Chapter 5. Evaluation, Characterization, and
Analysis of Polymers
5.1 Introduction.
5.2 Chemical Methods of Analysis.
5.3 Spectroscopic Methods of Analysis.
5.4 X-ray, Electro, and Neutron Scattering.
5.5 Characterization and Analysis of Polymer Surfaces.
5.6 Thermal Analysis.
5.7 Measurement of Mechanical Properties.
5.8 Evaluation of Chemical Resistance.
5.9 Evaluation of Electrical Properties.
POLYMER CHEMISTRY
5.1 Introduction.
A. Complexities of polymer characterization.
a. The complexity of molecules: configuration and conformation.
b. The complexity of polymer morphology: crystalline and
amorphous state.
c. Variability of additives: mixture type of materials.
POLYMER CHEMISTRY
5.1 Introduction.
B. Types of polymer characterization.
a. Spectroscopical analysis.
b. Thermal analysis.
c. Surface analysis.
Instrumental method.
d. Mechanical and electrical testing.
e. Chromatographic analysis.
f. Chemical analysis.
early traditional method
by chemical reaction.
POLYMER CHEMISTRY
5.1 Introduction.
C. Standardization for analytical methods.
a. American Society for Testing and Materials (ASTM).
b. British Standards Institute (BSI).
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5.2 Chemical Methods of Analysis.
A. Periodic acid and lead tetraacetate oxidation
a. To determine backbone structure of poly(vinyl alcohol).
Head-to-tail or head-to-head
OH
OH
C
C
HIO4 or Pb(OAc)4
C
O
+ O
C
b. To determine solution viscosity after oxidation of poly(vinyl alcohol).
Decreasing solution viscosity: head-to-head structure.
POLYMER CHEMISTRY
5.2 Chemical Methods of Analysis.
B. Ozonolysis for diene polymer
O
1. O3
H
O
2. H2O
a. To determine the backbone structure of the natural rubber.
b. Degradative product : 4-Ketopentanal.
c. 1-4-cis addition of isoprene.
POLYMER CHEMISTRY
5.3 Spectroscopic Methods of Analysis.
TABLE 5.1. Spectroscopic and Scattering Methods Commonly Used for Studying Polymers
Vibrational
Infrared (IR)
Raman
Spin resonance
Nuclear magnetic resonance (NMR)
(Proton and carbon-13)
Electron spin resonance (ESR)
Electronic
Ultraviolet (UV)-visible
Fluorescence
Scattering
X-ray
Electron
Neutron
Transmittance (%)
Micrometers
Wave number (cm-1)
FIGURE 5.1. Infrared spectrum (KBr pellets) of polyimide (
) and model compound (----).
19
[Reprinted from Troy, Sobanski, and Stevens, by courtesy of Marcel Dekker, Inc.]
5.3 Spectroscopic Methods of Analysis.
5.3.1 Infrared.
A. FTIR spectroscopy.
a. FT: Fourier transform.
Principle of Interferometry.
b. Vibrational transition of chemical bonds.
c. qualitative identification of unknown polymer by using DB.
POLYMER CHEMISTRY
5.3 Spectroscopic Methods of Analysis.
B. Analysis of Morphology.
a. Annealed isotactic polystyrene: semicrystalline.
b. Heating up to Tm and quenching: amorphous.
c. Subtracting amorphous from spectrum crystalline spectrum.
Figure 5.2. Fourier transform-infrared spectra of isotactic
polystyrene in the 640 to 840 cm-1 region: (A) semicrystalline;
(B) amorphous; and (c) the difference spectrum obtained by
subtracting B from A. [From Painter and Koening,21
copyright 1977. Reprinted by permission of John Wiley &
Sons, Inc.]
5.3 Spectroscopic Methods of Analysis.
C. Characterization of blends: Noryls (PS+PPO).
a. Immiscible blends: superposition of two spectra of homopolymers
b. Miscible blends: superposition of three spectra of homopolymers and
interaction spectrum.
c. Interaction spectrum: dipole-dipole coupling of the benzene rings of PS+PPO.
