Ept121 lecture 3 thermoanalytical analysis

EPT121
Analytical Polymer Chemistry
Lecturer: Mr. Kudzai Hamish Ruzvidzo
vakudzaihamish@gmail.com
Phone number - 0719121469

HIT EPT121 Lecture
Analytical Polymer Chemistry
 Thermoanalytic methods
 Thermogravimetric Analysis (TGA)
 Differential Scanning Calorimetry (DSC)
 Thermo Mechanical Analysis (TMA)
 Dynamic Mechanical Analysis (DMA)
 Differential Thermal Analysis (DTA)

Introduction to Thermal Analysis (TA)
 Thermal analysis (TA) has been defined as “a group of techniques in
which a physical property of a substance and/or its reaction products is
measured as a function of temperature while the substance is subjected
to a controlled temperature programme”
 Thermal analysis (TA) is a branch of materials science where the
properties of materials are studied as they change with temperature.
 There are several methods used commonly and are distinguished from
each other by the property which is measured:

 Differential thermal analysis (DTA) -
measures the difference in temperature
 Differential scanning calorimetry (DSC) -
measures the heat difference
 Thermogravimetric analysis (TGA) -
measures change in mass
 Dynamic mechanical analysis (DMA):
mechanical stiffness and damping
 Thermomechanical analysis (TMA):
dimension

 The most common thermal analysis techniques for polymers are: differential
scanning calorimetry (DSC), Thermogravimetric analysis (TGA),
thermomechanical analysis (TMA), and dynamic mechanical analysis (DMA).
 In DSC a sample is heated, cooled, or held at a constant temperature as heat
flows to and from the sample.
 The reference material is measured as a function of temperature.
 The measurement is the amount of energy absorbed and released by the
sample in milliwatts.
 The sample is heated, cooled, or held isothermally in a defined atmosphere,
and its mass is weighed in TGA.
 In TMA a sample is measured as a function of temperature in terms of its
abilities to deform or change as it is being subjected to a constant force, an
increasing force, or a modulated force.
 DMA requires the sample to be subjected to a periodically oscillating force,
and its mechanical properties are assessed. Specifically, its force amplitude,
displacement (deformation) amplitude, and phase shift are determined as a
function of temperature or frequency.

 Of these major thermal analysis techniques, DSC is seen as the most
versatile in the evaluation of various aspects of materials whether the
criteria is heat capacity, melting qualities including melting point,
vaporization, crystallization, temperature stability, elasticity, glass
transitioning qualities, or oxidative degradation.

Thermogravimetry of Polymers
 Definition: Thermogravimetric Analysis is a technique in which the mass
of a substance is monitored as a function of temperature or time as the
sample specimen is subjected to a controlled temperature program in a
controlled atmosphere.
 An Alternate Definition: TGA is a technique in which, upon heating a
material, its weight increases or decreases.
 A Simple TGA Concept to remember: TGA measures a sample’s weight
as it is heated or cooled in a furnace.

TGA: The Technique
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.

Differential Thermal
analysis (DTA)
- Measure temperature
difference between the
sample and reference.
Differential Scanning
Calorimetry (DSC)
– Measure heat
absorbed or liberated
during heating or
cooling
Thermal Gravimetric
Analysis (TGA)
– Measure change in
weight during heating
or cooling
Thermal Analysis

Thermogravimetric analysis (TGA)
Monitor change in mass of sample

Sample:
can be both solid &liquid;
2-25 mg
Gas atmosphere:
CaCO3 →CaO + CO2
In vacuum, decompose at ~500ºC
In air, decompose at ~700ºC
In CO2, ~900ºC

Mechanisms of Weight Change in TGA
• Weight Loss:
• Decomposition: The breaking apart of chemical bonds.
• Evaporation: The loss of volatiles with elevated temperature.
• Reduction: Interaction of sample to a reducing atmosphere (hydrogen,
ammonia, etc.)
• Desorption: a phenomenon whereby a substance is released from or
through a surface
• Weight Gain:
• Oxidation: Interaction of the sample with an oxidizing atmosphere.
• Absorption: process by which a substance incorporated in one state is
transferred into another substance of a different state
All of these are kinetic processes (i.e. there is a rate at which they occur).

