Differential scanning calorimetry (DSC) is a thermal analysis technique that measures the heat flow into or out of a sample as it is heated, cooled, or held at constant temperature. DSC can be used to analyze physical and chemical changes that involve endothermic or exothermic processes, such as phase transitions, crystallization, melting, and curing. DSC provides quantitative and qualitative material characterization by measuring the heat flow and temperature differences between a sample and an inert reference sample as they undergo temperature changes. The heat flow is directly related to transitions in materials and can be used to determine transition temperatures and associated enthalpies.

1. Differential Scanning Calorimetry
(DSC)

2. Thermal Analysis
• Thermal analysis includes a group of
techniques in which specific physical
properties of a material are measured as a
function of temperature.
• Thermal Analysis is useful in both
quantitative and qualitative analysis.
• In Qualitative analysis samples are identified
and characterized by thermal behavior.
• In Quantitative analysis results are recorded
with changes of thermal reaction in weight
and enthalpy

3. Summary Thermal Analysis
Techniques
Technique Quantity Measured Application
Differential
scanning
Calorimetry (DSC)
Heat and temperatures
of transitions and
reactions
Study kinetic
reactions Purity
analysis Polymer
study Polymer
curves study
Differential
thermal Analysis (
DTA)
temperatures of
transitions and
reactions
Phase diagram
Thermal
stability
Thermo gravimetric
analysis (TGA)
Weight changes Thermal stability
Compositional analysis
Thermomechanic
al Analysis (TMA)
Dimensions and
viscosity changes
Study of
temperatures
Expansion
coefficients
Dynamic mechanical
analysis (DMA)
Modules , damping and
viscoelastic behavior
Impact resistance
Mechanical stability
Evolved gas analysis( Amount of gaseous Analysis of volatile

5. History
• The technique was developed by E. S. Watson
and M. J. O'Neill in 1962, and introduced
commercially at the 1963 Pittsburgh Conference
on Analytical Chemistry and Applied
Spectroscopy.
• The first adiabatic differential scanning calorimeter
that could be used in biochemistry was developed
by P.
L. Privalov and D. R. Monaselidze in 1964 at
Institute of
Physics in Tbilisi, Georgia.
• The term DSC was coined to describe this
instrument, which measures energy directly and
allows precise measurements of heat capacity.

6. Principle
• The basic principle underlying this technique is that
when the sample undergoes a physical
transformation such as phase transitions, more or
less heat will need to flow to it than the reference to
maintain both at the same temperature.
• Whether less or more heat must flow to the sample
depends on whether the process
is exothermic or endothermic. For example, as a solid
sample melts to a liquid, it will require more heat
flowing to the sample to increase its temperature at the
same rate as the reference.
• This is due to the absorption of heat by the sample as
it undergoes the endothermic phase
transition from solid to liquid.

7. • Likewise, as the sample undergoes exothermic
processes (such as crystallization) less heat is
required to raise the sample temperature.
• By observing the difference in heat flow between
the sample and reference, differential
scanning calorimeters are able to measure the
amount
of heat absorbed or released during such
transitions.
• DSC may also be used to observe more suitable
physical changes, such as glass transitions. It is
widely used in industrial settings as a quality
control instrument due to its applicability in
evaluating sample purity and for studying polymer.

8. • DSC, change in enthalpy ∆H of the
sample is equal to the difference between
the heat flow of sample and reference
• ∆H= Q s- Q r
• According to thermal analogs of Ohm’s
law,
• Q = T2-T1
Rth
Where Q s and Q r is heat flow from sample
and reference
Rth is thermal resistance

10. Instrumentation
• A typical DSC cell uses a constantan (Cu-
Ni) disk as the primary means of transferring
heat to the sample and reference positions
and also as one element of temperature
sensing thermoelectric junctions.
• The sample and reference are placed in
separate pans that sit on raised platforms on
the disk.
• Heat is transferred to the sample and
reference through constantan disk

11. • The differential heat flow to the the samples and
reference is monitored by the chromel or
constantan thermocouples. Which are formed by
the junction of the constantan disk and the
chromel wafer covering the underside of each
platforms.
• Chromel and aluminium wires are connected to
the underside of the wafers from thermocouple,
which directly monitor the sample temperature.
• Constant calorimetric sensitivity is maintained
by computer software, which linearizes cell
calibration coefficients
• DSC provides maximum calorimetric accuracy
from - 170 to 750 ◦ C
• Sample size ranges from 0.1 to 100 mg
• It measure enthalpy.

