SCHOOL OF MATERIAL
THERMAL ANALYSIS AND
CALORIMETRY OF MATERIALS
Presented by: PL Teh
• A group of techniques in which a porperty of the
material is monitored against time or temperature
of the material on a specified atmosphere, which
• May involve heating or cooling at a fixed rate of
temperature change, or holding the temperature
constant, or any sequence of these.
Technique Abbreviation Measurement Applications
Thermogravimetry TG Mass Decomposition
(Thermogravimetric TGA Dehydration
Differential Scanning DSC Power (heat Phase transition
Calorimetry flow) Heat capacity
difference Reaction kinetics
Thermomechanical TMA Expansion Expansion,
Analysis volume change
Dynamic Mechanical DMA Moduli
Analysis Mechanical Phase
Loss change, internal
Thermogravimetric Analysis (TGA) measures the amount
and rate of change in the weight of a material as a function
of temperature or time in a controlled atmosphere.
Measurements are used primarily to determine the
composition of materials and to predict their thermal
stability at temperatures up to 1000°C.
The technique can characterize materials that exhibit weight
loss or gain due to decomposition, oxidation, or dehydration.
• As sample changes weight, its tendency to rise or fall is detected by the LVDT.
• A linear variable differential transformer (LVDT) is used as a sensor of the balance
movement to register changes in the sample mass.
• A current through the coil on the conterbalance side exerts a force on the
magnetic core which acts to return the balance pan to a null position.
• This current is directly proportional to the sample mass change.
TGA can give informations:
❑ Thermal Stability of Materials
❑ Oxidative Stability of Materials
❑ Composition of Multi-component Systems
❑ The Effect of Reactive or Corrosive
Atmospheres on Materials
❑ Determine of moisture, volatiles and ash content
Typical TG curves
1. no change
2. desorption/drying (rerun)
3. single stage decomposition
4. multi-stage decomposition
5. as 4, but no intermediates or heating rate
6. atmospheric reaction
7. as 6, but product decomposes at higher
and ash content
Differential Scanning Calorimetry
• DSC is a thermal analysis method where differences in heat
flow into a substance and a reference are measured as a
function of sample temperature, while both are subjected to
a controlled temperature program.
• As chemical reactions (such as curing, burning, etc) and many
physical transitions (such as melting, crystallization, and many
other structural transitions in solids) are connected with the
generation or consumption of heat, calorimetry is a widely
used technique for investigating such process.
• The objective of calorimetry is to measure the amount of heat
and the transition temperature associated with various
chemical and physical transitions.
• Heat capacity/specific heat: ability of a material to
store thermal energy. When an amount of heat Q is
supplied to a material, its temperature will be raised
by ∆T ; Q = mC ∆T
m: sample mass. C is a material property, called heat
capacity or specific heat.
The heat capacity of the system is the quantity of heat needed to raise
the temperature of the system of 1oC. To obtain the heat capacity we
have to know the equation (1).
Heat Capacity: Examples
Examples of heat capacity:
Al : 0.215 cal/g K
Liquid water: 1.00
This is why it is much easier to heat up
copper than trying to boil the same quantity
When a material changes from solid form to liquid (melting),
or liquid to gas (vaporization), a certain amount of energy is
• A chunk of ice kept at 0 o C won’t change into 0o C water if
no additional heat is supplied. This additional amount of
heat is called the latent heat
• Latent heat of melting (heat of fusion):
Ice: 80 cal/g
Lead: 5.9 cal/g
Silver: 21 cal/g
For a multi-component system, the temperature may or may
not change during such phase transitions
Calorimetry: measurement of heat energy associated with
changes of state (such as melting or freezing) and chemical
Differential: Comparison. Difference between the sample and a
standard material which has no chemical reaction or changes of
state during the temperature range of consideration.
Scanning: temperature is usually scanned at a constant heating or
cooling rate (0 to 200°C/min).
Exothermic reaction: sample releases heat during the reaction
(such as crystallization, curing, or freezing).
Endothermic reaction: sample needs extra amount of heat energy
to complete the transition (such as melting).
Hest Flux vs Power Compensation
The Glass Transition Temperature, Tg
• This means heat is being absorbed by the sample. It also means that we
have a change (increase) in its heat capacity.
• This happened because the polymer has just gone through the glass
• Polymer have a higher heat capacity above the glass transition
temperature than they do below it.
Effect of Heating Rate on the Tg
Effect of Molecular Weight on the Tg
Effect of Hydrogen Bonding on the Tg
Effect of Plasticizer on the Tg
Effect of Bulky Substituent on the Tg
Effect of Flexible
Substituents on the
Effect of Intermolecular Interactions
• Above the glass transition, the polymers have
a lot of mobility.
• They wiggle and squirm, and never stay in one
position for very long.
• When they reach the right temperature, they
will have gained enough energy to move into
very ordered arrangement, which called
• When polymers fall into these crystalline arrangements, they give off
• You can see this as a big peak in the plot of heat flow vs temperature.
