Thermal analysis of Polymer , DSC, TGA , DTA , TMA , principle and mechanism

1. Bharati vidyapeeth university
poona college of pharmacy
THERMAL
CHARACTERIZATION OF
POLYMERS

2. Content
 Polymer characterization technique.
 General terms of Thermodynamics.
 Thermal behavior of
polymers(Tg,Tm,Tc).
 Technique of Thermal characterization
 DSC,
 DTA,TGA,TMA.
 Reference.

3. POLYMER AND POLYMER
MORPHOLOGY
 Polymers are large macromolecules consisting of
repeating structural units.
 The morphology of most polymers is semi-
crystalline. That is, they form mixtures of small
crystals and amorphous material and melt over a
range of temperature instead of at a single melting
point.
 Thermoplasts : Polymers soften when heated and
harden when cooled.
 Thermosets: These polymers become
permanently hard when cooled. They do not soften
during subsequent heating.

4. Polymer characterization
Techniques
 Chemical Properties .
 Thermal Properties.
 Rheological Properties.
 Morphology.
 Mechanical and dielectric properties.

5. Thermal Analysis/ Characterization
 The term thermal analysis (TA) is
frequently used to describe analytical
experimental techniques which investigate
the behaviour of a sample as a function of
temperature.
 IUPAC definition - a group of techniques in
which a physical property is measured as
a function of temperature, while the
sample is subjected to a controlled
temperature programme.

6. Types of Thermal analytical techniques
THERMAL TECHNIQUE PROPERTY USES
Thermogravimetry
(TG)
Mass Decomposition,
oxidation reactions
Differential Thermal
Analysis (DTA)
Temperature
difference
Phase change
reactions
Differential Scanning
Calorimetry (DSC)
Heat flow Heat capacity, phase
change reactions
Thermo mechanical
Analysis (TMA)
Deformations Softening, Expansion
Dynamic mechanical
Analysis (DMA)
Deformations Phase changes
Di-electrical Thermal
Analysis (DETA)
Electrical Phase changes

7. General terms of Thermodynamics
 Temperature : it is the average kinetic energy of
the atoms or molecules of the system.
 Heat : Heat is a form of energy, which in
spontaneous processes flows from a higher -
temperature body to a lower - temperature body.
 heat flow can be defined as a process in which
two thermodynamic systems exchange energy. The
flow of heat continues until the temperature of the
two systems or bodies becomes equal. This state
is called thermal equilibrium
 There are three major forms of heat flow:
 conduction, convection, and thermal radiation

8.  Latent Heat :The latent ( “ hidden ” ) heat is the
amount of heat absorbed or emitted by a material
during a phase transition. the current term is the
heat of transition
 Enthalpy: Enthalpy is the measurement of energy
in a thermodynamic system. The quantity of
enthalpy equals to the total content of heat of a
system,
H ≡ U + pV
 H is the enthalpy SI unit Joule.
 Entropy : The measure of the level of disorder in a
closed but changing system, a system in which
energy can only be transferred in one direction
from an ordered state to a disordered state

9.  Heat Capacity : Heat capacity indicates how much
heat is needed to increase the sample temperature
by 1°C. The heat capacity of a unit mass of a
material is called specific heat capacity . The SI
units for heat capacity are J/(K · mol) or J/(K · kg).

10.  Crystallisation Temperature :( Tc)
When polymers fall into these crystalline
arrangements, they give off heat to the system, thus
the process is exothermic. In fact the heat flow drops
as one can note from the big dip in the plot of (q/t) vs.
T

11.  Glass Transition Temperature:
A glass transition temperature (Tg) is the temperature
above which material changes from a hard and
relatively brittle "glassy" state into a viscous or
rubbery state as the temperature is increased. Each
polymer with an amorphous structure has its own
unique glass transition temperature.

12.  Melting Point : The melting point ( Tm ) is the
temperature at which a crystalline solid changes to
an isotropic liquid. Upon melting the polymers
absorb heat, thus melting is an endothermic
transition. From a DSC curve the melting point of a
low molecular mass, high - purity substance can be
determined as the point of intersection of the
leading edge of the melting peak with the
extrapolated baseline.
 This determination of the melting point is not
suitable for low - molecular - mass substances of

13. Differential Scanning Calorimetry
 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 is measured as a function of temperature
 These measurements provide quantitative and
qualitative information about physical and chemical
changes that involve endothermic or exothermic
processes, or changes in heat capacity.

