1. EBB245 Materials Characterization
Assoc. Prof. Ir. Dr. Cheong Kuan Yew
School of Materials & Mineral Resources Engineering
Engineering Campus
Universiti Sains Malaysia

2. Synopsis
This course will discuss material characterization techniques from the theoretical aspect, instrumentation and application.

3. Outcome After completion of this course, audience will be able:
To comprehend concept of materials characterization including theory, working principle and application.
To select and apply suitable technique(s) for properties’ characterization of materials in any applications.
To analyze the characterization results qualitatively and quantitatively.
To understand the importance of materials characterization for materials engineers

4. Outline Thermal Analysis Visible and UV Spectrometry
Fourier Transform Infrared Spectrometry
Atomic Absorption Spectrometry

5. Reference
S. Zhang, L. Li, and A. Kumar, “Materials Characterization Technqiues,” CRC Press, 2009.
Y. Leng, “Materials Characterization: Introduction to Microscopic and Spectroscopic Methods, “Wiley, Singapore, 2010.
E.N. Kaufmann (Ed), “Characterization of Materials,”Wiley, New Jersey, 2003.
M. Reading and P.J. Haines; “Thermomechanical, dynamic mechanical and associated methods” in; P. J. Haines; “Thermal methods of analysis: Principles, Applications and Problems” Blackie, London (1995) pp
K.P. Menard; “Dynamic Mechanical Analysis: A Practical Introduction to Techniques and Applications”, CRC Press, Boca Raton (1999)
D. M. Price, “Thermomechanical and Thermoelectrical Methods”, in P.J. Haines (ed.) Principles of Thermal Analysis & Calorimetry, ch. 4, Royal Society of Chemistry, Cambridge (2002) pp

6. Thermal Analysis

7. Physical Property
Derived Techniques
Mass
TG, thermoparticulate analysis, evolved gas analysis
Temperature
DTA
Enthalpy
DSC
Dimension
Thermodilatomery
Mechanical characteristic
DMA
Acoustic characteristic
Thermosonimetry
Optical characteristic
Thermoptometry
Electrical characteristic
Thermoelectrometry
Magnetic characteristic
Thermomagnetometry
Thermal diffusivity & Thermal conductivity

8. Introduction
Methods of measuring properties of materials change as a function of temperature (thermal event).
Properties change: dimension, mass, phase, mechanical behaviour.
Technique
Abbreviation
Measurement
Thermogravimetry TG
Mass change
Differential thermal analysis
DTA
Temperature difference
Differential scanning calorimetry
DSC
Heat flow
Dilatometry -
Length or volume change
Thermomechanical analysis
TMA
Deformation
Dynamic mechanical analysis
DMA

9. Thermal events during heating of a solid in an inert atmosphere (constant pressure)
Reaction
Heat Flow (H) 3
Mass Change in Solid
Solid phase transformation 1
A (solid )  A (solid )
+ or - no
Glass transition 2
A (glass)  A (rubber)
Melting
A (solid)  A (liquid) +
Sublimation
A (solid)  A (gas)
yes
Thermal decomposition
A (solid)  B (solid) + C (gas)
1: first-order phase transition
2: second-order phase transition
3: H = enthalpy change

10. Enthalpy Change Constant pressure 1st Law of Thermodynamics
Heat: energy transfer between a system and its surrounding due to temperature differences.
Work: all types of energy transfer other than heat.
Internal energy change of a system
Heat flow into a system
Work done by the system

11. Constant pressure & mechanical work of volume change in a system.
Enthalpy change (H)

12. Instrumentation Furnace (heating or cooling) Controllable environment
Transducer (monitoring properties change)
Temperature profile
Constant heating rate
Modulated or dynamic heating rate
Isothermal
Display (thermal analysis curve)
Peaks
Discontinuities
Slope change

13. Experimental Parameters
Sample dimension
Sample mass (<10 mg)
Heating (cooling) rate
Atmosphere
Thermal and mechanical history of sample
What is the effect of instrumental and experimental parameters are not identical ?
Impossible to obtain reproducible chemical species

14. Thermogravimetric Analysis (TGA)
Measures change in mass (m) of sample as a function of temperature or time (isothermal).
Application:
Decomposition of material
Thermal stability of material
Degradation temperature of polymeric material
Residual solvent level
Absorbed moisture content
Amount of inorganic (noncombustible) filler in polymer or composite material compositions
Determination of evaporation rate, water content and Curie temperature of magnetic material

15. Ti
Mass Change (%) Tj
Reaction Interval
-100
Temperature (K)

16. Instrumentation Microbalance (thermobalance) Furnace
Temperature programmer
Computer
Microbalance
Computer
Furnace with sample in crucible
Temperature Programmer

18. Schematic thermobalance: sample heated at certain rate in a controlled atm. Solid samples 1 mg to 100 mg but sometimes up to 100 g.