Instrumentation
 The instrument used is a thermobalance
 A TGA consists of a sample pan that is supported by a precision
balance.
 That pan resides in a furnace and is heated or cooled during the
experiment.
 The mass of the sample is monitored during the experiment.
 A sample purge gas controls the sample environment.
 This gas may be inert or a reactive gas that flows over the sample and
exits through an exhaust.

Thermobalance
 The apparatus used for obtaining TG (thermograms)
curves is referred to as a thermobalance. It consists
of a continuously recording balance, furnace,
temperature, programmer and a recorder
 The balance mechanism itself is usually of the null-
deflection type to ensure that the sample's position
in the furnace will not change.
 The balance transmits a continuous measure of the
mass of the sample to an appropriate recording
system, which is very often a computer.
 The resulting plot of mass vs. temperature or time is
called a TC curve.

Applications
 The information provided by TG is confined to the detection of changes
in mass of the sample as its temperature is altered.
 Thus the technique is largely limited to the study of decomposition and
oxidation reactions and to such physical processes as vaporization,
sublimation and desorption

(i) No decomposition with loss
of volatile products.
(ii) Rapid initial mass loss
characteristic of desorption or
drying.
(iii) decomposition in single
stage.
(iv) multi-stage decomposition.
(v) multi-stage decomposition
but no stable intermediates.
(vi) Gain in mass as a result of
sample reaction.
(vii) reaction product
decompose again.

Thermal Stability Assessment and Compositional Analysis
 The assessment of thermal stability is one of the most important
applications of TG to the study of polymers.
 Thermogravimetric curves provide information about the decomposition
mechanisms for various materials.
 In addition, the decomposition profiles may be characteristic for each type
of polymer and in some cases can be used for identification purposes.
 The onset of mass loss often defines the upper limit of thermal stability for
the material, though it must be appreciated that extensive degradation of
the polymer structure by, for example, cross-linking, may have already
taken place before the point at which detectable changes in mass occur.

The routes by which polymers degrade can be categorized
according to six main mechanisms:
1. main-chain scission
2. side group scission
3. elimination
4. depolymerisation
5. cyclization
6. Cross-linking.
Cyclization and cross-linking rarely result in any change of sample mass
unless they occur in conjunction with 1–4 and are not detected by TG.

 Routes 1–4 usually result in the evolution of volatile products with an
accompanying mass change.
 In an inert atmosphere, some polymers give an almost quantitative yield
of their parent monomers.
 In air, complete oxidation of the sample to oxides of its constituent
elements commonly occurs.
 Nitrogen containing polymers usually generate some ammonia or
hydrogen cyanide.
 Halogen-containing polymers yield the respective hydrogen halides

Draw tangents of the curve to find the onset and the offset points

Thermal profiles for some common polymers
PVC
PMMA
PTFE
PI

• PVC is the least thermally stable.
• Polymer (PI) is the most thermally stable
• Polymer (PI) looses no weight at all below about
500 degrees Celsius and then decomposes
abruptly at about 600 degrees Celsius.
• The three other polymers all have decomposed
by about 450 degrees Celsius.
• Polymers (PMMA) decomposes more slowly
overall than the others as indicated by slopes of
TG curves.
• TG curve of polymer (PMMA) has less slope
than the others.
• The PVC starts degradation at lower
temperature ~150 degrees Celsius and takes
place in two steps.

Three factors should be noted when you get a TG curve:
1. General shape,
2. The particular temperatures at which changes in mass occur
(severely affected by many experimental conditions),
3. The magnitudes of the mass changes (much more use
directly related to the specific stoichiometries of the
reactions, independent of the many factors that affect the
shape of the curves. Can be used for precise quantitative
analysis).

 Figure 1 shows a series of Thermogravimetric
curves for a number of common polymers in
nitrogen.
 When comparing the thermal stability of polymers
it must be noted that such curves are purely
procedural.
 For meaningful correlation of thermal stability
with polymer structure it is essential that the
experiments are carried out under similar
experimental conditions.
 It is usual to assign a temperature at which
degradation begins to occur (e.g. the extrapolated
onset of the lowest temperature weight loss) or
quote the temperature at which (for example) 5%
weight loss has taken place.
 Often, significant deterioration in polymer
properties has occurred below these values.