15. DSC curves
• The result of a DSC experiment is a curve of heat flux
versus temperature or versus time.
• There are two different conventions: exothermic reactions in
the sample shown with a positive or negative peak,
depending on the kind of technology used in the
experiment.
• This curve can be used to calculate enthalpies of
transitions. This is done by integrating the peak
corresponding to a given transition.
• It can be shown that the enthalpy of transition can be
expressed using the following equation:
∆H =KA
• where ∆H is the enthalpy of transition,
• K is the calorimetric constant, and A is the area under
the curve.

17. Instrumentation Basics:
• Types of DSC Instruments:
1. Power compensated DSC
2. Heat flux DSC
3. Modulated DSC
4. High sensitivity DSC (HS-DSC)
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18. 1.Power compensated DSC:
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19. • In power compensated DSC, the base of the sample holder unit is in direct
contact with a reservoir of coolant.
• Resistance sensor measures the temperature of the base of the holder and a
resistance heater.
• Phase changes in sample temperature difference is detected
electrical power gets supplied to bring temperature difference below
threshold value.
• Temperatures of both are increased or decreased linearly.
• The power needed to maintain the sample temperature equal to the
reference temperature is measured.
 Advantages over Heat flux DSC:
 Its response time is more rapid than heat flux DSC.
 It is also capable of higher resolution.
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20. 2.Heat flux DSC:
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21. • In heat flux DSC, the difference in the heat flow into the sample and
reference is measured while the sample temperature is changed at a
constant rate.
• Both sample and reference are heated by a single heating unit.
• Heat flows into both the sample and reference material via an
electrically heated constant thermoelectric disk is given by
where,
f (T, t) is the kinetic response of the sample in J mol ˉ
ˡ
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22. 3.Modulated DSC Instruments (MDSC) :
• In MDSC, a sinusoidal function is superimposed on the overall temperature
program.
• And produces a micro heating and cooling cycle as the overall temperature
is increased or decreased.
• The overall signal is mathematically deconvoluted into two parts
1. A reversing heat flow signal- Associated with the heat capacity component
of the thermogram .
2. Non- reversing heat flow signal- Associated with the kinetic processes.
 Step transitions appear only in the reversing heat flow signal.
 Exothermic and endothermic events may appear in either or in both
signals.
• It can be useful in resolving polymer glass transitions, which are difficult to
analyze owing to concomitant solvent evaporation.
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23. Sample Preparation
• If possible, clean and dry your sample prior to DSC analysis.
• Wear gloves or use forceps when handling your DSC sample.
• DSC samples should be small enough.
• Powder samples or flat solid samples (less than 2 mm tall) work best.
• Sample weight should be between 0.5 and 100 mg.
DSC sample preparation procedures :
• Weigh sample about 0.5 mg with the analytical balance. Record the weight.
• Use forceps to place sample.
• Use forceps to place the aluminium pan lid on top of your sample.
• Use forceps to load the aluminium pan and sample into the sample encapsulating
press .
• Align the sample pan in the encapsulating press, and press down on the handle to
seal the aluminium pan.
• Use the empty pan as a reference sample.
• Need inert gas like nitrogen to avoid oxidation or decomposition.
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24. Precaution :
Sample Decomposition
 The DSC is capable of heating samples to 600°C.
 Many materials may decompose during the heating, which can
generate hazardous by-products.
WARNING: If you are using samples that may emit harmful gases,
vent the gases in an appropriate manner. In general, samples
should not be heated above their decomposition temperatures to
prevent the release of hazardous materials.
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25. Instrument
Operation
• Powering up the instrument,
• Loading your sample,
• Setting your testing
conditions,
• Running a scan and
collecting
data
• Analyzing your results.
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26. Applications
 Quantitative application includes the determination of heat of fusion and the extent
of crystallization for crystalline materials.
 Glass transition temperatures and melting points are useful for qualitative
classification of materials.
 DSC is used to study ‘aging’ and shelf life of pharmaceuticals, as well as other basic
research and development.
 In the Food Industry, DSC has numerous applications to monitor thermal events
discussed earlier such as melting, crystallization, etc, as well as decomposition,
denaturation , dehydration, polymorphism, oxidation, etc.
 Evaluation of metal catalysts by pressure DSC .
 Measurement of heat capacity
 Measurement of thermal conductivity
1
T2
T
 dT
1
 T 
T2  Cp 
S  T
H  Cp dT
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