19. Sample is placed into a tared TGA sample pan, which is attached to a sensitive microbalance assembly.
Sample holder is then placed into high temperature furnace.
Balance assembly weigh the initial sample at room T & then continuously monitors changes in sample weight (losses or gains) as heat is applied to sample.
Heat applied at certain rate, in various environment. Typical environment:
ambient air, vacuum, inert gas, oxidizing/reducing gases, corrosive gases, carburizing gases, vapors of liquids or "self-generating atmosphere".
pressure can range from high vacuum or controlled vacuum, through ambient, to elevated and high pressure; the latter is hardly practical due to strong disturbances.

20. Temperature Calibration Heating Rate
Experimental Aspects
Sample
Atmosphere
Temperature Calibration
Heating Rate
Sample holder (geometry, size, heat sink properties)

21. Sample
Mass
Small sample mass (resolution  microbalance)
Volume
Form

22. Atmosphere Reactive (corrosive, oxidizing, reducing gases)
Non-reactive atmosphere (dry Ar, dry N2, inert gas with little water vapor)
Flow rate: 15 – 25 ml/min (for 2 – 10 mg)
Gas flow (thermal shielding, buoyancy effect)

23. Buoyancy effects of upward protective gas

25. Temperature calibration
Thermocouple is not touching the sample and sample holder
Difficult to perform temperature calibration
Method to calibrate
Curie point method
Curie point – transition temperature of ferromagnetic materials where they lose ferromagnetism.
Fusible line method
A fusible wire with known melting temperature connects the microbalance suspension wire and inert mass pieces. Melting of the wire causes mass loss.

27. Heating rate

28. Interpretation Seven classification of TG curves
No decomposition with loss of volatile products.
Rapid initial mass loss characteristic of desorption or drying.
decomposition in single stage.
multi-stage decomposition.
multi-stage decomposition but no stable intermediates.
Gain in mass as a result of sample reaction.
reaction product decompose again.

30. Response Weight gain Weight loss
adsorption (physical), oxidation (chemical).
Weight loss
vaporization (physical), desorption (physical), oxidation (physical), decomposition (chemical), dehydration & desolvation (chemical).

31. Depending on polymer composition, reaction upon heating will give their own characteristic TG curve.
Result can give thermal stability of material – desorption, decomposition & oxidation information.

32. Calcium oxalate monohydrate: 3 distinct weight losses.
CaC2O4.H2O  CaC2O4  CaCO3  CaO

34. Molded underfill material (flip chip application): 3 degradation stages. Moisture & volatiles in resin, weakly bonded monomers, then breakage of cross-linked monomers.

35. Multiple-stage reaction: dehydration reaction of hydroxide from LiOH
Multiple-stage reaction: dehydration reaction of hydroxide from LiOH.H2O (exo).
4LiOH.H2O (solid) + O2  2Li2O + 4H2O
Then formation reaction of Li2SnO3 due to reaction between Li2O with SnO2 in mixture (exo).

36. The sample was heated from room temperature to 900°C at a rate of 5°C/min in air.
Polyester (71% of the polymer),
Polystyrene (29% of the polymer),
Fiberglass (22.9% of the whole) and CaCO3 (49.3% of the whole) were easily identified by their different temperatures of combustion or evaporation.
The combustion of the styrene polymer component produced enough energy that the temperature momentarily increased more than the programmed rate.
Thermogravimetric analysis was used as one of several complementary techniques in the identification of an unknown polymer composite.
TGA was then performed on the material to find the weight percent of each material.

41. Slope change in a TG curve
Uncertainty of the slope change
Derivative TG curve (DTG) (dm/dT vs T)
Peak: max of mass change

43. Differential Thermal Analysis (DTA)
To examine thermal events in a sample by heating or cooling without mass exchange with its surroundings.
Application:
Solid phase transformation
Glass transition
Crystallization
Melting
Record temperature difference between sample & reference material.