 The information provided by TG is inherently quantitative.
 Provided that the temperature scale is accurately
calibrated and the balance provides an output
proportional to the mass of the sample across its
operating range, then the mass loss profile of a mixture of
materials is usually the sum of the individual profiles of
each of its components.
 This affords a means of compositional analysis of materials
such as polymer blends and composites.
 An example of this is shown in Figure 2 for carbon
fiber/epoxy composite.
 In this case, the sample was heated to 825 °C in an inert
atmosphere so that degradation of the epoxy resin took
place.
 Then the furnace was purged with air so that oxidation of
the carbon fiber took place.
 The percentage composition of each component in the
specimen can be determined after due allowance has
been made for any carbonaceous residue arising from
degradation of the epoxy resin.

 Figure 1 shows the TGA results generated on
nylon 6,6 toothbrush bristles.
 The plot shows the percent mass as a function
of sample temperature for the nylon 6,6
bristles under a nitrogen purge.
 Approximately 10 mg of sample was heated at
a rate of 20 C/min with the PerkinElmer TGA.
 The TGA results show that the nylon 6,6
polymer undergoes thermal degradation
beginning at 482 C and with a total mass loss
of 99.0%.
 There is a small amount of inert residue
remaining (0.15%).

 Nylon polymers absorb a small amount of
ambient moisture and TGA can be used to
determine this level of water.
 This may be seen in Figure 2 for the nylon 6,6
sample, which is an enlarged view of the TGA
results in the temperature region below the
onset of degradation.
 At about 56 C, the nylon polymer starts to evolve
the small amount of moisture, which is found to
be 0.86% by TGA.
 A high performance TGA instrument is required
to detect this small level of moisture content.
 Knowing this moisture content is important as it
has a major bearing on the end use properties
and processing performance of nylon.

Filler Content in Polymers
 One major application of TGA is the
assessment of the filler content in polymers
and composites.
 The level of fillers can have a significant
impact on the end use properties (thermal
expansion, stiffness, damping) of the final
product.
 This is particularly important for electronics
applications where the level of filler affects
the coefficient of thermal expansion (CTE) as
measured using the PerkinElmer TMA.
 It is important for the components in a
printed circuit board to have very similar
expansivities or else built-in stresses over
time can occur.
 Displayed in Figure 3 are the TGA results
generated on a glass filled epoxy resin used
for electronic applications.

TG Curves of some polymers: PVC = polyvinyl chloride; PMMMA = polymethyl
methacrylate, LDPE = low density poly ethylene; PTFF = polytetra fluoroethylene;
and PS = polystyrene.
• TG Curves clearly indicate that
polymer (PVC) is the least thermally
stable and polymer (PS) is most
thermally stable.
• Polymer (PS) looses no weight at all
below about 500o C and then
decomposes abruptly by about 600 o C.
• The other three polymers have all
decomposed by about 450 o C.
• Polymers (PMMA) decomposes more
slowly overall than the others as
indicated by slopes of TG curves.
• TG curve of polymer (PMMA) has
less slope than the others.

• The polymer starts degradation at
the extrapolated on set of the lowest
temperature mass loss or quote the
temperature at which 5% mass loss
has taken place.
• The PVC starts degradation at
lower temperature ~ 150 °C and
takes place in two steps while
NYLON -6 , LDPE and PTFE start
degrading at higher temperatures
400 °C , 450 °C and 550 °C
respectively and in single steps.
• Qualitatively, the higher the
decomposition temperature, the
more positive is the ∆G value at
room temperature and the greater
the stability.
• This can predict the relative
stability of the polymers.

Case study - DEVELOPMENT OF GINGER REINFORCED POLYVINYL ALCOHOL
BIOCOMPOSITES (Ruzvidzo, 2018)
• Thermogravimetric analyses of the ginger
reinforced polyvinyl alcohol biocomposites was
performed using a Thermogravimetric analyzer
(PerkinElmer Pyris-6).
• They measure the changes in the mass of a
sample as a function of the temperature.
• The experiments were carried out under
nitrogen atmosphere by heating the biocomposite
samples in an aluminum crucible at 10oC/min
from 40oC to 800oC.