14.  Involves general measurement of heat flow in and
out of the system i.e. endothermic and exothermic
reaction.
 Endothermic reaction on a DSC occurs from:
1. Melting
2. Glass transitions
3. Decompositions (rarely)
 Exothermic reaction measured by DSC is
indicative of:
1. Condensation
2. Molecular reorganizations like crystallization.

15. Types of DSC:
HEAT FLUX DSC :
 Here the difference in heat
flow into the sample and
reference is measured while
the sample temperature is
changed at a constant rate. More popular, more stable
baseline.
 The sample and reference are enclosed
in the same furnace
 The difference in energy required to maintain
them at a nearly identical temperature is provided
by the heat changes in the sample

16. Power compensating DSC
•Each sample has own
heater.
•Temperature of samples
controlled independently.
• Less power required
with endotherm Sample.
• In this the power needed to maintain the sample
temperature equal to the reference temperature is
measured. It has lower sensitivity but response time is
more and high resolution.

17. Instrumentation:
 Heat is transferred through the discs and up into
the material through pans.
 The differential heat into the two pans is directly
proportional to the difference in the outputs of the
two thermocouple junctions.
 The sample temperature is measured by the
chromel and alumel junction under the sample

19. Reference Material
 Reference should have same physical
properties as sample
 Reference should not have any
transformations during heating
 Commonly used, SiC, Al2O3, empty
crucible

20.  The Heat capacity (Cp) of the system is the quantity of
heat required to raise the temperature of the system by
1°C. Units Joules /°C.
Cp = q/ ΔT
 Heat flux is given by:
ΔH = Cp ΔT
(or)
dH/dt = Cp dT/dt + f(T,t)
 where:
 Cp = specific heat capacity (J/K/mol)
 T = temperature (°C)
 H = Enthalpy (J /mol)
 dH/dt = heat flow (J/min.)
 dT/dt = heating rate (°C/min.)
 f(T,t) = Kinetic response of the sample ( J/mol)
DSC : HEAT CAPACITY MEASUREMENT

21. APPLICATIONS:
 Inorganic materials, salts and complexes has
been measured to study their physical properties,
chemical changes and qualitative thermal
behavior .
 One special use of DSC for physical changes is
the determination of purity.
 Quantitative applications include determination of
heats of fusion, crystallisation of materials.
 Glass transition temperatures and melting points
are useful for qualitative estimation of materials,
although thermal methods alone cannot be used
for identification.

22.  In this DSC profile, exothermic heat flow is
measured versus temperature.

23. Here the endothermic heat flow is measured versus
temperature.

24. Possible Transitions in a DSC Curve

25.  Tg ( glass transition temperature):
 Seen in an amorphous material.
 No latent heat associated with it, and such
transitions are referred to as second order
transitions.
 All amorphous polymers undergo a change from
glassy state to rubbery state and vice versa at
certain temperature.
 Characteristic for each polymer.
 Glassy plastics, Tg > RT
 Rubbery material, Tg < RT
 Ex. Tg for polystyrene= 373K
Tg for polyvinyl alcohol= 358K

26.  Variants of DSC
 Conventional – linear temperature (cooling,
heating)
programme
 Fast scan DSC – very fast scan rates (also linear)
 MTDSC (modulated temperature DSC) –more
complex temperature programmes, particularly
useful in the investigation of glass transitions
(amorphous materials)
 HPDSC (high pressure DSC) – stability of
materials,
oxidation processes

27.  DIFFERENTIAL THERMAL
ANALYSIS (DTA)
 Differential Thermal Analysis (DTA) measures the
temperatures and temperature differences
(between sample and reference) associated with
transitions in materials as a function of time and
temperature in a controlled atmosphere.
 This differential temperature is then plotted against
time, or against temperature (DTA curve
or thermogram).
 Changes in the sample, either exothermic or
endothermic, can be detected relative to the inert
reference.
 A DTA curve provides data on the transformations
that have occurred, such as glass transitions,
crystallization, melting and sublimation.