44. Both solid sample & reference material usually powdered form.
thermally stable at a certain temperature range
Not react with sample holder or thermocouple
both thermal conductivity
heat capacity should be similar to those of sample
Both solid sample & reference material usually powdered form.
Endothermic (T = -ve):
absorbs energy in the form of heat.
Greek prefix endo- = “inside” and the Greek suffix –thermic = “to heat”.
E.g. melting of ice
Exothermic (T = +ve):
releases energy in the form of heat.

45. Butter & margarine

47. TG/DTA scan of montmorillonite clay
Large endothermic at 114°C is assigned to loss of interlayer absorbed water.
2nd endothermic at 704°C is dehydroxylation reaction of the mineral.
Last 2 peaks are attributed to structural changes, since no weight loss are evident in TG.
TG/DTA scan of montmorillonite clay

49. Differential Scanning Calorimetry (DSC)
Measure the heat flow [W/g] difference between sample and reference.
Amount of energy absorbed (endothermic) or released (exothermic) by a material is measured.
DSC system
At constant heating rate () [sample temperature (T) changes with time, t]: Conventional DSC
(1) Heat flux DSC (quantitative DTA – measure temperature difference directly and converts it to heat flow difference)
(2) Power-compensated DSC (directly measure enthalpy change)
Temperature modulated (heating rate is modulated by superimposing a cyclic heating rate on the constant rate): Temperature-Modulated DSC (TMDSC)

52. Sinusoidal temperature modulation
B = amplitude of temperature modulation (1 - 10 K)
 = 1/2p
p = modulation period (10 – 100 s)

53. Advantages of TMDSC over conventional DSC:
Able to separate reversing and non-reversing thermal events.
How to do it?
TMDSC data needs to be deconvoluted to generate standard DSC curves.
DSC curve
dH/dt per mass unit vs. temperature
Total enthalpy change (H) should be proportional to peak area (Ap)
Calibration factor

55. Reversing thermal events
Glass transition and Fusion (melting)
Non-reversing thermal event
Oxidation
Curing
Relaxation
Cold crystallization (glass – crystal transition below melting point)

56. Standard sample for calibration
Well characterized melting temperature and enthalpy changes of melting (latent heat)

57. Physical changes : Chemical changes : DSC Responses
Exothermic – adsorption, crystallization.
Endothermic – desorption, melting, vaporization.
Chemical changes :
Exothermic – oxidation, decomposition, curing.
Endothermic – reduction, decomposition, dehydration.

58. Experimental Aspects Sample requirements Baseline determination
Dense powder or small discs.
Low mass sample.
Crucible (material)
Sealing of pans / crucible (avoid change in mass)
Baseline determination
Instrument (zero) baseline
Contamination
Gas flow rate
Sample baseline
Scanning rate
Thermal history
Heating rate
Atmosphere

59. Transition Peak Temperature
Sample Size
Sensitivity
Resolution
Transition Peak Temperature
Increase
Decrease

60. Heating Rate (deg/min)
Sensitivity
Resolution
Reproducibility
Experimental Time 5
Poor
Very good
Long 20
(recommended)
Good
Intermediate 40
Short

61. Application Transition temperature (DTA & DSC) Enthalpy change (DSC)
Melting
Crystallization
Glass transition
Enthalpy change (DSC)
Heat capacity
Phase transformation and phase diagram
Crystallinity
Compositional analysis / Individual polymer in a polymer mixture
Thermal stability

62. DSC curve for a typical polymer.
Tg – change in heat capacity but no change in enthalpy, ∆H = 0.
DSC directly measures ∆H of transitions. Also degree of crystallinity, degree of curing.

63. Heat is being absorbed by sample (increase in its heat capacity)
Heat is being absorbed by sample (increase in its heat capacity). Polymers gone thru Tg, but transition occur over a temperature range. So Tg is taken as middle of the incline.

64. Crystallization point – Tc where at this temperature polymer have enough energy to arrange into ordered arrangements, crystal. Polymers give off heat at this point. Area of peak = latent energy of crystallization.
Heat absorbed in order to melt – additional heat to increase temperature. Area of dip = heat of melting.

