Specific Heat Capacity of a
Material
Thermal Analysis : Dr. A. Sedghi
Dr. Arman Sedghi
(IKIU)
Calorimetry
Two types of calorimetry are commonly used:
◦ Constant-pressure Calorimetry
Specific heat
DHrxn or DHsoln
◦ Bomb Calorimetry (Constant Volume Calorimetry)
DHcombustion
Thermal Analysis : Dr. A. Sedghi
Calorimetry
In constant-pressure calorimetry,
◦ Measurements are made in an “open” container.
Reactions occur at constant pressure
◦ Calorimeter is insulated
Assume that the amount of heat gained from or lost to
the surroundings is negligible
any heat gained or lost during a chemical reaction or process
comes from or goes into the solution being studied.
Thermal Analysis : Dr. A. Sedghi
Calorimetry
In constant-pressure calorimetry, the heat
gained or lost by the solution (the liquid
present) is measured.
◦ If heat is lost by the chemicals (or object) during a
reaction or process, then it must be gained by the
solution and vice versa.
The heat lost or gained by the reaction (or object) and
the solution are equal in magnitude but opposite in sign.
qobj = - qsoln or qrxn = - qsoln
Thermal Analysis : Dr. A. Sedghi
Calorimetry
Calorimetry Simulation:
◦ Measuring the specific heat of a metal
How is the experiment performed?
What kind of data is collected?
How are the data used to determine specific heat?
Thermal Analysis : Dr. A. Sedghi
Calorimetry
Determining specific heat or molar heat capacity experimentally:
◦ Heat an object with a known mass to 95-100oC.
◦ Measure initial temperature of object.
◦ Place known mass of water into calorimeter and measure its temperature.
◦ Add hot object to the water
◦ Measure the equilibrium temperature (i.e. final temperature) of the water and object.
Thermal Analysis : Dr. A. Sedghi
Calorimetry
Types of data obtained from or used in a calorimetry experiment often include: ◦ Sample Data Mass of sample (object or compound)
Tinitial (sample)
Tfinal (sample)
◦ Solution Data Mass of solution
Tinitial (solution)
Tfinal (solution)
Csoln Often use specific heat of water if water is the solvent
Thermal Analysis : Dr. A. Sedghi
Calorimetry
Using the data to find specific heat:
◦ Calculate the amount of heat gained by the water:
qwater = Cwater x mwater x DTwater
◦ Calculate the amount of heat lost by the object qobj = - qwater
◦ Calculate specific heat of object
Cobj = qobj
mobj x DTobj
Thermal Analysis : Dr. A. Sedghi
Calorimetry
Example: A 55.0 g piece of aluminum metal at 100.0oC was added to 51.3 g of water at 20.0oC. The equilibrium temperature of the system was 35.0oC. If the specific heat of water is 4.18 J/g.K, what is the specific heat of aluminum?
Thermal Analysis : Dr. A. Sedghi
Given: Cwater = 4.18 J/g.K
mwater = 51.3 g
DTwater = 35.0oC - 20.0oC = 15.0oC = 15.0 K
mAl = 55.0 g
DTAl = 35.0oC - 100.0oC = -65.0oC = -65.0K
Find: CAl
Calorimetry
qwater = Cwater x mwater x DTwater
qwater = 4.18 J x 51.3 g x 15.0 K = 3216.5 J
g.K
q Al = -qwater = -3216.5 J (Note: Keep some extra sig figs at this stage)
CAl = qAl = -3216.5 J
mAl x DTAl 55.0 g x -65.0 K
CAl = 0.900 J/g.K
Thermal Analysis : Dr. A. Sedghi
Calorimetry
For an exothermic process, the heat produced causes the temperature of the solution to increase. (DTsoln >0)
Thermal Analysis : Dr. A. Sedghi
Chemical
particle
Heat released by chemical
particle
q
q
q q
q
q q
Calorimetry
For an endothermic process, the heat gained comes from the reaction mixture and causes the temperature of the solution to decrease (DTsoln < 0)
Thermal Analysis : Dr. A. Sedghi
Chemical
particle
Heat gained by chemical particle
from the rxn mixture
q
q
q
q
q
q
Calorimetry
Bomb Calorimetry
◦ Constant Volume
Calorimetry
◦ Used to study combustion
reactions
◦ Measure DHcombustion
Thermal Analysis : Dr. A. Sedghi
Calorimetry
As combustion occurs,
◦ Heat is released
◦ Heat is absorbed by the calorimeter and its
contents
◦ Temperature of calorimeter & contents increases.
