Dynamic mechanical properties refer to the response of a material as it is subjected to a periodic force. These properties may be expressed in terms of a dynamic modulus, a dynamic loss modulus, and a mechanical damping term.

2. Under the Guidance of:
Dr. Pradip K. Maji

3. Dynamic MechanicalAnalysis
Or
DMA
What is it and
what’s it all about?

4. Dynamic mechanical analysis (abbreviated DMA, also known
as dynamic mechanical spectroscopy) is a technique used to
study and characterize materials.
Dynamic Mechanical
Analysis measures the
mechanical properties of
materials as a function of
time, temperature, and
frequency.

5. The DMAlets you relate
MATERIAL
BEHAVIOUR
Product PropertiesMolecular Structure
Processing
Conditions

6. Hmm…
Seems Interesting..
let’s know aboutit
more deeply

7. Whatare DynamicMechanical Properties ?
Dynamic mechanical properties refer to the
response of a material as it is subjected to a
periodic force. These properties may be expressed
in terms of a dynamic modulus, a dynamic loss
modulus, and a mechanical damping term.
Typical values of dynamic modulus for polymers range from 106 -1012 dyne/cm2 depending upon the
typeofpolymer,temperature,andfrequency.

8. DYNAMIC MECHANICAL
ANALYZER
But
How to analyze
these properties ?

9. >> DMA is a measuring instrument which is used to determine
the dynamic characteristics of materials.
>> It applies a dynamic oscillating force to a sample and analyze
the material’s response to that cyclic force.
>> Basically, DMA determines changes in sample properties
resulting from changes in five experimental variables:
TEMPERATURE TIME FREQUENCY FORCE STRAIN

11. how it
works???

12. Preparation of Specimen
 Depending on the material to analyze, the
specimen can be prepared in different ways:
Molding, Cutting
 As a general rule, common specimen
dimensions range from a few millimeters to
a few centimeters. The use of a caliper is
then advised. The use of a micrometer is
preferred to measure film thickness.

13. Compression plates
Tension jaws for film
Tension jaws for bars Tension jaws for bars
Plane shear for films
Plane shear
Shear for liquid Shear for pasty material
Dual cantilever Three point bending
Configuration of specimen and
specimen holder for different
tests in DMA

14. 3. Installationofthe selectedspecimen holder
4. Installationofthe preparedspecimen intothespecimen holder inside thermalchamber
5. Starttemperature,finishtemperature,andstep
6. Applicationofdynamicexcitation(stress orstrain)onthe specimen bydynamicshakerthrough
entiretemperaturerange
7. ThenDMA recordsthe responseof specimen and
determines:E’, E”, Tan
8. Identifytransitiontemperaturesbasedonnoticeablechanges in curves

16. Result
Storage modulus
(E’):elastic property
 Loss modulus
(E”) :viscous property
 Loss tangent (tan )
A typical response from a DMAshows both modulus and Tanδ. As the material goes through its glass transition, the
modulus reduces andthe Tanδ goes through a peak.
 Tg indicated by majorchange in curves: Largedropin log E’ curve andPeak in Tanδ curve

17. THEORITICAL
BASIS

18. Viscoelasticity :-
Viscoelastic materials exhibit
characteristics of both viscous
and elastic materials
Ex.- Elastomers, polymers etc.
Glass Transition Temperature
Definition: Transition from bond
stretching to long range
molecular motion
Theoretical basis for DMA
Elastic vs ViscoelasticViscosity  resistance to flow (damping)
Elasticity  ability to revert back to original shape
Flow Temperature
Definition: point at which heat vibration is enough to break bonds in crystal lattice

19.  sinusoidally applied stress
 measured strain
  phase lag between applied stress and measured strain
 Complex dynamic modulus (E*)
• Ratio of applied stress to measured strain
E* = E’ + iE” = SQRT(E’2+ E”2)
 Storage modulus (E’)
• Energy stored elastically during deformation
• “Elastic” of “viscoelastic”
• E’= E* cos 
 Loss modulus (E’’)
• Energy loss during deformation
• “Visco” of “viscoelastic”
• E” = E* sin 
 Loss tangent (tan ) or damping or loss factor
• shows the ability of material to dissipate the energy
• Tan = E’’/E’

20.  If phase lag  is zero
then E*= E’  material is purely elastic
 If phase lag  is 90 degree
then E* = E”  material is purely viscous
 If phase lag  is between 0  90 degree
then E* = E’ + iE”  material is viscoelastic