POLYMER CHEMISTRY
5.3 Spectroscopic Methods of Analysis.
5.3.2 Raman
A. Raman spectroscopy.
a. Impinging visible light onto molecular vibrations.
b. To major scattered light depended on the vibration.
c. Symmetric vibration: Raman active (μ=0)
complementary
d. Asymmetric vibration: IR active (μ≠0)
e. Raman light: laser.
POLYMER CHEMISTRY
5.3 Spectroscopic Methods of Analysis.
B. Applications to polymer study.
a. Conformational study of polymer.
b. Cis-trans isomers of elastomer.
c. Sulfur crosslinked polymer.
d. Water solution of polymer.
POLYMER CHEMISTRY
5.3 Spectroscopic Methods of Analysis.
5.3.3 Nuclear Magnetic Resonance.
A. Nuclear Resonance.
a. Detectable nuclei: odd spin quantum number
1H, 13C, 19F, 31P.
b. Resonance energy: radiofrequency.
c. Detectable parameter: chemical shift, coupling constant,
integration, relaxation time.
POLYMER CHEMISTRY
Nuclear magnetic resonance (NMR)
Pacific Northwest National
Laboratory's high magnetic
field (800 MHz, 18.8 T) NMR
900MHz, 21.2 T NMR Magnet spectrometer being loaded
with a sample.
at HWB-NMR, Birmingham,
UK being loaded with a
B. Types of NMR.
a. Solution state NMR.
1) Chemical structure identification by using
1H and 13C environment.
2) Tacticity of polymer.
FIGURE 5.3. 500-MHz 1H nuclear magnetic resonance
spectrum of isotactic poly(methyl methacrylate)
(10% weight/volume solution in chlorobenwene-d5
at 100oC) at three values of gain. E, t: erythro and
threo placement of methylene protons with respect to
ester groups; m, r: meso and racemic dyads.
[Courtesy of Dr. Frank Bovey, Bell Laboratories.
From Schilling, Bovey, Bruch, and Kozlowski, 35
copyright 1985. Reprinted by permission of the
American Chemical Society.]
B. Types of NMR.
b. Solid state NMR.
1) Dipolar interactions and long relaxation times.
2) Anisotropy of the chemical shift in all possible directions.
3) Cross-polarization: effectively speeds up carbon's spin.
4) Magic angle spinning: at 54.7°, rapid spinning.
5) Directly majoring solid sample: Crosslinked and bulk polymers
FIGURE 5.5. Solid-state proton-decoupled 13C nuclear
magnetic resonance spectrum of polycarbonate (A) with and
(B) without cross-polarization magic angle spinning. Peak
assignments: (a) carbonyl carbon; (b) substituted
Ring carbons; and (c) unsubstituted ring carbons. [From
Schaefer, Stejskal, and Buchdahl,38 copyright 1977.
Reprinted by permission lf the American Chemical Society.]
B. Types of NMR.
c. MRI: Magnetic resonance imaging.
1) A technique analogous to medical diagnosis.
2) Quality control for fabricated polymer samples.
3) Characterization of phase boundaries.
4) Monitoring penetration of fluids into polymer.
POLYMER CHEMISTRY
Magnetic resonance imaging (MRI)
A fMRI scan showing regions of activation in orange,
including the primary visual cortex (V1, BA17).
Modern 3 tesla clinical MRI scanner.
Magnetic Resonance Angiography
5.3.4 Electron Spin Resonance (ESR),
Electron paramagnetic resonance (EPR).
A. Principles of ESR.
a. The same principles as NMR.
b. Resonance energy : microwave frequencies.
c. Spin transition of unpaired electron : Radical.
d. ESR spectra: direct absorption curve.
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B. Applications to polymers.
a. Radical reaction (polymerization, degradation and oxidation)
1) Hyperfine splitting: six-line= 4α+1β.
