3. Outlines
• Introduction
• DSC main parts
- Pans - Purge gas - DSC cooling system
• Sample preparation
• DSC working principle
• ICTA & anti ICTA
• DSC curve
• DSC types
3
4. DSC
Differential: measurement of the difference in temperature
or heat flow from sample and reference side
Scanning: the common operation mode is to run
temperature or time scans
Calorimeter: instrument to measure heat or heat flow.
Heat flow: a transmitted power measured in mW
4
5. • The reference pan is to remain empty at all times.
• Signals from both pans provide information to the computer. This allows it to regulate the
temperature and provide a constant heating rate.
• time is heating rate dependent
Metal
1
Metal
2
Metal
1
Metal
2
Sample Empty
Sample
Temperature
Reference
Temperature
Temperature
Difference
• Different heating rate from 1 – 500̊C/min
5 Danley, R. (2003)
6. melting
In, 6.0000 mg
mW
0
-10
-20
120 130 140 150 160 170 °C
^exo
STARe SW 9.10
MSG Lab: NJ
Heat flow
Temperature or
Time
6
7. • made from gold, copper, aluminium, graphite and
platinum, etc.
• The lids can either provide a complete enclosure or
can contain a pin hole to release the pressure that
builds up inside.
• Most samples can be run in non-hermetically sealed
pans either uncovered.
Al Pt alumina Ni Cu quartz
Pan
• Atmospheric interaction is optimised by using an open
(uncovered) pan.
• Sometimes pans coated with an inert fluorophosphates
Layer. This coating renders the pans inert to many
chemicals.
* Care should be taken not to overfill the pan to the point that the sample spills when the pan is being sealed 7
8. purge gas
• chemically inert gas such as Argon or nitrogen
• continuously circulating throughout the cell and purge
the base of the cell and remove any dust, moisture or
other gases that may accumulated as a result of the
pans being heated.
• Nitrogen is most commonly used as a purge gas as it is
• inexpensive, inert and easily available.
• This purge gas gets heated before entering the cell in
order to equilibrate its temperature with that in the
cell.
8
9. DSC cooling system
Simple, Inexpensive and Easy to- Operate but have limited cooling capabilities
- Intercoolers (green coolant similar to Freon)
- like the freezer in a home
- don’t require a lot of maintenance and provide excellent control,
but have defined temperature limits.
Lowest possible temperatures and fastest cooling rates
Dallas, G. (2006)
• Air
• Chillers
• Refrigerated Coolers
• LN2 systems
9
15. Sample Preparation
• Accurately-weigh samples (~3-20 mg)
• Small sample pans (0.1 mL) of inert or treated metals (Al, Pt, Ni,
etc.)
• Several pan configurations, e.g., open, pinhole, or hermetically-sealed
(airtight) pans
• The same material and configuration should be used for the sample
and the reference
• Material should completely cover the bottom of the pan to ensure
good thermal contact
15
Della Gatta, G. et al., (2006)
16. Sample Preparation : Shape
• Keep sample as thin as possible (to minimise thermal
gradients)
• Cover as much of the pan bottom as possible
• Samples should be cut rather than crushed to obtain a
thin sample (better and more uniform thermal contact
with pan)
• Keep sample as thin as possible (to minimize thermal gradient)
• Cover as much of the pan bottom as possible
99
* Small sample masses and low heating rates increase resolution
16
18. DSC working principle
Ice
Air
Ts Tr
Hot Plate
Heat the hot plate from -20 °C to 30 °C,
18
19. Time
or Tr
Temperature
Tr
Ts
Tf
Time
ΔT =Ts-Tr
0
-0.5
Tf
DSC raw signal
19
20. DSC raw signal
Time
or Tr
ΔT =Ts-Tr
0
-0.5
Tf
Time
or Tr
Heat flow (mW)
0
-10
=ΔT/Rth
Rth, thermal
resistence of
the system
DSC signal,
Peak integral -> ΔH
ΔH
20
A normal DSC curve is not horizontal, its baseline shows a slope
21. Endothermic:
Endothermic and exothermic effects
When the sample absorbs energy, the enthalpy change is said to be endothermic.
Processes such as melting, vaporization and gelatinization are endothermic.
Exothermic:
When the sample releases energy, the process is said to be exothermic. Processes
such as crystallization and Gelation are exothermic.
21
22. ICTAC (International Confederation for Thermal Analysis and Calorimetry)
Direction of DSC signal
melting
In, 6.0000 mg
mW
0
-10
-20
120 130 140 150 160 170 °C
^exo
STARe SW 9.10
MSG Lab: NJ
melting
In, 6.0000 mg
mW
20
15
10
5
0
120 130 140 150 160 170 °C
^en do
STARe SW 9 .1 0
MSG L ab: NJ
ICTA (ΔT=Ts-Tr)
endothermic downwards
exothermic upwards.
