Calibration Wizard or manually using the available templates listed below.
Baseline (T1 Heat Flow): The baseline slope and offset calibration involves heating an empty cell through the entire temperature range expected in subsequent experiments. The calibration program is used to calculate the slope and offset values needed to flatten the baseline and zero the heat flow signal. This calibration is used in the Q10 and when the selected heat flow is T1 for the DSC Q100 or Q1000.
Tzero Heat Only Cal and Tzero Heat/Cool Cal: The DSC Tzero* calibration involves two experiments. The first experiment is done without samples or pans (baseline); the second is performed with large (approximately 95 mg) sapphire disks (without pans) on both the sample and reference positions. Both experiments use the same method. The range of temperatures should be at least as broad as the desired experimental range. Tzero calibration should be done at relatively high heating rates such as 20°C/min in order to obtain the most accurate calibration of the sensor thermal capacitance and resistance values. The calibration program is used to analyze the data. Tzero calibration is only used with the DSC Q100 and Q1000 for Heat Flow T4 and T4P. "Heat only calibration" is used when you are interested measuring transitions or heat capacity while heating the sample. The "Heat and Cool calibration" is used when you are interested in both heating and cooling data when measuring transitions or heat capacity (this option takes longer to calibrate).
Cell Constant: This calibration is based on a run in which a standard metal (e.g., indium) is heated through its melting transition. The calculated heat of fusion is compared to the theoretical value using the calibration program. The cell constant is the ratio between these two values. The onset slope, or thermal resistance, is a measure of the suppression of temperature rise that occurs in a melting sample in relation to the thermocouple.
Temperature: Temperature calibration is based on a run in which a temperature standard (e.g., indium) is heated through its melting transition using the same conditions to be used in subsequent experiments (e.g., heating rate and purge gas). The recorded melting point of this standard is compared to the known melting point and the difference is calculated for temperature calibration. The calibration program is used for this analysis. Up to five standards may be used for temperature calibration.
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