2) Radical surrounded by five protons.
CH2CH
UV
CH2CH
+
Cl
FIGURE 5.6. Electron spin resonance spectrum of UV-irradiated poly(vinyl chloride) at -196oC.
[From Yang, Liutkas, and Haubenstock,40 copyright 1980. Reprinted by permission of the American Chemical Society.]
Cl
B. Applications to polymers.
b. Spin label.
Transition metal or a nitroxide radical containing polymer.
c. Spin probe.
To mix a compound containing an unpaired electron.
Molecular motion and relaxation phenomena.
POLYMER CHEMISTRY
5.3.5 Ultraviolet (UV) - visible
A. Principles of UV-visible.
a. Electronic excitation: n→π* , π→π*
b. Detectable chromophore : conjugated double bond or aromatic
compound.
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5.3.5 Ultraviolet (UV) - visible
B. Application to polymers.
a. Residual monomer, inhibitor, antioxidants contained chromophore.
ex) styrene monomer.
b. Evaluating copolymer composition in case of chromophore
containing monomers.
c. Identifying end groups.
d. molar absorptivity (Beer-Lambert law).
1) Tacticity.
2) Sequence length.
3) Interaction between chromophores and functional group.
4) Solvent.
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5.3.5 Ultraviolet (UV) - visible
C. ORD (Optical rotatory dispersion).
a. Optical rotation as a function of wavelength.
b. Biopolymers, Optical active polymer.
POLYMER CHEMISTRY
5.3.6 Fluorescence
A. Principles of luminescence.
a.
B. Fluorescent spectra.
a. Intensity of the emitted light as
a function of wavelength.
b. Exiplexes:
donor + acceptor (charge transfer complex).
c. Compatibility: donor containing
polymer + acceptor containing polymer.
Energy transfer: miscible
FIGURE 11.1. Energy level diagram and
summary of photochemical processes.
5.4 X-ray, Electro, and Neutron Scattering
A. X-ray scattering.
a. X-ray source:
b. Two types of X-ray scattering.
1) WAXS (coherently): no change wavelength or phase.
2) SAXS (incoherently): change in both wavelength and phase.
c. Information from the X-ray scattering.
1) Degree of crystallinity.
2) Dimension of crystalline domains.
3) Bond distances and angles.
4) Type of conformation in the crystalline regions.
POLYMER CHEMISTRY
FICURE 5.7. Wide-angle and small-angle x-ray diffraction techniques. [From E. A. Collins, J. Bares,
and F. Billmeyer, Experiments in Polymer Science. Wiley-Interscience, copyright 1973. Reprinted by
permission of John Wiley & Sons, Inc.]
5.4 X-ray, Electro, and Neutron Scattering
B. Electron scattering.
a. Electron source : Cathode-ray tube.
b. Transmission electron microscope (TEM)
Resolution : 2 ~ 5Å (×200,000 to 500,000)
c. Informations from the electron scattering.
1) Crystal dimensions.
2) Degree of crystallinity.
POLYMER CHEMISTRY
5.4 X-ray, Electro, and Neutron Scattering
B. Electron scattering.
d. Advantage.
1) Both diffraction and transmission measurements.
2) Small sample size.
3) High diffraction intensity and reflection number.
e. Disadvantage.
1) Causing free radical reaction.
2) Scission of crosslinking.
POLYMER CHEMISTRY
5.4 X-ray, Electro, and Neutron Scattering
C. Neutron scattering.
a. Neutron source : nuclear reactor.
b. Neutron detector : neutron counter.
c. Information from the Neutron scattering.
1) Elastic scattering : the same information as X-ray or TEM.
2) Inelastic scattering
① Hydrogen atom movement.
② Chain folding in lamellae (short-chain).
③ Two states (solid, liquid or solution).