Exo • The area under the melting
curve is proportional to
T amount of heat required to
c melt the sample such as the
heat of fusion.
• If we know the theoretical
Temperature heat of fusion of pure
polymer, we can calculate the
crystallinity (%) of the sample
from its measurement by
Measurement of Crystallization
• This means that when you reach the melting
temperature, the polymer’s temperature
won’t rise until all the crystals have melted.
• This also means that the furnace is going to
have to put additional heat into the polymer
in order to melt both the crystal and keep the
temperature rising at the same rate as that of
the reference pan.
Measurement of Melting
Effect of Aromaticity on Melting
Effect of Polymer Type on Melting
Effect of Molecular Weight on Melting
Effect of Hydrogen Bonding on Melting
Effect of Heating Rate on Nylon 66
• If you look at the DSC plot you can see a big difference
between the glass transition and the other two thermal
transitions,c rystallization and melting.
• For the Tg, there is no peak, and there is no dip either.
This is because there is no latent heat given off, or
• Both melting and crystallization involve absorbing or
giving off heat. The only thing we do see at the Tg is a
change in the heat capacity of the polymer.
• Because there is a change in heat capacity, but
there is no latent heat involved with the Tg,
we call the Tg second order transition.
• Transition like melting and crystallization
which do have latent heats are called first
DSC plot output
• To put them all together, a whole plot will
often look something like this :-
Examples of Tg
DSC Thermoset Cure: First and
• Curve 1 is the
measurement result of
base compound, Tg at
• Curve 2 is the
measurement result for
the curing agent, Tg at -
• Curve 3 shows the
results when the base
compound and curing
agent were mixed.
• Curve 4 shows the
results for the 2nd
heating, Tg observed at
18.5°C and 105.5°C
• The mixture left to
curing at room
different lengths of
• The longer the
curing time at
the higher the Tg
• The shape and
temperature of the
change the degree
Cure kinetics of resins
❖ Cure kinetics of resins systems are studied using non-isothermal
and isothermal methods.
❖ Ozawa and Kissinger are the two kinetic analysis models that
extensively used to understand and predict the cure behaviour
of the resin systems.
❖ Basic assumption: the rate of kinetic process (dα/dt) is
proportional to the measured heat flow Φ and Δ the enthalpy
of the reaction.
❖ The rate of the kinetic process in kinetic analysis can be
Where ( ) is heat flow from kinetic
A is the pre exponential factor (frequency
is the activation energy.
R is the gas constant (8.314 J/mol/K) and
T is the absolute temperature
❖ The slope of ln dα/dt versus 1/T gives the value of activation
is the heating rate,
is the activation energy, and
R = 8.314 J/°K-mol is the gas constant.
Tp = The peak of exotherm temperature
Activation energy can be was calculated from the slope of the plot of (ln )against (1/ )
is the heating rate,
is the activation energy and
R = 8.314 J/°K-mol is the gas constant.
The activation energy can be obtained from the slope of the plot of ( / 2) against (1/ )
traces for thermoset at
different heating rate.
The shifting of the DSC
peak as a function of
heating rate can provide
about the curing
To estimate the
was used in which ln (θ/
Tp2) is plotted against
where is the heating rate, Tp is the peak temperature (in K) of the curing
The slope of this plot is -E/R (R = 8.314 J/mol, K is the Universal Gas constant).
Experimentally, we observed
that the onset of cure time
has an Arrhenius temperature
t = A exp(E/RT)
E: activation energy;
R: Universal Gas Constant;
T: absolute temperature;
Based on the slope of the linear fit, the activation energy E is calculated to be 89.1
kJ/mol, this can be used to predict the curing behavior at other temperatures.
For example, at 25 o C, it would take 67 days to reach the onset of cure.
The information allows us to have some idea about the material pot life at various
Dynamic Mechanical Analysis
Dynamic Mechanical Analysis
• A Dynamic Mechanical Analyzer (DMA) is used to measure the
stiffness and damping properties of a material.
• DMA is a technique where a small deformation is applied to a
sample in a cyclic manner. This allows the materials response
to stress, temperature, frequency and other values to be
• The DMA determines changes in sample properties resulting
from changes in five experimental variables: temperature,
time, frequency, force, and strain.
Dynamic mechanical analysis
• In viscous systems: all the work done by the system is
dissipated as heat
• In elastic systems: all the work is stored as potential energy
• Polymer = viscoelastic behavior (dual manner)
• DMA is an excellent technique for extracting information on
the dynamic material properties which relate to these two
regimes of behavior.
• DMA measurements can give the following properties as a
function of temperature:
• the elastic modulus (E'):
represents how much energy the polymer stores
• the viscous modulus (E"):
indicates the polymer's ability to dissipate the
energy as heat.
When the strain is in phase with stress, i.e δ is
0º , the sample is classed as elastic. An
example of an elastic material might be a
rubber band or a metal spring.
When the strain is 90º out of phase with the
stress, i.e δ is 90º, the sample is classed as
viscous. Viscous materials such as Glycerine
exhibit large damping properties.