Thermal analysis

1. Thermal
Analysis
Presented by MENNA KORIAM

2.  Definition
 Methods of analysis:
Thermo Gravimetric Analysis (TGA)
Differential Thermal Analysis (DTA)
Differential Scanning Calorimetric (DSC)
Thermo Mechanical Analysis (TMA)
Dynamic Mechanical Analysis
Dilatometery
Laser Flash Analysis
Thermo-stimulated current
Thermo-luminensce
Evolved Gas Analysis
Recently: Micro calorimetry & Nano calorimetry

3. Definition
Thermal Analysis is a branch of materials science by
which the physical, chemical , and mechanical
properties of materials are studied as a function of
temperature.
This measurement provides information about physical
phenomena, such as phase
transitions, absorption, adsorption and desorption; as
well as chemical phenomena including thermal
decomposition, and solid-gas reactions

4. Methods of Thermal
Analysis
According to the
property measured

5. Thermo Gravimetric
Analysis (TGA)
Differential
Thermal Analysis
(DTA)
Differential
Scanning
Calorimetric (DSC)
Thermo Mechanical
Analysis (TMA)
Dynamic Mechanical
Analysis
Dilatometery
Laser Flash Analysis

6. Thermo-
Gravimetric
Analysis (TGA)

7.  Upon heating a certain material, its weight increases or decreases due to certain
reactions like decomposition, oxidation and dehydration.
 It measures the change in mass or weight in function with the temperature or time with
constant heating rate or constant time.
 TGA is based on that the sample is continuously weighted as temperature is elevated
using an instrument called “thermo balance”.
 Data is recorded in the form of curve called “thermo gram”.
 Instruments which can quantify loss of water, loss of solvent, loss of plasticizer are used
and comparing weight loss of material is being followed

8. 1) Dynamic (scanning mode) TGA:
 this type of analysis the sample is subjected to conditions of continuous
increase in temperature usually linear with time.
2) Static (Isothermal ) TGA:
 this type of analysis the sample is maintained at a constant temperature for a
period of time during which any change in weight is noted.

9.  Components of thermo balance:
1. The balance (electronic micro balance)
2. The furnace (heart)
3. The programmer (brain)
4. The recorder (data collector)

12. 1. Decomposition temperatures
2. Quantitative weight losses
3. Compositional analysis
4. Long term stabilities
5. Flammability properties
6. Rates of degradation
7. Life time of a product
8. Effect of reactive or corrosive atmospheres
9. Oxidative stability of materials

13.  Instrumental factors:
1. Furnace heating rate
2. Furnace atmosphere
 Sample characteristics:
1. Weight of sample
2. Sample particle size

14. I. Materials characterization through analysis of characteristic decomposition
patterns.
II. Can be used to evaluate the thermal stability of a material in a desired
temperature range.
III. Can determine the inorganic or organic content in the sample.

16.  Is a thermo-analytic technique in which the material under study and an inert
reference non reactive material (alumina) are made to undergo identical thermal
cycles.
 Thermocouples measuring temperature of sample and reference material is exposed
to the same heating and cooling schedule via symmetric arrangement in the same
furnace.
 The difference in the temperature profiles of sample and reference material are
recorded as the cycle proceeds.

17.  1) Sample holder comprising thermocouple (is a sensor used to measure
temperature), sample containers and a ceramic or metallic block.
 2) Furnace (must have a uniform hot zone and linear heating).
 3) Temperature programmer (it’s capable of giving a wide range of heating /cooling
rates: usually 1 °c/min to 50 °c/min).
 4) Recording system.

18.  Identical pair of cavities for the sample and reference
material.
 Whole unit is set in an oven – control pressure.
 Thermocouple is placed directly in contact with the sample
and another in contact with the reference.
 When Temperature of the block is raised, the temperature
of the sample and reference also raised.

19.  This differential temperature is then plotted against temperature.
 If temperature difference between sample and reference material is
zero: This means that sample didn’t undergo any chemical or
physical change.
 If there is temperature difference between sample & reference
material: This means that there was a chemical or physical change
in the sample.

22.  Determination of phase diagrams.
 Qualitative and Quantitative identification of minerals: detection of any minerals in a
sample
 Characterization of polymeric materials in the light of identification of thermal,
physical, thermo- chemical, thermo-mechanical and thermo-elastic changes or
transitions.
 Measurement of the mass fraction of crystalline material as in semi- crystalline
polymers.
 Polymers composition.
 Melting point and glass transition temperature (Tg).
 Polymer degradation at the melting point (Tm).
 Polymer molecular weight (low grade – low melting point).
Measurement of the mass fraction of crystalline material as in semi crystalline polymers.