21. Determination
of different
Moduli
And their
application

22. Let’s see and understand
What are Storage Modulus, Loss
Modulus and Tan δ……

24.  Oscillationandresponseof alinear-viscoelasticmaterial;δ =
phaseangle, E =tensile modulus,G =shearmodulus,K= bulk
compressionmodulus,L =uniaxial-strainmodulus
 ֽThe complexmodulusE*is theratioof thestressamplitudeto
the strainamplitudeandrepresentsthe stiffnessofthe
material.The magnitudeofthe complexmodulusis

25. These are dynamic elastic characteristics and are material-specific; their magnitude depends
criticallyon thefrequencyaswell asthemeasuringconditionsandhistoryofthespecimen.
the storage modulus E´ represents the stiffness of a visco- elastic material and is proportional to
the energy stored during a loading cycle. It is roughly equal to the elastic modulus for a single,
rapidstressatlow loadandreversible deformation.
the loss modulus E´´ is defined as being proportional to the energy dissipated during one loading
cycle. It represents, for example, energy lost as heat, and is a measure of vibrational energy that
hasbeen convertedduringvibrationandthatcannotberecovered.
modulusvaluesareexpressedin MPa,butN/m2aresometimes used.
The phase angle δ is the phase difference between the dynamic stress and the dynamic strain in
a viscoelastic material subjected to a sinusoidal oscillation. The phase angle is expressed in
radians(rad).

26. The loss factor tan  is the ratio of
loss modulus to storage modulus.
It is a measure of the energy lost,
expressed in terms of the recover-
able energy and represents mech-
anical damping or internal friction
in a visco-elastic system. The loss
factor tan  is expressed as a
dimensionless number. A high tan  value is indicative of a material that
has a high, non elastic strain component, while a low value indicates one
that is more elastic.
In a purely elastic material the stress and deformation are in phase ( = 0),
that is, the complex modulus E* is the ratio of the stress amplitude to the
deformation amplitude and is equivalent to the storage modulus E´ ( = 0,
therefore cosine 0 = 1; sine 0 = 0, therefore E* = E´). Steel is an example of
an almost purely elastic material. In a purely viscous material, such as a
liquid, the phase angle is 90°. In this case, E* is equal to the loss modulus
E´´, the viscous part.

27. Determining the glass transition temperature from the
maximum loss tangent is fairly straightforward. Furthermore, the
value agrees well with the temperature given by DMA step
evaluation (linear plot, half height). Problems can arise,
however, if the loss modulus maximum is not sufficiently
accentuated.
In summary, it may be said that different methods of
determining Tg yield different values for Tg. When a glass
transition temperature is stated, therefore, it is absolutely vital
to indicate the method of evaluation in addition to the
experimental parameters.

28. Which materials can be analyzed with DMA ?
DMA instrumentcan be used to characterizemechanical and/orthermal properties of a great numbers of materials:
Polymers
Elastomers
Composites
Metals and alloys
Ceramics, glass
Adhesives
Bitumen
Paint and varnish
Cosmetics
Oils
Biomaterials
Leather, skin hair….

29. APPLICATIONS
OF
D.M.A.

30.  Measurement of the glass transition
temperature of polymers
 Varying the composition of monomers
 Effectively evaluate the miscibility of polymers
 To characterize the glass transition
temperature of a material

31. This table shows which DMA characteristics can be used to describe quality
defects, processing flaws, and other parameters.
Application Charachteristic Example
Regions in which state is
dependent on
temperature
E‘ Energy and entropy-elastic
region, start of melting
Temperature-dependent
stiffness
E´, E´´, Tg , tan δ Elastic and non elastic
response
Thermal limits on use Tg Start of softening or
embrittlement
Frequency and
temperature dependent
damping
tan δ (f) Response of damping
elements

32. Application Charachteristic Example
Blend of constituents difficult
to identify by DSC
Tg Impact-modification of
Polyamid 6 through
butadiene rubber
Influence of fiber
reinforcement on mechanical
parameters
E´, E´´, tan G Anisotropic stiffness
Recycling, repeated
processing, aging
T g1 , Tg2 Shift in butadiene Tg from
ABS to higher temperatures
State of aging (conditioning) Tg Water content of PA
Degree of curing, postcuring Tg Tg rises, tan G falls, modulus
rises
Thermal degradation Tg Tg falls

33. Thank you!
Source:
 MAC.IASTATE.EDU GUIDE
 WWW.WIKIPEDIA.ORG
 TAINSTRUMENTS DMA+450 MODEL GUIDE
 WWW.PERKINELMER.COM
 WWW.SCHOLAR.LIB.VT.EDU
 DMA: A PRACTICAL INTRODUCTION
by Hevin P. Menard