MODULATED DSC

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MODULATED DSC?
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WHAT IS MDSC??

• In MDSC, a sinusoidal heating profile is
  overlaid on the standard linear ramp
• From this experiment, the standard Heat Flow
  curve is separated into two components called the
  Reversing Heat Flow and the Non-Reversing Heat
  Flow
• Total Heat Flow is the same as in standard DSC
• Reversing Heat Flow is the Cp component
• Non-Reversing Heat Flow is the Kinetic Component

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MDSC heating profile
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Experimental conditions
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Raw data
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MDSC? EXAMPLE ON PET
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Tzero? MDSC?

• Results obtained using current MDSC practice are
  strongly dependent on modulation period
• Long periods are required
• Low heating rates necessary
• Tzero MDSC greatly reduces period dependence
• Shorter periods may be used
• Higher heating rates are possible

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FAST MDSC?
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Lactose
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HEAT CAPACITY SIGNAL
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WHAT IS HEAT CAPACITY?

• Heat capacity is the amount of heat required to
  raise or lower the temperature of a material.
• Specific heat capacity refers to a specific mass
  and temperature change for the material (J/gC)

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WHY IS HEAT CAPACITY IMPORTANT?

• Thermodynamic property of material(vs. heat flow)
• Measure of molecular mobility
• Provides useful information about physical
  properties of the material as a function of
  temperature

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BENEFITS OF MEASURING HEAT CAPACITY

• Structure-property information
• Can compare samples run at different heating
  rates
• Can compare samples during heating and cooling to
  better identify transitions associated with heat
  capacity and kinetic processes
• Can be used to measure absolute crystallinity of
  polymers as a function of temperature (Vincent
  Mathot, 1997 NATAS Conference Proceedings)

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MDSC? METHOD

• MDSC heat capacity equation applies to heat flow
  to a single body
• DSC heat flow is the difference between sample
  and reference heat flows
• The method does not properly account for phase
  and amplitude differences between sample and
  reference heat flows and temperatures

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Tzero? MDSC? METHOD

• Tzero DSC gives independent sample and reference
  heat flow
• Deconvolute sample and reference heat flow
  separately
• Subtract reference reversing and non-reversing
  heat flow from sample reversing and non-reversing
  heat flow
• Period dependence is greatly reduced
• Cp units available for all signals

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Tzero? MDSC? HEAT CAPACITY CALIBRATION
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HEAT CAPACITY UNITS ON ALL SIGNALS