29.  The temperature difference is finite only when:
1. Heat is evolved or absorbed due to exothermic or
endothermic activity in the sample or
2. Heat capacity of the sample is changing abruptly.
 Temperature difference is directly proportional to
the heat capacity, hence curves resemble specific
heat curves, but are inverted:
 Heat evolution is registered as an upward peak
 Heat absorption as a downward peak

31.  A DTA consists of a sample holder comprising
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.

33.  A DTA curve plots the temperature difference as a function of
temperature (scanning mode) or time (isothermal)

34. DTA : Applications
 In the study of polymeric materials:
1. Physical changes and thermal
transitions
2. Chemical reactions like:
 dehydration,
 degradation and curing, etc.

35. THERMOGRAVIMETRIC
ANALYSIS (TGA)
 Changes in weight with temperature are measured.
 Mostly solid samples are used.
 Ideal sample: small, powdered and evenly spread
in crucible (usually platinum pan).
 The sample is kept in definite environment and
changes in temperature are tuned to
preprogrammed rate.
 Initial sample range: 7-8 to 10-11mg.

36. General considerations
 Suitable samples for TG are solids that undergo
one of the two general types of reaction:
 Processes occuring without change in mass (e.g.,
the melting of a sample) obviously cannot be
studied by TG.
Reactant(s)  Product(s)+Gas (a mass
loss)
Gas+Reactant(s)  Product(s) (a mass
gain)

37. Instrumentation

38. 1. The electro balance and its controller
2. The furnace and temperature sensor
3. The programmer or a computer
4. Data acquisition device/ recorder/ plotter
 A sensitive vacuum reading balance with sensitivity
of 0.1 μm is used to follow the weight change.
 Sample weight is recorded under pressure of 10-4
mm to 1 atm.
 Now a days, coupled with IR or MS to measure
chemical nature of the evolved gases being lost
from sample.
Instrumentation

39. • The sample is placed in a small electrically heated oven
with a thermocouple to accurately measure the
temperature.
• The atmosphere may be purged with an inert gas to
prevent oxidation or other undesired reactions.

40.  The environment of furnace can be changed as
desired.
Ex. Air, nitrogen, inert atmosphere of Ar, etc. with use
of gas inlet and outlet chutes.
 Dynamic and static modes can be applied.
 Results represented as TG curves, variation of the
apparent mass of sample Vs. temperature is
plotted.
 Mass generally represented as: mass loss
𝑊𝑜 − 𝑊𝑡
Where, Wo = initial mass
Wt = mass at a given temperature
 Typical plots are usually of one/two/three or even
multi-step uturned S type of curves.

41.  In order to ascertain steps in TGA traces, the
derivative thermogravimetric (DTG) curves are
frequently constructed.
 DTG curve is represented by:
Rate of mass change per pre-selected
temperature interval, dm/dt Vs. temperature
 DTG curve has well defined peaks superimposing
on rapid fall in the mass loss as observed in TGA
curve.

42. TGA(weight changes) and DSC (heat flow).

43. Ti :
Lowest
temperature at
which the onset of
a mass change can
be detected
Tf :
Lowest temperature
by which the
process responsible
for the mass change
has been completed

44. Thermogravimetric analysis (TGA): Uses
 Typical applications include:
1. Pharmaceutical engineering research & in
industrial quality control.
2. Assessment of thermal stability.
3. Assessment of decomposition temperature.
4. Extent of cure in condensation polymers.
5. Composition and some information on sequence
distribution in copolymers.
6. Composition of filled polymers.
7. Used for drug stability studies and the kinetics of
decomposition.

45. Thermomechanical Analysis (TMA)
 Measurement of mechanical response of a polymer
system as temperature is changed.
 These responses include:
1. expansion and extension of materials or
2. changes in viscoelastic properties and heat
distortions, such as shrinking.
 The temperature range used is: -1500C to 7000C.

46. Instrumentation:
1. Probe assembly(generally quartz glass)
2. Furnace
3. Recorder(LVDT)
4. Thermocouple
 The furnace, containing the sample and probe,
controls the temperature.
 Any motion due to expansion, melting, or other
physical change(in test sample) delivers an electric
signal to a recorder.

48. Uses:
 Measurement of:
1. Penetration or heat deflection
2. Torsion modulus
3. Stress-strain behavior
 Mechanical and Viscoelastic properties of hair and
stratum corneum of the skin (Humphries et al.)
 To look at polymer films and coatings used in
pharmaceutical processes.