69. Enthalpy Change

70. Scanning Rate

71. Heat capacity (Cp) at constant pressure
Displacement between baseline and sample lines (h) is proportional to sample heat capacity
Calibration factor

73. Phase transformation

74. Phase diagram

75. Thermosetting Polymer
Curing process: exothermic (release heat)
Completion of curing. Shows lass transition temperature

76. Crystallinty of polymeric material
HU = fusion enthalpy (latent heat of melting)
From literatures

77. % of crystallinity calculated relative to 100% crystal material’s Tm peak.

78. Higher crystallinity gives larger & higher Tm peak.

79. Individual polymer in a polymer mixture

80. Thermal stability

81. Case Study

82. Polymer blend – immiscible blend
Polymer blend – immiscible blend. If fully soluble, Tm peak will be in between Tm each elements.

83. Different grades gives different Tg, and thus, different processing temperature.

84. Effect of thermal history on thermoplastic polyester

85. Amorphous metal alloy

86. Underfill material – uncured sample
Underfill material – cured sample

88. DTA
(temp change)
DSC
(heat flow)
Qualitative 
Quantitative
Temperature range
Wider
Narrower
Sample
Higher melting point
Lower melting point
Crucible
Pt or Au Al

89. THERMO-MECHANICAL ANALYSIS (TMA)
Dimensional properties of a sample are measured as sample is heated, cooled or held under isothermal conditions when static or dynamic loading or force being applied.
TMA measurements record changes caused by changes in free volume of a material.
Changes in free volume – by absorption or release of heat associated with that change, loss of stiffness, increase flow, change in relaxation time.
Free volume related to viscoelasticity, aging, penetration by solvents, & impact properties.

90. As the space between the chains increases, the chain can move.
Physical aging Tg
Increase in free volume caused by increased energy absorbed in chains and this increased free volume permits various types of chain movement to occur. Below Tg various paths with different free volume exist depending on heat history & processing of polymer, where the path with the least free volume is most relaxed.

91. Application :
Coefficient of thermal expansion (CTE ) of material.
Tg & Tm of material.
Heat deflection temperature (HDT) of material.
Delamination temperature of composite.
All types of solid – powders, films, fibers, molded pieces, etc.
Use of probe resting on sample under a positive load. As sample is heated, cooled or held isothermally, dimensional changes in sample is translated into linear displacement of probe.

92. Tg in polymer corresponds to the expansion of free volume allowing greater chain mobility above this transition.

93. Coefficient of Thermal Expansion (CTE)
Many materials are used in contact with dissimilar material. Rate & amount of expansion need to be known to help design around mismatches that can cause failure of final product.
Linear CTE (physical CTE)
fractional change in a length of body when heated or cooled through a given temperature range
usually it is given as a coefficient per unit temperature interval, either as an average over a stated range or as tangent to the curve at a given temperature.
α is the instantaneous CTE,
Lo is the original length of the specimen
L is the sample length at temperature T

94. Rearrange equation regarding to y=mx+cα
dl/Lo
From this equation, dT
Linear graph

95. Unidirectional Composite
Longitudinal thermal expansion coefficient, α1:
Transverse thermal expansion coefficient, α2:
Where:

96. Case Study for this polymeric material? A = 4.828µ / °C (59,2.6)1 2 3 10 20 30 40 50 60 70
Temperature o C
Strain, % (10-4)
(59,2.6)
(30,1.2)
Find the Coefficient of Thermal Expansion (CTE)
for this polymeric material?

97. Case Study
A 10 mm length of polymeric material was heated from room temperature 25°C until Tg at 120°C. The CTE of the material was given as 0.65µ /°C. What is the change in length of this material?
A = x 10-3 mm

98. Instrumentation
Expansion probe

99. TMA technique offers several probes:
expansion
penetration
compression
flexure
extension
dilatometry
notes: The most commonly used TMA probe is the expansion probe. This probe rests on
the surface of the test specimen under low loading conditions. As the sample
expands, during heating, the probe is pushed up and the resulting expansion of
the sample is measured.

100. TMA Probes a b c d a: Expansion probe b: Penetration probe
c: Compression probe
d: Flexure probe

101. TMA : (a) penetration & (b) extension.
LVDT – linear variable differential transformer. Also use other types of transducer – laser, optoelectronic.

102. TMA : (c) flexure & (d) torsional measurement.
Dimensional changes are monitored and transducer transform responses into electrical signal (output).