23.  PROS:
 DTA instruments can be used at very high temperatures.
 DTA Instruments are highly sensitive.
 Characteristic transition or reaction temperatures can be accurately determined.
 CONS:
 Uncertainty of heat of fusion, transition, or reaction estimations is 20-50%.

25.  The calorimeter measures the difference in heat flow between the
sample and a blank reference during a non-isothermal
phenomenon, such as polymerization and the melting of metals.
 During a thermal event in the sample, the system will transfer heat
to or from the sample pan to maintain the same temperature in
reference and sample pans.
 Determines series of temperature transitions in materials, such as
the Tg and melting temperature (Tm).

26. The endotherm sudden increase in the number of molecular degrees of
freedom at those transitions, which require energy gain from the environment.
Dynamic exothermic reactions: e.g. during polymerization, the heat
released can be correlated to the amount of reacted vinyl double bonds and the
degree of conversion in real time → But not accurate evaluation of the chemical
structure as it measures it indirectly.

29. 1) Power compensation DSC (two separate individual heaters).

30. 2) Heat flux DSC (single heat source).

31.  In a power compensating DSC, the
endothermic events peak upward as
the instrument must supply more
power to the sample to both furnaces
at the same temperature.
 In a heat flux DSC, these same events
cause the sample to absorb heat
and be cooler than the furnace,
so they point down.

33. 1) Phase diagrams
2) Endothermic or Exothermic reactions
3) Melting temperature.
4) Glass transition temperature (Tg).
5) Percentage of crystallinity.
6) Additives or impurities.
7) Thermal stability.
8) Specific heat.

35.  It is a technique to measure the deformation or the dimensional changes of
the sample under non oscillating force at several frequencies over different
temperature ranges is monitored against temperature or time.
Applications:
 CTE of polymeric materials
 Tg of materials

36. Have a quartz probe which contains a thermocouple for
Temperature measurement of sample and connected linear
variable differential transformer

40.  A sinusoidal strain (oscillating force) is applied to the material at a given
frequency, while the temperature is ramped up or down over a range and
deformation is recorded.
 −50 and 220° C for polymers,
 25 and 600° C for glasses and ceramics
 50 and 600° C for metals
 Sinusoidal motion is the repeated motion in which the dynamic clamp
repeated the same movement over and over with maximum and minimum
values of forces .

42.  Through DMA, some useful properties of materials can be measured,
such as the viscoelasticity, dynamic elastic modulus (E’)
and the glass transition temperature (Tg) in polymers ,
damping behavior , creep recovery behavior .

45. Glass transition temperature (Tg):
 The temperature at which the maximum in the tan delta peak is observed.
 It defines the point at which the material transitions from an elastic to a
rubbery state.

47.  Dilatometer measures change in volume or length caused by physical or chemical
process.
 It can determine linear coefficient of expansion and contraction of the
material.
 ex Like mercury in glass thermometer with graduated scale.

51.  Its used for measuring the thermal diffusivity which is strongly
temperature-dependent, at different temperatures
 The sample can be placed in a furnace at constant temperature.

54.  When the material sample is heated the evolved gases is detected
by spectrometry and useful information can be obtained.
 TGA/STA-MS
Mass spectrometry identifies the evolved molecules after their
ionization based on the m/z ratio of the main ions and their
fragments.
 TGA/STA-FTIR
Chemical functions of the evolved molecules are identified
according to their specific absorption of IR light wavelengths.

57.  Is An Experimental Technique Which Is Used To Study Energy Levels In Semi-
conductors Or Insulators.
 By Measuring Change In The Electric Current With Changing Of Temperature.
 It Provides Additional Information About Molecular Mobility In The Solid State, And
As A Result Characterise Phase Transitions That Are Related To Thermal Transitions In
The Crystalline (Polymorphic) And Amorphous Phases.

60.  When a radiation is incident on a material, some of its energy may be absorbed and
re-emitted as light of longer wavelength.
 Its a form of luminance that is exhibited by certain crystalline materials when
previously absorbed energy from ionizing radiation (pre excited) and re emit it upon
heating as a light.
 Using a light sensitive detector the data can be recorded.
 It is mainly used in archaeology dating.

63. Micro thermal analysis is a technique which combines the thermal analysis
principles of differential scanning calorimetry (DSC) with high spatial resolution of
scanning probe microscopy.
 real-time monitoring and dynamic analysis of chemical, physical and biological
processes. Over a period of hours or days.
 determines the onset, rate, extent and energetic of such processes for specimens in
small ampoules (e.g. 3–20 ml) at a constant set temperature (c. 15 °C–150 °C).
 Nano thermal analysis which uses micro fabricated self-heating silicon
cantilevers to probe thermo mechanical properties of materials with sub-100 nm
spatial resolution