The change in temperature of the calorimeter
and its contents can be used to determine the
heat of combustion.
Thermal Analysis : Dr. A. Sedghi
Calorimetry
Calculate the heat absorbed by the calorimeter and its contents:
qcal = heat capacity (calorimeter) x DT
(Notice that you do not need a mass term because heat capacity has units of J/K)
Calculate the heat lost by the reactants:
qrxn = -qcal
Thermal Analysis : Dr. A. Sedghi
Calorimetry
Calculate molar heat of combustion
(DHcomb per mole reactant)
◦ DHcomb = qrxn
mole reactant
Thermal Analysis : Dr. A. Sedghi
Calorimetry
Example: When 2.00 g of methylhydrazine (CH6N2) is burned in a bomb calorimeter, the temperature of the calorimeter increases from 25.00oC to 32.25oC. If the heat capacity of the calorimeter is 7.794 kJ/oC, what is the molar heat of combustion for CH6N2?
Thermal Analysis : Dr. A. Sedghi
2CH6N2 (l) + 5 O2(g) 2 N2 (g) + 2 CO2(g) + 6 H2O (g)
Calorimetry
Given: Tfinal = 32.25oC
Tinitial = 25.00oC
Ccal = 7.794 kJ/oC
Find: molar heat of combustion
Thermal Analysis : Dr. A. Sedghi
DT = 32.25 - 25.00
= 7.25oC
DHcomb = qcomb
mol CH6N2
Calorimetry
qcal = Ccal x DT
qcal = 7.794 kJ x 7.25 K = 56.51 kJ
K
qrxn = -qcal = -56.51 kJ
DH = - 56.51 kJ x 46.1 g = -1.30 x 103 kJ
2.00 g mole mole
Thermal Analysis : Dr. A. Sedghi
DHcomb = qrxn
mole CH6N2
Hess’s Law
The heats of reaction (DHrxn) have been measured and tabulated for many chemical reactions.
There are two approaches to determining the heat of reaction for a particular chemical reaction:
◦ Calorimetry
◦ Use tabulated DHrxn to calculate the heat of reaction for another reaction of interest
Thermal Analysis : Dr. A. Sedghi
Hess’s Law
The enthalpy change for a reaction or
process is a state function:
◦ Depends only on the amount of reactants and
products used/formed and on their physical
state
◦ Does not depend on how the reaction was
done.
one step vs. multiple steps
Thermal Analysis : Dr. A. Sedghi
Hess’s Law
Hess’s Law:
◦ If a reaction is carried
out in a series of steps,
DH for the overall
(one-step) reaction is
equal to the sum of
the DH for the
individual steps.
Thermal Analysis : Dr. A. Sedghi
Experimental Procedure
There are four main procedures to this experiment
1. Set-up the calorimeter
2. Boil the water containing metal
3. Set-up the GLX computer.
4. Collect the calorimetric data.
Thermal Analysis : Dr. A. Sedghi
Background - Calorimeter
Thermal Analysis : Dr. A. Sedghi
Thermometer
probe insert
Calorimeter
cover or lid
Two styrofoam cups
nested together
containing water and
metal
GLX
Xplorer
Analog
Adapter
GLX
Adapter
USB
Plug
Figure A- GLX Components
Thermal Analysis : Dr. A. Sedghi
Colorimeter
Voltage
Sensor Syringe
Pressure
Sensor
Temperature
Sensor
pH Sensor
Figure B- Sensor Probes
Thermal Analysis : Dr. A. Sedghi
Calorimetric Set-Up
Thermal Analysis : Dr. A. Sedghi
Differential Scanning Calorimetry (DSC)
Thermal Analysis : Dr. A. Sedghi
Analogous to DTA, but the heat input to sample and reference is varied in
order to maintain both at a constant temperature.