49. Reference:
 Hatakeyama T., Quinn F.X., Thermal Analysis
Fundamentals and Applications to Polymer
Science,
Second Edition, John Wiley & Sons Ltd. , 1999.
 JOSEPH D. MENCZEL, R. BRUCE PRIME,
THERMAL ANALYSIS OF POLYMERS
Fundamentals and Applications, A JOHN WILEY &
SONS, INC., PUBLICATION ,2009.
 H. K. D. H. Bhadeshia, Differential Scanning
Calorimetry, University of Cambridge, Materials
Science & Metallurgy.

50. RESEARCH PAPER
 Characterization of Cellulose Acetate
Phthalate (CAP)
P. Roxin, Anders Karlsson, Satish K. Singh
Dept. of Pharmaceutical Analytical Chemistry,
Pharmacia and Upjohn AB, S-751 82 Uppsala,
Sweden.
Drug Development and Industrial Pharmacy,
24(1 I), Page .1025-1041 (1998).
www.dekker.com
Copyright 1998 by Marcel Dekker, Inc.

51. ABSTRACT
 Cellulose acetate phthalate (CAP) is a commonly
used enteric coating polymer.
 CAP powder has been studied by various methods
to determine characteristics that have an influence
on its functionality.
 Other characteristics, such as the molecular mass
distribution, have not been reported earlier.
 Fourier transform infrared spectroscopy (FTIR),
nuclear magnetic resonance (NMR), and thermal
analysis have also been performed on fresh
samples, as well as samples stored under various
temperature und humidity conditions

52. INTRODUCTION
 Cellulose acetate phthalate is a commonly used
tablet coating material employed to produce so-
called enteric films, which resist prolonged contact
with the strongly acidic gastric fluid, but soften,
swell, and finally dissolve in the mildly acidic or
neutral intestinal environment.
 In this work, they report an examination of some of
the polymer characteristics, including the effect of
storage. While a number of these characteristics
have been studied earlier, others (such as the
molecular mass distribution) have not been
reported.
 new methods have also been developed to enable
a more rapid examination of these characteristics
than that allowed by the pharmacopoeia methods,
for instance.

53. Materials and Methods
 CAP was obtained from Eastman Chemical
Company
Sr.No. Batch No.
1) 50103
2) 50105
3) 50106
4) 40706
5) 50104

54. Methods
Thermo gravimetric Analysis:
 Mettler TA4000 system using
a TGA5O analyzer.
 Mass of sample : 20mg
 Sample Pan: Al2O3 crucibles.
 heating rate : 5°C/min
 temperature interval : 50°C-600°C.
 Nitrogen atmosphere was used in the
temperature range 50°C-600°C, and
oxygen was used over 500°C.

55. DSC
 CAP powder samples were subject to
differential scanning calorimetry (DSC)
on a Mettler TA4000 system using a
DSC30 analyser. Sample masses of
approximately 10mg were placed in
aluminium pans with crimped lids and
also lids with pinholes. The scanning rate
was 10°C/min over the range 50°C-
300°C. Nitrogen flow rate was 50ml/min.

58. Results and discussion:
 CAP samples were analysed by TGA to obtain separated
vaporization and thermal degradation steps, such that absolute
values of water content, degree of substituents measured in acetic
and phthalic acid, and pyrolysis products were know. A TGA
thermogram is shown in next slide for a fresh CAP sample Batch
no.40706.
 DSC was used to measure the glass transition temperature Tg of
the CAP powders. A typical thermogram is shown in next slide, in
which both water loss and glass transition phenomena are clearly
visible.
Batch No. Tg ("C)
50103 174
50105 173
50106 172
40706 172
50104 172

59. On examining the storage data in Table , it is seen
that only the storage at the most severe conditions (40°C
65.6 mbar 89% RH) seems to have any measurable
effect on this parameter. From the analysis of total acetic
and phthalic content above, we know that, under this storage
condition, CAP loses a large fraction of substituents
in 15 weeks, so we are essentially measuring a different
polymeric material along with free acetic and phthalic
acids serving as plasticizers.

60. Cellulose acetate phthalate powder has been
studied
by various methods. New methods have been
developed to examine free-acid content,
substituent composition, and molecular mass
distribution; FTIR, NMR, and thermal analysis have
also been performed on fresh samples, as well as
samples stored under various temperature and
humidity conditions.
Glass transition temperatures of CAP samples
were
measured. However, this characteristic of the
polymer is
judged not to be as sensitive to the loss of
substituents
Conclusion