Thermal analysis techniques such as differential thermal analysis (DTA) measure the temperature difference between a sample and an inert reference material as they undergo identical thermal cycles. DTA provides information about physical and chemical changes in a material as it is heated, such as melting, crystallization, and decomposition, by detecting endothermic or exothermic reactions. The DTA instrument consists of sample and reference holders connected to thermocouples within a furnace. Changes in the sample are detected as differences in temperature compared to the unreactive reference. DTA is useful for characterizing materials like minerals, polymers, and pharmaceuticals.

1. SUBMITTED BY:
HARSHALA DHENDE
FIRST YEAR M.PHARM
SEM-I
(DEPT. OF PHARMACEUTICS)
Guided By:
Mr. Mukesh T. Mohite
DR. D.Y.PATIL COLLEGE OF PHARMACY, AKURDI, PUNE
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2. Outline…..
 What is Thermal Analysis?
 Types of thermal analysis techniques
 DTA(DIFFERENTIAL THERMAL ANALYSIS)
 Principle involved
 Instrumentation
 Advantages and disadvantages
 Applications
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3. What is Thermal analysis?
Definition of Thermal Analysis (TA):
Thermal Analysis (TA)is a
group of techniques that study the
properties of materials as they change
with temperature.
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4.  When a material is heated its structural and chemical
composition can undergo changes such as fusion,
melting, crystallization, oxidation, transition,
decomposition, expansion and sintering.
 Using Thermal Analysis such changes can be monitored
in every atmosphere of interest. The obtained information
is very useful in both quality control and problem solving.
 In practice thermal analysis gives properties like; enthalpy,
thermal capacity, mass changes and the coefficient of
heat expansion.
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5.  Thermal analysis includes different methods. These
are distinguished from one another by the property which is
measured;
1. ƒThermo gravimetric analysis (TGA): mass
2. ƒ Differential thermal analysis (DTA): temperature
difference
3. ƒDifferential scanning calorimetric (DSC): heat difference
4. ƒPressurized TGA (PTGA): mass changes as function of
pressure.
5. s
6. ƒThermo mechanical analysis (TMA): deformations and
dimension 5

6. 7. ƒDilatometer (DIL): volume ƒ
8. Evolved gas analysis (EGA): gaseous decomposition
products
Often different properties may be measured at the same
time: TGA-DTA, TGA-EGA
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7. 7

8. INTRODUCTION…
 Differential thermal analysis(DTA) is a thermo
analytical technique similar to differential scanning
calorimetric.
 In DTA ,the material under study and an inert
reference are made to undergo identical thermal
cycles ,while recording any temperature difference
between sample and reference.
 This differential temperature is then plotted again
time or, or against temperature.
 The curve plotted is called as DTA curve or thermo
gram. 8

9.  Changes in the sample either endothermic or
exothermic,can be detected relative to the inert
reference.
 Thus a DTA curve provides data on the
transformation that have occurred such as glass
transition, crystallization, melting and sublimation.
 The area under DTA peak is the enthalpy change
and is not affected by the heat capacity of the
sample.
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10. 10
Fig. no 1

11. Fig. no 2 differential thermogram showing types of changes
encountered with polymeric material
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12.  In DTA both the test sample and inert
reference material (alumina) controlled
heating or cooling programming.
 If zero temperature difference b/t
sample and reference material – then
sample doe not undergo any chemical and
physical changes.
If any reaction takes place temperature
difference will occur between sample and
reference material. 12

13. Principle of DTA….
 A technique in which the temperature
difference between a substance and
reference material is measured as function of
temperature, while the substance and
reference are subjected to controlled
temperature programmed.
 The difference in the temp is called as
differential temperature and is plotted against
temp or function of time.
 Physical changes usually result in
endothermic peaks, whereas chemical
reaction those of an oxidative nature show
exothermic peak. 13

14. • Endothermic reaction(absorption of heat)
includes sublimation and gives downward
peak.
• Exothermic reaction(liberation of heat)
includes oxidation, polymerization and
gives upward peak.
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15. Factors causing change in
heat/temperature:
Physical:
 Adsorption(exothermic)
 Desorption(endothermic)
 A change in crystal structure (endo –or exothermic)
 Crystallization (exothermic)
 Melting(endothermic)
 Vaporization (endothermic)
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16. Chemical :-
 Oxidation (exothermic)
 Reduction (endothermic)
 Break down reactions (endo or exothermic)
 Chemisorptions (exothermic)
 Solid state reactions (endo –or exothermic)
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17. INSTRUMENTATION………
 A DTA consists of a ,
1. sample holder
2. thermocouples
3. a furnace;
4. a temperature programmer
5. and a recording system.
 The key feature is the existence of two
thermocouples connected to a voltmeter.
 One thermocouple is placed in an inert material such
as aluminum oxide, while the other is placed in a
sample of the material under study.
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18. 1. Sample holder:
The sample holder and reference cells are made
up of aluminum.
2. Sensors/thermocouples:
Platinum or chromyl thermocouples one for
sample and one for reference material is joined to
differential temperature controller.
3. Furnace:
alumina block containing sample and reference
cells.
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19. 4. Temperature controller:
controls temperature program and
furnace atmosphere
5. Recording system:
It is a system where the change in
the temperature i.e. differential temperature is
recorded and the enthalpy is recorded
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20. 20
Fig. no. 4 Instrumentation