Key distinction:
– In DSC, differences in energy are measured
– In DTA, differences in temperature are measured
DSC is far easier to use routinely on a quantitative basis, and has become the
most widely used method for thermal analysis
Differential Scanning Calorimetry (DSC)
Polymer and reference samples are heated in such a way that they are kept
at the same (increasing) temperature.
When a thermal transition occurs thermal energy is supplied to the
polymer or reference.
The energy transferred is equivalent to the energy absorbed or evolved in
the transition.
Thermal Analysis : Dr. A. Sedghi
DSC Instrumentation
Thermal Analysis : Dr. A. Sedghi
There are two common DSC methods
– Power compensated DSC: temperature of sample and reference are kept
equal while both temperatures are increased linearly
– Heat flux DSC: the difference in heat flow into the sample/reference is
measured while the sample temperature is changed at a constant rate
• DSC differs fundamentally from DTA in that the sample and reference are both maintained at the temperature predetermined by the program.
• 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
• two basic types of DSC instruments: power compensation and heat-flux
Differential Scanning Calorimetry
power compensation DSC heat flux DSC
Thermal Analysis : Dr. A. Sedghi
Power Compensation DSC
sample holder • Al or Pt pans
sensors • Pt resistance thermocouples • separate sensors and heaters for the sample and reference furnace
• separate blocks for sample and reference cells
temperature controller
• differential thermal power is supplied to the heaters to maintain the temperature
of the sample and reference at the program value
sample pan
DT = 0
inert gas vacuum
inert gas vacuum
individual heaters
controller DP
reference pan
thermocouple
Thermal Analysis : Dr. A. Sedghi
DSC
Thermal Analysis : Dr. A. Sedghi
sample holder • sample and reference are connected by a low-resistance heat flow path • Al or Pt pans placed on constantan disc
sensors • chromel®-constantan area thermocouples (differential heat flow) • chromel®-alumel thermocouples (sample temperature) furnace
• one block for both sample and reference cells
temperature controller
• the temperature difference between the sample and reference is converted to
differential thermal power, dDq/dt, which is supplied to the heaters to maintain the temperature of the sample and reference at the program value
Heat Flux DSC
sample pan
inert gas vacuum
heating coil
reference pan
thermocouples
chromel wafer
constantan
chromel/alumel wires
Thermal Analysis : Dr. A. Sedghi
Analysis of Heat-Flow in Heat Flux DSC
• temperature difference may be deduced by considering the heat flow paths in the DSC system
• thermal resistances of a heat-flux system change with temperature
• the measured temperature difference is not equal to the difference in temperature between the sample and the reference
DTexp ≠ TS – TR
tem
pera
ture
Tfurnace
TRP
TR
TS
TSP
heating block
DTR DTS
reference
sample
DTL
thermocouple is not in physical contact with sample
Thermal Analysis : Dr. A. Sedghi
Derives H Uses thermocouples
Power Compensation DSC Quantitative DTA “Heat Flux” DSC
Measures H directly Uses platinum resistance
thermometers
Diamond DSC
Pyris 6 DSC
Sapphire DSC
Competitive DSC’s
DSC Technology …
Thermal Analysis : Dr. A. Sedghi
Heat Flux DSC furnace
Power Compensation DSC
furnace
The different DSC technologies …
High resolution / high sensitivity research studies
Absolute specific heat measurement
Fast Scan DSC applications (HyperDSCTM)
High throughput laboratories
Thermal Analysis : Dr. A. Sedghi …. are tailored for specific applications
Routine applications
Near / at line testing in harsh environments
Education
Automated operation
Cost-sensitive laboratories
Power Compensation DSC
Heat Flux DSC
DSC
Constant Heating Rate
◦ Initial Temp
◦ Final Temp
◦ Heating Rate (°C/min)
Data
◦ Heat flow to sample minus
Heat flow to reference vs Time
(Temp.)