103. Application
Measurement of Tg of epoxy PCB – probe rest on surface under low load. As sample expands during heating, probe is pushed up & resulting expansion of sample is measured.
At Tg, epoxy matrix exhibits significant change in slope due to an increase in its rate of expansion.
Onset T of this expansion = Tg.

104. CTE measurement – quantitative assessment of expansion over a T interval. CTE before Tg = 50.5 µm/m°C, while above Tg, CTE increases to µm/m°C. Also shows residual thermal stress – 1st heat result show undulation in region near Tg  reflects release of stresses.

105. TMA penetration probe – during measurement, loading is added so probe moves down thru sample as it softens. Useful for measuring Tg of coatings on substrate. TMA of wire sample with 2 coatings – inner coating prevents electrical contact between adjacent wires and outer coating used to bond the coil.

106. TMA penetration results on crosslinked and non-crosslinked polyethylenes. Crosslinked sample exhibits smaller degree of penetration due to higher viscosity in liquid region above Tm.
High sensitivity of TMA tech allows it to detect weak transitions otherwise may not be observed by DSC.

107. Extensive crystalline transition, & softening point, Tg.

108. Another sample shows significantly smaller crystalline to amorphous transition dimension increase compared to 1st sample.

109. Limitation:
only for solid samples.
creep occurring concurrently with normal dimensional changes.
usage of proper probe.

110. Thermodilatometry
Dimensional changes over wider temperature range, up to 2000°C in various atmosphere (inert, vacuum, air, etc)

111. Sintering behavior of kaolin & kaolinitic clays – on heating loses water & form metakaolin structure. Then converts to spinel structure (above 960°C) & then above 1100°C to mullite.

112. Dynamic Mechanical Analysis (DMA)
Characterize Visco-Elastic properties
Viscous system - work done by system dissipated as heat.
Elastic system – work stored as potential energy.
Polymer  dual manner, e.g. viscous-elastic.
DMA – info on dynamic properties relating to these behaviour.
Gives 2 properties as a function of T :
Elastic modulus, E’ – energy stored (dynamic storage modulus).
Viscous modulus, E’’ – ability to dissipate energy as heat (dynamic loss modulus).
E’ & E’’ of polymers are measured as a function of temperature or time as the polymer is deformed under an oscillatory load (stress) at a controlled (programmed) temperature in specified atmosphere.
Stiffness & its dampening capacity.

113. Let’s bounce a ball

114. Measures dynamic modulus and/or damping of material under oscillatory load as a function of temperature or time at various frequencies.
Samples – fibers, films, molded sheets, powder.
DMA measures amplitude & phase of displacement of sample in response to an applied oscillating force.
Data then used to calculate stiffness & convert to modulus. Damping factor is also calculated.
A T scan at constant frequency can generate a fingerprint of material’s relaxation processes & its Tg.

115. Advantages of DMA over DSC:
Able to measure side-chain and main-chain motion in specific regions of polymer, as well as relaxation.
DMA is more sensitive in detecting Tg especially Tg of minor component.
Limitation:
Cannot measure mechanical properties over full T range, because sample excessively dampens the applied oscillation as it approaches its softening point.

116. Instrumentation
Sample is fixed between 2 parallel arms that are set into oscillation by an electromagnetic driver at an amplitude selected by operator.
DMA module measure changes in visco-elastic properties of materials resulting from changes in T, atm and time.
It then detects changes in the system’s resonant frequency and supplies the electrical energy needed to maintain the preset amplitude.
Frequency of oscillation is a measure of modulus of the material. The amount of electrical energy needed to maintain constant amplitude  damping properties.

117. Mechanical Testing

118. Frequency & strain pre-selected & maintain constant.
An oscillatory strain is applied to sample in bending or tensile deformation modes as a function of T or time.
Frequency & strain pre-selected & maintain constant.

119. DMA – sample is subjected to sinusoidally varying stress of angular frequency.
For viscoelastic material, resulting strain will also be sinusoidal, but will be out of phase with the applied stress owing to energy dissipation as heat, or damping.
 is the phase angle between stress & strain. Damping calculate from h = (v2 – v1)/vr, or measure driving force to maintain constant amplitude.