21. Working…
 We need to take two aluminum containers for
keeping the sample as well as reference in them.
• Thermocouples are connected to each of the material
for measuring their temperature, and heat is applied
to them under cautiously regulated conditions.
 Now, if it is seen that the sample material has gone
through certain chemical reaction or physical
transformation, its temperature will change
significantly due to the change in its ‘enthalpy' or
heat content.
 However, the temperature of the reference material
will remain unchanged. 21

22. Working principle ….
22

23. Interpretation of DTA
curve…..
23

24. Factors affect results in DTA….
There are so many factors that affects the DTA
curve. They are divided into two;
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Sample
characteristics
Instrumental
factors

25. Instrumental factors:
Furnace
temperature
Furnace size
and shape
Sample holder
materialHeating rate
Thermocouple
location
25

26. Sample characteristics factors..
Heat
capacity
Swelling
and
shrinkage
of sample
Amount
of sample
Packing
density
Effect of
diluents
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27.  Lets see how these factors effect the DTA
curve and the suggestions…..
Factors Effect Suggestions
1. Heating rate Change in the peak
size and position
Use allow heating rate
2. Location of
thermocouple
Irreproducible curve Standardize
thermocouple location
3. Atmosphere around
the sample
Change in the curve Inert gas should be
allowed to flow
4. Amount of sample Change in the peak
size and position
Standardize sample
mass
5. Particle size of
sample
Irreproducible curve Use small uniform
particle
6. Packing density Irreproducible curve Standardize packing
techniques
7.Sample container Change in peak Standardize container

28. Advantages:
1. Instruments can be used at a very high
temperature
2. Instruments are highly sensitive
3. Flexibility in crucible volume/form
4. Characteristic transition or reaction temperature
can be accurately determined
Disadvantages:
1. Reaction or transition estimations is only 20% to
50% DTA
2. Uncertainty in heats of fusion
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29. Applications of differential
thermal analysis……
 Qualitative and Quantitative identification of
Minerals:
Detection of any minerals in sample.
 Polymeric materials:
DTA is useful for characterization of polymeric
materials in the light of identification of thermo-
physical, thermo-chemical ,thermo-mechanical,
and thermo-elastic changes or transition.
 Measurement of crystalline:
Measurement of the mass fraction of
crystalline material in semi- crystalline polymer.
29

30.  Producing phase diagrams and identifying phase
conversions
 Finding the change in enthalpy (∆H) in the entire procedure
 Fingerprinting certain materials
 Verifying decomposition temperatures of various organic
composites
 Exemplifying inorganic compounds
 Analyzing a physical mixture of commercial polymers
qualitatively
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31.  Quantitative identification and purity assessment of
material are accomplished by comparing the DTA curve of
sample to that of a reference curve
 Impurities may be detected by depression of the M.P.
 DTA is widely used in the pharmaceutical] and food
industries.
 DTA may be used in cement chemistry mineralogical
research and in environmental studies.
 DTA curves may also be used to date bone remains or to
study archaeological materials Using DTA one can obtain
liquids & solidus lines of phase diagrams.
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32. References……..
 Differential thermal analysis (DTA) and differential scanning
calorimetric (DSC) as a method of material investigation,
Greg Klančnik1, *, Josef Medved1 , Primo Mrvar1 1 ,
University of Ljubljana, Faculty of natural science and engineering,
Department of materials and metallurgy, Aškerčeva 12, SI-1000
Ljubljana, Slovenia.
 Introduction to thermal Analysis Techniques and Applications,
Edited by Michael E. Brown Chemistry Department, Rhodes University,
Grahamstown, South Africa KLUWER ACADEMIC PUBLISHERS NEW YORK,
BOSTON, DORDRECHT, LONDON, MOSCOW page no.55-80
 Handbook of differential thermal analysis and colorimetric,
volume 1,
by Patrick K.Gallaghaer, page no.52
32

33. • Principle of instrumental analysis, By Douglas A. Skoog
and F. James Holler,
6th edition page no.62
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