Measures heat of
crystallization
Thermal Analysis : Dr. A. Sedghi
Polymer without weight change in this temperature range
Typical Features of a DSC Trace for a Polymorphic System
sulphapyridine
endothermic events
melting sublimation
solid-solid transitions desolvation
chemical reactions
exothermic events
crystallization solid-solid transitions
decomposition chemical reactions
baseline shifts
glass transition Thermal Analysis : Dr. A. Sedghi
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 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
• avoid overfilling the pan to minimize thermal lag from the bulk of the material to the sensor
* small sample masses and low heating rates increase resolution, but at the expense of sensitivity
Al Pt alumina
Ni Cu quartz Thermal Analysis : Dr. A. Sedghi
DSC Calibration
baseline • evaluation of the thermal resistance of the
sample and reference sensors
• measurements over the temperature range of interest
2-step process
• the temperature difference of two empty crucibles is measured
• the thermal response is then acquired
for a standard material, usually sapphire, on both the sample and reference platforms
• amplified DSC signal is automatically varied with temperature to maintain a constant calorimetric sensitivity with temperature
Thermal Analysis : Dr. A. Sedghi
DSC Calibration temperature • goal is to match the melting onset temperatures indicated by the furnace
thermocouple readouts to the known melting points of standards analyzed by DSC
• should be calibrated as close to the desired temperature range as possible Hea
use of calibration standards of known heat capacity, such as sapphire, slow accurate heating rates (0.5–2.0 °C/min), and similar sample and reference pan weights
t flow calibrants • high purity • accurately known enthalpies • thermally stable • light stable (hn) • nonhygroscopic • unreactive (pan, atmosphere)
metals • In 156.6 °C; 28.45 J/g • Sn 231.9 °C • Al 660.4 °C inorganics • KNO3 128.7 °C • KClO4 299.4 °C organics • polystyrene 105 °C • benzoic acid 122.3 °C; 147.3 J/g • anthracene 216 °C; 161.9 J/g
Thermal Analysis : Dr. A. Sedghi
Heat Flow in DSC
Thermal Analysis : Dr. A. Sedghi
DSC Step by Step
Thermal Analysis : Dr. A. Sedghi
Melting Glass transition Recrystallization
Applications of DSC
Thermal Analysis : Dr. A. Sedghi
DSC is usually carried out in
linear increasing-temperature
scan mode (but can do
isothermal experiments)
– In linear scan mode, DSC
provides melting point data
for crystalline organic
compounds and Tg for
polymers
Easily used for detection of bound crystalline water molecules or solvents,
and measures the enthalpy of phase changes and decomposition
DSC trace of polyethyleneterphthalate (PET)
Applications of DSC
Thermal Analysis : Dr. A. Sedghi
DSC is useful in studies o
polymorphism in organic
molecular crystalline
compounds (e.g.
pharmaceuticals, explosives,
food products)
Example data from two
“enantiotropic” polymorphs
DSC of a Pharmaceutical Hydrate
Thermal Analysis : Dr. A. Sedghi
Loss of water
Melt Decomposition
A Differential Scanning Calorimeter (DSC) measures the amount of energy (heat)
absorbed or released by a sample as it is heated, cooled or held at a constant
(isothermal) temperature. The precise measure of sample temperature is also
made with a DSC.
Thermal Analysis : Dr. A. Sedghi
Differential Scanning Calorimetry (DSC) …
High Sensitivity Thermal Analysis DSC family ...
Thermal Analysis : Dr. A. Sedghi
Researc
h
Diamond DSC • Unique Power Compensation
• HyperDSCTM for unmatched
sensitivity
• Highest signal resolution
• StepScan SW for MTDSC
Sapphire DSC • Heat Flux DSC • Oval sensor for high sensitivity • Fully automated • Multiple cooling options and
pan types for broad operation range
Pyris 6 DSC • Heat Flux DSC • Low cost • Rugged and reliable • Fully automated • Built-in mass flow control
Routine
DSC Plot
The resulting plot of differential rate of heating Vs
temperature can be studied to measure Heat capacity, melt
enthalpy and transition temperature.