Figure 4.10 shows the weight percentage vs sample temperature of the PVA sample.
Figure 4.11 shows the weight percentage vs sample temperature of the ginger
reinforced polyvinyl alcohol biocomposite. The TGA curves of both pure PVA
samples and PVA/ginger showed three weight loss stages
-4
-3.5
-3
-2.5
-2
-1.5
-1
-0.5
0
0.5
1
0
10
20
30
40
50
60
70
80
90
100
0 100 200 300 400 500 600 700 800
DerivativeWeight%(%/min)
Weight%(%)
Temperature (degrees celcius)
TGA plot for pure PVA
Weight % Derivative Weight %
-5
-4
-3
-2
-1
0
1
2
0
10
20
30
40
50
60
70
80
90
100
0 100 200 300 400 500 600 700 800
Weight%(%)
TGA plot for biocomposite sample

• For the pure PVA sample, the initial weight loss occurred
at temperature region of 40 to 110°C due to the evaporation
or loss of moisture from the polymer matrix.
The loss in weight was about 5.88wt% in this stage.
• The major loss of weight occurred in the 150 to 380°C.
This is because of the degradation of the side chain i.e. O-H
groups of the PVA.
The loss of weight in stage was about 55wt%.
• The third stage ranged from temperatures above 400°C
and corresponded to the cleavage or breakdown of the C–C
backbone of the polyvinyl alcohol.
The weight loss in this stage was around 30%.
The degradation temperature of the PVA sample was 290oC.
-4
-3.5
-3
-2.5
-2
-1.5
-1
-0.5
0
0.5
1
0
10
20
30
40
50
60
70
80
90
100
0 100 200 300 400 500 600 700 800
Weight%(%)
TGA plot for pure PVA

• The PVA/ginger biocomposites also exhibited three major stages of
weight losses.
• The initial weight loss occurred in the region from region 40 to 110°C
and was due to the loss of moisture in the biocomposites.
The weight loss was about 4.16wtpercentage.
• The greatest weight loss occurred from temperatures of 160 to 400oC
and this was due to the structural degradation of the PVA matrix in the
biocomposites.
The weight loss at this stage was about 52wt%.
• The third stage was for temperatures above 400oC and it corresponds
to the cleavage or breakdown of the backbone of PVA as well as the
degradation of fibre.
• The degradation temperature of the PVA/ginger biocomposite sample
was 310oC.
-5
-4
-3
-2
-1
0
1
2
0
10
20
30
40
50
60
70
80
90
100
0 100 200 300 400 500 600 700 800
Weight%(%)
TGA plot for biocomposite sample

Thermal Analysis
Differential Scanning Calorimetry (DSC)

Introduction• The technique was developed by E.S.
Watson and M.J. O'Neill in 1960, and
introduced commercially at the
Pittsburgh Conference on Analytical
Chemistry and Applied Spectroscopy
in 1963
• More common than TGA technique
• This technique is used to study what
happens to polymers/samples upon
heating
• It is used to study thermal transitions
of a polymer/sample (the changes
that take place on heating)
For example:
The melting of a crystalline polymer
The glass transition
The crystallization

DSC: Definitions
 A calorimeter measures the heat into or out of a sample.
 A differential calorimeter measures the heat of a sample
relative to a reference.
 A differential scanning calorimeter does all of the above
and heats the sample with a linear temperature ramp.
 Endothermic heat flows into the sample.
 Exothermic heat flows out of the sample.

• Amorphous phase – The portion of material whose molecules are randomly oriented in space. Liquids
and glassy or rubbery solids. Thermosets and some thermoplastics
• Crystalline phase – The portion of material whose molecules are regularly arranged into well defined
structures consisting of repeat units. Very few polymers are 100% crystalline.
• Semi-crystalline Polymers - Polymers whose solid phases are partially amorphous and partially
crystalline. Most common thermoplastics are semi-crystalline.

• Melting – The endothermic transition upon heating from a crystalline solid to
the liquid state. This process is also called fusion. The melt is another term
for the polymer liquid phase.
• Crystallization – The exothermic transition upon cooling from liquid to
crystalline solid. Crystallization is a function of time and temperature.
• Cold crystallization – The exothermic transition upon heating from the
amorphous rubbery state to the crystalline state. This only occurs in semi-
crystalline polymers that have been quenched (very rapidly cooled from the
melt) into a highly amorphous state.
• Enthalpy of melting/crystallization – This is calculated by integrating the
area of the DSC peak on a time basis.

• Semi-crystalline polymers have both crystalline
and amorphous regions.
• Semi-crystallinity is a desirable property for
most plastics because they combine the
strength of crystalline polymers with the
flexibility of amorphous.
• Semi-crystalline polymers can be tough with an
ability to bend without breaking.
• If we model a polymer as having distinct
crystalline and amorphous regions then the
percentage of the polymer that is crystalline is
called the percent crystallinity. The percent
crystallinity has an important influence on the
properties of the polymer.