120. A sinusoidal oscillating stress is applied to a specimen, a corresponding oscillating strain will be produced.
Unless the material is perfectly elastic, the measured strain will lag behind the applied stress by a phase difference (δ).
Ratio of peak stress to peak strain gives the complex modulus (E*), which comprises an in‑phase component or storage modulus (E’) and a 90° out‑of‑phase (quadrate) component or loss modulus (E”).
If, as in the case of DMA, a sinusoidal oscillating stress is applied to a specimen, a corresponding oscillating strain will be produced. Unless the material is perfectly elastic, the measured strain will lag behind the applied stress by a phase difference (δ) shown in here. The ratio of peak stress to peak strain gives the complex modulus (E*) which comprises an in‑phase component or storage modulus (E’) and a 90° out‑of‑phase (quadrature) component or loss modulus (E”).

121. Young’s modulus, E is related to square of resonance frequency, r.
E = c L4  r2 / B2
c – constant, L – sample length between clamps, B – sample thickness &  - sample density.
Damping usually expressed as logarithmic decrement per cycle, i.e amplitude decay by half, log (A1/A2) = log 2 = Damping is then 3.0 dB. Rate of decay is a measure of how much damping is.
DMA output is plots of resonance frequency and of damping as functions of T.

122. The storage modulus, being in‑phase with the applied stress, represents the elastic component of the material’s behaviour, whereas the loss modulus, deriving from the condition at which d /dt is a maximum, corresponds to the viscous nature of the material. The ratio between the loss and storage moduli (E ”/E’) gives the useful quantity known as the mechanical damping factor (tan δ) which is a measure of the amount of deformational energy that is dissipated as heat during each cycle. The relationship between these quantities can be illustrated by means of an Argand diagram, commonly used to visualise complex numbers, which shows that the complex modulus is a vector quantity characterised by magnitude (E*) and angle (δ) as shown in Figure 3. E’ and E” represent the real and imaginary components of this vector thus:
E* = E’ + iE" = (E'2 + E"2) (8)
So that:
E’ = E* cos δ (9)
and
E" = E* sin δ

123. Test Configurations

124. 3 parameters are calculated:
dynamic storage modulus, E’,
dynamic loss modulus, E’’,
dissipation or damping factor, tan  = E’’/E’.

126. Application

127. DMA result of FRP sample – resonant frequency vs T
DMA result of FRP sample – resonant frequency vs T. storage modulus is proportional to resonant frequency. As T increased, resonant frequency decreased. On-set T taken as Tg.

128. Polycaprolactone

129. Typical behaviour For purely crystalline materials, Tg occurs
Rubbery plateau is related to Me between cross-links or entanglements
Tll in some amorphous polymers
Tm = melting (1)
For thermosets, no Tm occurs
Rubbery plateau (2)
In semicrystalline polymers,
a crystal-crystal slip, Ta* occurs
For purely crystalline materials, Tg occurs
Tg is related to molecular mass up to a limiting value
b transitions are often related to the toughness

130. poly(ester urethane)s
semicrystalline polymers
poly(ester urethane)s
linear amorphous polymers
crosslinked polymers

131. Transition phenomena / mechanical relaxation in HDPE
Transition phenomena / mechanical relaxation in HDPE. Low-T relaxation, γ in polymers is normally associated with improved toughness & impact behavior. α-relaxation is assigned as Tg of polyethylene. α-relaxation requires mobility within crystalline phase & coincides with accelerated softening.

132. DMA of 2 diff samples of PE
DMA of 2 diff samples of PE. (a) 2 peaks : lower T peak attributed to long chain (-CH2-)n relaxation in amorphous region, & higher T peak to similar motion in crystalline phase. T & elative size can be related to degree of crystallinity.
(b) Branched PE show 3 peaks, 1st and 3rd as above, and 2nd peak is attributed to –CH3 relaxation in amorphous phase.

133. Behavior of styrene-butadiene-rubber (SBR)
Behavior of styrene-butadiene-rubber (SBR). Various formulations of SBR – different styrene-butadiene ratios, diff butadiene isomers, diff additives, i.e carbon black affected Tg, modulus of elasticity.
# Changes in Young’s modulus indicate changes in rigidity and hence strength. Damping measurements give practical info on Tg, change in crystallinity, occurrence of cross-linking, & show up features of polymer chains.