Thermal Analysis : Dr. A. Sedghi
Completely amorphous polymers won't show any crystallization, or any
melting either. But polymers with both crystalline and amorphous domains,
will show all the features you see above.
Characteristics of a DSC curve
Each substance has a characteristic DSC curve that can
be used for qualitative identification.
Endotherms generally represent physical changes while
exotherms indicate crystallization, polymerization,
curing, decomposition etc.
The area under the peak (trough) is proportional to the
heat evolved or absorbed during the reaction.
Thermal Analysis : Dr. A. Sedghi
Applications of the DSC curve
% Crystallinity
% Crystallinity = D Hf,x/D Hf
= Heat of fusion of sample/heat of fusion of 100% crystal
Rate of reaction
◦ Height of peak is proportional to rate of reaction
Heat of reaction = Heat absorbed or emitted/No of moles
Change in heat capacity
◦ Manifests as a change in baseline.
◦ A sharp increase is typical of Tg. Thermal Analysis : Dr. A. Sedghi
Melting point from DSC curve
Melting point - Can determine the exact melting
point as the temperature at which melting is
complete. The actual melting of the polymer takes
place at a range of temperature.
Thermal Analysis : Dr. A. Sedghi
Definition of Transition Temperature
157.81°C
156.50°C28.87J/g
-2.5
-2.0
-1.5
-1.0
-0.5
0.0
0.5
He
at
Flo
w (
W/g
)
140 145 150 155 160 165 170 175
Temperature (°C)
Sample: INDIUM CRIMPED PAN CHECKSize: 7.6300 mgMethod: indiumComment: P/N 56S-107
DSCFile: C:...\10C per min crimped\DSC010920A.3Operator: Ron VansickleRun Date: 20-Sep-01 09:13Instrument: 2920 MDSC V2.6A
Exo Up Universal V3.3B TA Instruments
extrapolated onset temperature
peak melting temperature
Thermal Analysis : Dr. A. Sedghi
Melting Processes by DSC
pure substances • linear melting curve
• melting point
defined by onset temperature
impure substances • concave melting
curve
• melting characterized at peak maxima
• eutectic impurities may produce a second peak
melting with decomposition
• exothermic
• endothermic
eutectic melt
Thermal Analysis : Dr. A. Sedghi
Glass Transitions
• second-order transition characterized by change in heat capacity (no heat absorbed or evolved)
• transition from a disordered solid to a liquid
• appears as a step (endothermic direction) in the DSC curve
• a gradual volume or enthalpy change may occur, producing an endothermic peak superimposed on the glass transition
Thermal Analysis : Dr. A. Sedghi
Enthalpy of Fusion
157.81°C
156.50°C28.87J/g
-2.5
-2.0
-1.5
-1.0
-0.5
0.0
0.5
He
at
Flo
w (
W/g
)
140 145 150 155 160 165 170 175
Temperature (°C)
Sample: INDIUM CRIMPED PAN CHECKSize: 7.6300 mgMethod: indiumComment: P/N 56S-107
DSCFile: C:...\10C per min crimped\DSC010920A.3Operator: Ron VansickleRun Date: 20-Sep-01 09:13Instrument: 2920 MDSC V2.6A
Exo Up Universal V3.3B TA Instruments
Thermal Analysis : Dr. A. Sedghi
Burger’s Rules for Polymorphic Transitions Enantiotropy: transition is irreversible
end
otherm
ic
Heat of Transition Rule • endo-/exothermic solid-solid transition
Heat of Fusion Rule • higher melting form; lower DHf
• exothermic solid-solid transition
• higher melting form; higher DHf
Monotropy:v
end
otherm
ic
Thermal Analysis : Dr. A. Sedghi
Enthalpy of Fusion by DSC
single (well-defined) melting endotherm • area under peak • minimal decomposition/sublimation • readily measured for high melting polymorph • can be measured for low melting polymorph
multiple thermal events leading to stable melt • solid-solid transitions (A to B) from which the transition enthalpy (DHTR)
can be measured*
crystallization of stable form (B) from melt of (A)
DHfA = DHf
B - DHTR
* assumes negligible heat capacity difference between polymorphs over temperatures of interest
DHfA = area under all peaks from B to the stable melt
Thermal Analysis : Dr. A. Sedghi
Purity by DSC
• eutectic impurities lower the melting point of a eutectic system
• purity determination by DSC based on Van’t Hoff equation
• applies to dilute solutions, i.e., nearly pure substances (purity ≥98%)
• 1-3 mg samples in hermetically-sealed pans are recommended
• polymorphism interferes with purity determination, especially when a transition occurs in the middle of the melting peak
Tm = To - .