What DSC can tell you
• Glass transitions
• Melting and boiling points
• Crystallization time and temperature
• Percent crystallinity
• Heats of fusion and reactions
• Specific heat
• Oxidative/ Thermal stability
• Rate and degree of cure
• Reaction kinetics
• Purity

Principle
• It is a technique in which the energy necessary to establish a zero temperature difference
between the sample & reference material is measured as a function of temperature.
• Here, sample & reference material are heated by separate heaters in such a way that
their temp are kept equal while these temp. are increased or decreased linearly.
• During heating two types of reactions can be take place one is the endothermic
and the other is the exothermic.
• Endothermic reaction:
If sample absorbs some amount of heat during phase transition then reaction is said to be
endothermic
Inendothermic reaction more energy needed to maintain zero temp difference between sample &
reference.
E.g. Melting, boiling, sublimation, vaporization
• Exothermic reaction:
if sample released some amount of heat during phase transition, then reaction is said to be
exothermic.
In exothermic reaction, less energy needed to maintain zero temp difference between sample &
reference.
E.g crystallization, degradation, polymerization

Differential scanning calorimetric (DSC)
Differential scanning calorimetry or DSC is a thermoanalytical
technique in which the difference in the amount of heat required to increase
the temperature of a sample and reference are measured as a function of
temperature.
DTA DSC

What happens to a polymer when heated?
• The polymer is heated in a device that looks
something like this:
• There are two pans, In
sample pan, polymer is
added, while the other,
reference pan is left empty
• Each pan sits on top of
heaters which are
controlled by a computer
• The computer turns on
heaters, and let them heat
the two pans at a specific
rate, usually 10oC/min
• The computer makes
absolutely sure that the
heating rate stays exactly
the same throughout the
experiment

Why heaters don’t heat at the same rate?
• The simple reason is that the two pans are different.
• One has polymer in it, and one doesn't.
• The polymer sample means there is extra material in the sample pan.
• Having extra material means that it will take more heat to keep the temperature
of the sample pan increasing at the same rate as the reference pan
• So the heater underneath the sample pan has to work harder than the heater
underneath the reference pan.
• It has to put out more heat.
• How much more heat it has to put out is what measured in DSC experiment?
• Specifically, a plot is drawn as the temperature increases.
• The temperature is taken on x-axis whist the difference in heat output of the two
heaters at a given temperature on y-axis

DSC Heat Flow
t)(T,
dt
dT
Cp
dt
dH
f
signalflowheatDSC
dt
dH

WeightSampleHeat xSpecificSample
CapacityHeatSampleCp


RateHeating
dt
dT

(kinetic)retemperatuabsoluteanat
timeoffunctionisthatflowHeatt)(T, f

DSC: Calculation of % Crystallinity

Differential thermal analysis (DTA)

Differential thermal analysis (DTA)
 DTA involves heating or
cooling a test sample and an
inert reference under identical
conditions, while recording
any temperature difference
between the sample and
reference.
 This differential temperature is
then plotted against time, or
against temperature.
 Changes in the sample which
lead to the absorption or
evolution of heat can be
detected relative to the inert
reference.

• Differential thermal analysis (or DTA) is a
Thermoanalytic technique that is similar to
differential scanning calorimetry.
• DTA consists of heating a sample and reference
material at the same rate and monitoring the
temperature difference between the sample and
reference.
• In this method, the sample is heated along with a
reference standard under identical thermal
conditions in the same oven.
• The temperature difference between the sample
and reference substance is monitored during the
period of heating.
• As the samples undergo any changes in state, the
latent heat of transition will be absorbed/ evolved
and the temperature of the sample will differ from
that of the reference material.
• This difference in temperature is recorded.
• Hence, any change in state can be detected along
with the temperature at which it occurs.

Differential Thermal analysis (DTA)
» Measure sample temperature relative to a reference, for the
same heat transferred
Thermal events: Exothermic event and endothermic event
Reaction/decomposition, Melting, Crystallization, Change in crystal structure
Glass transition

Introduction
• DTA involves heating or cooling a test sample and an inert reference
under identical conditions, while recording any temperature
difference between the sample and reference.
• This differential temperature is then plotted against time, or against
temperature.
• Changes in the sample which lead to the absorption or evolution of
heat can be detected relative to the inert reference.
• DTA may be defined formally as a technique for recording the
difference in temperature between a substance and a reference
material against either time or temperature as the two specimens are
subjected to identical temperature regimes in an environment heated
or cooled at a controlled rate.