POLYMER CHEMISTRY
5.5 Characterization and Analysis of Polymer Surfaces.
A. Area of surface analysis.
a. In low molecular weight compound.
1) Catalysts.
2) Semiconductors.
3) Other electronics devices.
b. In polymer.
1) Coatings
2) Interface of polymer-catalyst, polymer-filler interfaces.
3) Surface oxidation.
4) Surface morphology.
POLYMER CHEMISTRY
5.5 Characterization and Analysis of Polymer Surfaces.
B. Theory of surface analysis.
Beam
source
Surface of
specimen
Detection
C. Types of surface analysis.
D. Detection pressure : 10-11 - 10-7 torr
POLYMER CHEMISTRY
5.5.1 Scanning Electron Microscopy (SEM)
A. Electron beam.
a. Source : Cathode-ray tube.
b. Fine electron incident beam.
c. To be scanned across the sample surface.
d. Resolution : 100Å.
B. Information from SEM.
a. Topology of surface or surface morphology.
b. Pigment dispersions in paints.
c. Blistering or cracking of coatings.
d. Phase boundaries.
e. Cell structure of polymer foams.
f. Adhesive failures.
POLYMER CHEMISTRY
Scanning Electron Microscopy (SEM)
Transmission Electron Microscopy (TEM)
TEM & SEM
1: Electronen cannon in the upper part of the column.
2 Electro-magnetic lenses to direct and focus the electron beam inside the
column. 3: Vacuum pumps system.
4: Opening to insert a grid with samples into the high-vacuum chamber for
observation. 5: Operation panels (left for alignment; right for magnification and
focussing; arrows for positioning the object inside the chamber). 6: Screen for
menu and image display. 7: Water supply to cool the instrument.
1: Electron gun in the upper part of the column (here a so-called field-emission source).
2 Electro-magnetic lenses to direct and focus the electron beam inside the column.
3: Vacuum pumps system. 4: Opening to insert the object into the high-vacuum observation chamber
in conventional SEM mode.
5: Operation panel with focus, alignment and magnification tools and a joystick for positioning of the sample.
6: Screen for menu and image display. 7: Cryo-unit to prepare (break, coat and sublimate)
frozen material before insertion in
the observation chamber in Cryo-SEM mode. 8: Electronics stored in cupboards under the desk.
9: Technicians Mieke Wolters-Arts and Geert-Jan Janssen discussing a view.
SEM
<그림2.1>동일 생체시료를 관찰한 광학현미경의 이미지(a)와 SEM의 이미지(b)
다중껍질 탄소그라펜 나노구의 TEM 사진
5.5.2 Attenuated Total Reflectance Spectroscopy (ATR)
A. Characteristics of ATR.
a. Light source : IR beam.
b. To be attachable with IR.
c. lower cost.
d. To be attached to crystal (ThBr, AgCl).
POLYMER CHEMISTRY
5.5.2 Attenuated Total Reflectance Spectroscopy (ATR)
B. Principle of ATR.
a. Angle of incident beam : greater than critical angle for reflection.
b.
FIGURE 5.8. Attenuated total reflectance (ATR) : (a) single reflection, and
(b) multiple internal reflection (MIR)
5.5.2 Attenuated Total Reflectance Spectroscopy (ATR)
C. Application
a. Surface coating.
b. Surface oxidation.
c. Adhesive substrate interfaces.
d. Other aspects of polymer surfaces.
POLYMER CHEMISTRY
5.5.3 Photoacoustic Spectroscopy (PAS)
A.
a. Light source : IR, UV-visible.
b. Signal is very low.
c. Scanning : several thousand times.
B. Usefulness of PAS
a. Air-or moisture sensitive
polymer.
b. To detect subsurface by
change of modulation.
FIGURE 5.9. Schematic of the photoacoustic process.