DHo
RTo2 c 1
f
melting endotherms as a function of purity.
benzoic acid
97%
99%
99.9%
Thermal Analysis : Dr. A. Sedghi
Effect of Heating Rate
• many transitions (evaporation, crystallization, decomposition, etc.) are kinetic events
… they will shift to higher temperature when heated at a higher rate
• the total heat flow increases linearly with heating rate due to the heat capacity of the sample
… increasing the scanning rate increases sensitivity, while decreasing the scanning rate increases resolution
• to obtain thermal event temperatures close to the true thermodynamic value, slow scanning rates (e.g., 1–5 K/min) should be used
DSC traces of a low melting polymorph collected at four different heating rates. (Burger, 1975)
Thermal Analysis : Dr. A. Sedghi
Effect of Phase Impurities
• Lot A: pure low melting polymorph – melting observed
• Lot B: seeds of high melting polymorph induce solid-state transition below the melting temperature of the low melting polymorph
2046742FILE# 022511DSC.1
2046742FILE# 022458 DSC.1 Form II ?
-5
-4
-3
-2
-1
0
He
at
Flo
w (
W/g
)
80 130 180 230 280
Temperature (°C)Exo Up Universal V3.3B TA Instruments
Lot A - pure
Lot B - seeds
• lots A and B of lower melting polymorph (identical by XRD) are different by DSC
Thermal Analysis : Dr. A. Sedghi
Polymorph Characterization: Variable Melting Point
• lots A and B of lower melting polymorph (identical by XRD) appear to have a “variable” melting point
-1.1
-0.9
-0.7
-0.5
-0.3
-0.1
0.1
He
at
Flo
w (
W/g
)
110 120 130 140 150 160 170 180
Temperature (°C)
DSC010622b.1 483518 HCL (POLYMORPH 1)DSC010622d.1 483518 HCL
Exo Up Universal V3.3B TA Instruments
Lot A
Lot B
• although melting usually happens at a fixed temperature, solid-solid transition temperatures can vary greatly owing to the sluggishness of solid-state processes Thermal Analysis : Dr. A. Sedghi
• the low temperature endotherm was predominantly non-reversing, suggestive of a solid-solid transition
• small reversing component discernable on close inspection of endothermic conversions occurring at the higher temperatures, i.e., near the melting point
Polymorph Characterization: Variable Melting Point
Reversing (heat flow component)
-0.50
-0.45
-0.40
-0.35
-0.30
-0.25
-0.20
-0.15
-0.10
-0.05
0.00
Re
v H
eat
Flo
w (
W/g
)
110 120 130 140 150 160 170 180
Temperature (°C)
DSC010622b.1 483518 HCL (POLYMORPH 1)DSC010622d.1 483518 HCL
Exo Up Universal V3.3B TA Instruments
Non-reversing (heat flow component)
-0.8
-0.6
-0.4
-0.2
0.0
0.2
Nonre
v H
eat F
low
(W
/g)
110 120 130 140 150 160 170 180
Temperature (°C)
DSC010622b.1 483518 HCL (POLYMORPH 1)DSC010622d.1 483518 HCL
Exo Up Universal V3.3B TA Instruments
Lot A
Lot B
Lot A
Lot B
reversing heat flow non-reversing heat flow
• the “variable” melting point was related to the large stability difference between the two polymorphs; the system was driven to undergo both melting and solid-state conversion to the higher melting form