Description of the Method
• DTA measures the differential temperature between a sample and a
reference pan, which are closely matched thermally and arranged
symmetrically within the oven.
• As the sample goes through the programmed dynamic temperature
change, there is no temperature difference until the sample
undergoes an exothermic or endothermic chemical reaction or
change of physical state.
• In the case of an exotherm, the sample’s temperature will increase,
while in the case of an endotherm, it will decrease.
• In either case, the thermal event will be recorded as the sample
temperature departs from the baseline and then returns to the base
line when the reaction or transformation is complete.

• Also, a change in the heat capacity of the sample will show as a
change in slope (e.g. Glass Transition (qv)) in the T versus time
or temperature plot.
• Modern DTA instruments generally use matched
thermocouples as sensors, one each in contact with the sample
or its container and the reference material or its container.
• The output of the differential signal is amplified and sent to a
data acquisition system.

Applications of DTA for Polymers
Table above describes some of the many applications of DTA and DSC.

• Both DTA and DSC can be used to determine the temperature
of the transitions, cited in Table 2.
• However, the DSC peak area, in addition, gives quantitative
calorimetric information (heat of reaction, transition, or heat
capacity).
• DTA can only do so when calibration with a standard material
allows the quantitative conversion of T to heat flow and,
ultimately, heat of transition (H) or heat capacity (Cp).
• Also, the response of DTA with increasing temperature may be
affected by poor heat transfer in the system, detector sensitivity,
etc.
• For these reasons, when there is a choice between DSC and
DTA, DSC is the preferred method.

STUDENT ACTIVITY
Compare and contrast the techniques of
Differential Scanning Calorimetry (DSC) and
Differential Thermal Analysis. (DTA)
Similarities
Differences
Advantages
Disadvantages

• In Differential Thermal Analysis, the
temperature difference that develops
between a sample and an inert reference
material is measured, when both are subjected
to identical heat - treatments.
• The related technique of Differential Scanning
Calorimetry relies on differences in energy
required to maintain the sample and reference
at an identical temperature.

Apparatus
• A DTA consists of a sample holder, thermocouples, sample containers
and a ceramic or metallic block; a furnace; a temperature
programmer; 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 Al2O3, while
the other is placed in a sample of the material under study.
• As the temperature is increased, there will be a brief deflection of the
voltmeter if the sample is undergoing a phase transition.
• This occurs because the input of heat will raise the temperature of
the inert substance, but be incorporated as latent heat in the material
changing phase

Dynamic mechanical analysis(DMA)

Dynamic mechanical analysis (DMA) is a technique used to study
and characterize materials.
It is most useful for studying the viscoelastic behavior of polymers.
A sinusoidal stress is applied and the strain in the material is
measured, allowing one to determine the modulus.
• The temperature of the sample or the frequency of the stress are
often varied, leading to variations in the modulus.
• This approach can be used to locate the glass transition
temperature of the material.
Dynamic mechanical analysis

Characterize Visco-Elastic properties.
Storage Modulus E’ (elastic response) and Loss Modulus E’’
(viscous response) of polymers are measured as a function of T
or time as the polymer is deformed under an oscillatory load
(stress) at a controlled (programmed) T in specified atmosphere.
• DMTA can be applied to determine the glass transition of
polymers or the response of a material to application and
removal of a load.

Stiffness is the extent to which an object resists deformation in response to an applied force.
Stiffness of plastic is the ability of the material to distribute a load and resist deformation or deflection (functional failure).

A typical DMA tester with grips to hold sample and environmental chamber to
provide different temperature conditions. A sample is mounted on the grips and the
environmental chamber can slide over to enclose the sample.

DMA measures stiffness and damping, these are reported as modulus and tan
delta. Because sinusoidal stress is applied, modulus can be expresesed as;
• in-phase component, the storage modulus (E‘) and
• out of phase component, the loss modulus (E")
Storage modulus (E‘) is a measure of elastic response of a material. It measures
the stored energy.
Loss modulus (E") is a measure of viscous response of a material. It measures the
energy dissipated as heat.

Ept121 lecture 3 thermoanalytical analysis

Ept121 lecture 3 thermoanalytical analysis

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