134. Case Study

135. Impact Resistance
High- and low-impact nylon samples showing how the b transition is related to sample toughness as measured by impact testing.
The (a) lines show a material with good impact strength by the falling dart test and the (b) line shows one with poor values by the same test.
High- and low-impact nylon samples showing how the b transition is related to sample toughness as measured by impact testing. The (a) lines show a material with good impact strength by the falling dart test and the (b) line shows one with poor values by the same test.

136. Definition of operating range based on position of Tg in epoxy circuit board.

137. Thermoset Cure
The Tg of a chip encapsulation material was measured by DSC and DMA as a function of post cure time.
Tg of a chip encapsulation material was measured by DSC and DMA as a function of post cure time.

138. Methods of determining Tg.
Methods of determining Tg. (a) Multiple methods of determining Tg are shown for DMA. Tg varies by up to 10°C in this example, depending on the value chosen. Differences as great as 25°C have been reported. (b) Four of the different methods used to determine Tg in DSC are shown. The half-height and half-width methods are not included.
Methods of determining Tg.
Multiple methods of determining Tg are shown for DMA. Tg varies by up to 10°C in this example, depending on the value chosen. Differences as great as 25°C have been reported.

139. Effect of Plasticiser
Shear modulus and loss factor (delta tan) for PVC plasticised with diethylphthalate (DEP), dibutyl phthalate (DBP) and n-dioctyl phthalate (DOP).
Shear modulus and loss factor (tan d) for PVC plasticised with diethylphthalate (DEP), dibutyl phthalate (DBP) and n-dioctyl phthalate (DOP).

140. Stress Relief
Stress relief at the Tg in DMA. The overshoot is similar to that seen in DSC and is caused by molecular rearrangements that occur owing to the increased free volume at the transition.
Stress relief at the Tg in DMA. The overshoot is similar to that seen in DSC and is caused by molecular rearrangements that occur owing to the increased free volume at the transition.

141. Cold crystalisation in poly(ethylene terephthalate) caused a large increase in the storage modulus, E', above the Tg. A DSC scan of the same material is included.
Cold crystalisation in poly(ethylene terephthalate) (PET) caused a large increase in the storage modulus, E', above the Tg. A DSC scan of the same material is included.

142. Effect of frequency
DMA results for poly(ethylene terephthalate) film measured in tension at different frequencies shown. The measurements were performed isothermally in 5°C increments and the apparatus allowed to come to thermal equilibrium for 5 minutes before the sequence of measurements was performed.
DMA results for PET film measured in tension at different frequencies shown. The measurements were performed isothermally in 5°C increments and the apparatus allowed to come to thermal equilibrium for 5 min. before the sequence of measurements was performed.

143. Frequency Master Curve
An example of a frequency scan showing the change in a material’s behaviour as the frequency varies. Low frequencies allow the material time to relax and respond, hence flow dominates. High frequencies do not allow relaxation and elastic behaviour dominates.
Frequency Master Curve

144. Effect of Molecular Weight
Molecular weight and flow: the terminal zone or melting region follows the rubbery plateau and is sensitive to the Mw of the polymer.
Molecular weight and flow: the terminal zone or melting region follows the rubbery plateau and is sensitive to the Mw of the polymer.

145. Gellation of Polymer Solution
The crossover point between either E' and E'' or between E' and h* for a material corresponds to the relative molecular weight and molecular weight distribution.
The crossover point between either E' and E'' or between E' and h* for a material corresponds to the relative molecular weight and molecular weight distribution.

146. 1. Determination of tg from tan delta curve 2
1.Determination of tg from tan delta curve 2. determination max peak of tan delta curve
Fig show effect of frequency on the tan delta curve of composites with 40 % fiber loading
Table 1

147. Thermal Diffusivity Measurement Techniques
Transient Heat Flow
Pulse technique
Monotonic heating technique
Periodic Heat Flow
Temperature wave technique
Laser Flash Technique

149. Laser Flash Analysis (LFA)
1961 (Parker et al)
Thermal conductivity ()
Kx = constant related to x percent rise
tx = elapsed time to an x percent rise

150. Instrumentation Laser Detector A to D converter and Amplifier
sample
Laser
Detector
A to D converter and Amplifier
Vacuum or inert atmosphere
Heater
Digital Data Acquisition System
Computer

153. Activity
How to calculate/measure “Thermal Conductivity, ”.