Anti-ICTA (ΔT=Tr-Ts)
endothermic upwards,
exothermic downwards.
ICTA and Anti-ICTA
ˆexo ˆendo
22
23. DSC Curve
• The result of a DSC experiment is a curve of heat flux
versus temperature or versus time.
• This curve can be used to calculate enthalpies of transitions,
which is done by integrating the peak corresponding to a
given transition.
• Area under the peak is directly proportional to heat
absorbed or evolved by the reaction
23
melting
In, 6.0000 mg
mW
20
15
10
5
0
120 130 140 150 160 170 °C
^en do
24. Factors affecting DSC curve
• Two types of factors effect the DSC curve
1-Instrumental factors
• Furnace heating rate
• Furnace atmosphere
• Geometry of pan holder/location of sensors
• Sensitivity of the recording system
24
25. 2- Sample characteristics
• Amount of sample
• Nature of sample
• Solubility of evolved gases in the sample
• Particle size
• Thermal conductivity
25
26. Influence of Sample Mass
6
150 152 154 156
15mg
Temperature (°C)
0
-2
-4
-6
DSC Heat Flow (W/g)
10mg
4.0mg
1.7mg
1.0mg
0.6mg
Indium at
10°C/minute
Normalized Data
Onset not
influenced
by mass
158 160 162 164 166
26
30. Heat Flux DSC
Furnace
• One block for both sample and reference cells
• sample and reference are heated from the same source and the temperature difference ΔT
is measured
30 Danley, R. (2003)
31. Power Compensated DSC
• sample and reference are heated by separate, individual heaters
• temperature difference is kept close to zero, while the difference in the
electrical power needed to maintain equal temperatures (ΔP = ΔQ/dt) is
measured.
31
32. Power Compensated Perkin Elmer DSC 1
Differential Scanning Calorimter
• Furnace 20 to 600°C
• Maximum scan rate 500°C/min
• Temperature Accuracy: ± 0.1°C
• Sensitivity 0.1μW
• Atmosphere nitrogen or air
• Pyris software
32
34. Modulated DSC
• same heat flux DSC cell is used, but a sinusoidal temperature oscillation (modulation) is
overlaid on the conventional linear temperature ramp
• Two other factors:
the amplitude of modulation
and the period (frequency) of modulation
• Separation of complex transition into more easily interpreted
components
• Increased sensitivity for detection of weak transitions
• Increased resolution of transitions without loss of sensitivity
• Increased accuracy in the measurement of polymer
crystallinity
34
35. Dynamic heating
Types of DSC experiments
Constant heat rate mode
(e.g. heat flow vs. temperature)
Isothermal Mode
Done at constant temperature over a time period
(e.g. heat flow vs. time)
35
42. Parameters to control
• Initial and final temperature
• Heating or cooling rate
• Amount of sample
• Thermal history of sample
• Type of gass: O2, N2, air
• Gas flow rate
* The general rule of thumb is that you should start your run at 20 ˚C below that expected temperature
42
43. DSC Applications
· Glass transition
· Melting points
· Crystallization times and
temperatures
· Heats of melting and crystallization
· Percent crystallinity
· Oxidative stabilities
· Compositional analysis
· Heat capacity
· Purities
· Thermal stabilities
· Polymorphism
43
44. 44
References
Danley, R. New heat flux DSC measurement technique. Thermochimica Acta, 295, 201-208 (2003).
Danley, R.L and Caulfield, P.A. DSC Baseline Improvements Obtained by a New Heat Flow Measurement
Technique. TA Instruments, New Castle, DE 19720 (2001).
Della Gatta, Giuseppe, Michael J. Richardson, Stefan M. Sarge, and Svein Stølen. "Standards, calibration, and
guidelines in microcalorimetry. Part 2. Calibration standards for differential scanning calorimetry*(IUPAC Technical
Report)." Pure and applied chemistry 78, no. 7 (2006): 1455-1476.
Guide for choosing DSC pans. TA Instruments. Thermal applications note. TN-12.
Menczel, J.D. Temperature calibration of heat flux DSC’s on cooling. J. Thermal Anal., 49, 193-199 (1997).
M. J. Richardson, E. L. Charsley. “Calibration and standardisation in DSC”, in Handbook of
Thermal Analysis and Calorimetry, P. K. Gallagher (Series Ed.), Vol. 1, “Principles and
Practice”, M. E. Brown (Ed.), pp. 547–575(1998).
Thermal Advantage Manual. DSC User Reference Guide . (TA Instruments, New Castle, DE.) (2000).
Gide for running software. TA instrument. Theraml application note. TN-12.
Dallas, G. Ph.D. and S. Aubuchon Ph.D. TA Instruments, 109 Lukens Drive, New Castle, DE 19720, USA (2006).