Thermal Analysis : Dr. A. Sedghi
• development of “hyphenated” techniques for simultaneous analysis TG-DTA TG-DSC TG-FTIR TG-MS
15.55%(0.9513mg)
24.80°C100.0%
179.95°C84.45%
-1.8
-0.8
0.2
1.2
2.2
3.2
4.2
Te
mp
era
ture
Diffe
ren
ce
(µ
V/m
g)
-40
0
40
80
120
We
igh
t (%
)
20 70 120 170 220 270
Temperature (°C)
Sample: SODIUM TARTRATE (ALDRICH)Size: 6.1176 mgMethod: 25C TO 300Comment: LOT# 22411A0
TGA-DTAFile: C:\TA\Data\Sdtcal\2004\TGA040105A.5Operator: Ron VansickleRun Date: 6-Jan-04 12:09Instrument: 2960 SDT V3.0F
Exo Up Universal V3.3B TA Instruments
“Hyphenated” Techniques
• thermal techniques alone are insufficient to prove the existence of polymorphs and solvates
• other techniques should be used, e.g., microscopy, diffraction, and
spectroscopy
evolved gas analysis (EGA)
TG-DTA trace of sodium tartrate
Thermal Analysis : Dr. A. Sedghi
Thermal Expansion in one Dimension
(Length Change)
TLL o DD
change in length change in temperature
initial length
coefficient of thermal expansion (depends on the material)
Thermal Analysis : Dr. A. Sedghi
Thermal Analysis : Dr. A. Sedghi
Thermal Analysis : Dr. A. Sedghi
Thermal Analysis : Dr. A. Sedghi
Mechanical Analysis
(TMA / DMA)
A Dynamic Mechanical Analyzer (DMA) measures rheological
behavior of a sample under dynamic conditions (such as
modulus, compliance and damping) as a function of
temperature, time, frequency, stress, atmosphere or a
combination of these parameters.
A Thermomechanical Analyzer (TMA) measures dimension
changes of a sample (such as expansion or contraction) as
a function of temperature, time and force applied to the
sample.
Thermal Analysis : Dr. A. Sedghi
z
Y
X
E” ~ energy loss in
internal motion
E’ ~ elastic
response
TMA
Constant Heating Rate ◦ Initial Temp
◦ Final Temp
◦ Heating Rate (°C/min)
Data ◦ Size of Sample vs Time (or Temp.)
Measures ◦ Thermal Expansion Coefficient
◦ Volume change on crystalization or crystal transformations
◦ Sintering
◦ Glass Transitions in Polymers
Thermal Analysis : Dr. A. Sedghi
TMA
Thermal Analysis : Dr. A. Sedghi
Polymer with glass transition
DMA
Constant Heating Rate ◦ Initial Temp
◦ Final Temp
◦ Heating Rate (°C/min)
Data ◦ Force vs Time (or Temp.)
◦ Force delay vs Time (or Temp.)
◦ Viscoelastic Properties Storage and Loss Modulus
Measures ◦ Glass Transition
◦ Viscoelastic Properties
Thermal Analysis : Dr. A. Sedghi
Polymer with Glass Transition
PerkinElmer High Sensitivity Mechanical Analysis family ...
Thermal Analysis : Dr. A. Sedghi
Researc
h
Diamond TMA & DMA • Broad force range
• Multiple deformation modes
• Many measuring systems
• Dynamic & static operation
• Advanced cooling system
Thermal conductivity measurement
Thermal Analysis : Dr. A. Sedghi
Thermal Analysis : Dr. A. Sedghi
فاکتور مقاومت به شوک حرارتی
:استاندارد هاي صنعتي براي مواد ديرگداز
Thermal Analysis : Dr. A. Sedghi
1.BS standard
2.ASTM standard