POLYMER CHEMISTRY
5.5.4 Electron Spectroscopy for Chemical Analysis
(or Applications) (ESCA) and Auger Electron Spectroscopy (AES)
A. ESCA
EB = hv - Ekin
EB : Binding energy
hv : Incident X-ray
Ekin : The kinetic energy of the emitted electron
POLYMER CHEMISTRY
FIGURE 5.10. Schematic diagram of an electron spectroscopy for chemical analysis (ESCA) spectrometer. [From Rabek,67 copyright 1980. Reprinted by permission of John Wiley & Sons, Ltd.]
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FIGURE 5.11. Electron spectroscopy for chemical analysis (ESCA) spectra of films: (A) Polystyrene and poly(ethylene oxide); and (B),
(c) Polystyrne-block-poly(ethylene oxide) cast from chloroform and ethylbenzene, respectively.[From Thomas and O’Malley,69 copyRight 1979. Reprinted by permission of the American Chemical Society.]
POLYMER CHEMISTRY
5.5.4 Electron Spectroscopy for Chemical Analysis
(or Applications) (ESCA) and Auger Electron Spectroscopy (AES)
B. AES
a. Auger electron : 2s, 2p electrons → 1s and 2s.
EB = Ekin(1s) + EB(2s) + EB(2p)
b. Application : Polymer-metal interface characterization.
c. Complements of ESCA.
POLYMER CHEMISTRY
5.5.5 Secondary-Ion Mass Spectrometry (SIMS)
and Ion-Scattering Spectroscopy (ISS)
A. Principle
a. Inert gas ion (Primary ion) irradiation.
b. Surface sputtering : ejection of atomic and molecular fragmentation.
B. The method of Ion-scattering.
FIGURE 5.12. Representation of surface sputtering and primary ion elastic scattering as the basis of
Secondary-ion mass spectrometry (SIMS) and ion-scattering spectroscopy (ISS), respectively.
5.5.5 Secondary-Ion Mass Spectrometry (SIMS)
and Ion-Scattering Spectroscopy (ISS)
C. Example of spectra.
FIGURE 5.13. Secondary-ion mass
spectrometry-positive ion spectrum
of polytetrafluoroethylene showing
surface contamination. (20Ne used
as the sputtering gas.) [From Hercules and Hercules,71reprinted with
Permission.]
POLYMER CHEMISTRY
5.5.6 Atomic Force Microscopy (AFM)
A. Schematic diagram of an AFM
FIGURE 5.14. Schematic diagram of an atomic force microscope.
5.6 Thermal Analysis
5.6.1 Differential Scanning Calorimetry (DSC)
and Differential Thermal Analysis (DTA)
A. Schematic diagram
FIGURE 5.15. Schematic representations of differential
thermal analysis (DTA) and differential scanning calorimetry (DSC) measuring cells. [From Rabek,76 copyright
1980. Reprinted by permission of John Wiley & Sons,
Ltd.]
B.
FIGURE 5.16. Idealized differential scanning calorimetry (DSC) or differential thermal analysis (DTA)
thermogram: (A) temperature of glass transition, Tg; (B) crystallization; (C) crystalline melting point, Tm;
(D) crosslinking; and (E) vaporization. dQ/dt = electrical power difference between sample and reference; T = difference in temperature between sample and reference.
POLYMER CHEMISTRY
FIGURE 5.17. Differential thermal analysis (DTA) thermogram
of poly(vinyl chloride): (A) glass
transition, Tg; (B) melting point;
(c) oxidative attack; (D) dehydrochlorination; and (E) probable
depolymerization. [From Matlack
and Metzger,79 copyright 1966.
reprinted by permission of John
wiley & Sons, Inc.]
POLYMER CHEMISTRY
1
2
1
2
Baseline
B
A
Tg
A
B
Tm
FIGURE 5.18. Methods of reporting transition temperatures: (A) at the onset, and (B) at the inflection
point or maximum, Tg= glass transition temperature; Tm= crystalline melting point.
5.6.2 Thermomechanical Analysis (TMA)
A. The method of TMA
a. Using the probe sensing volume and modulus.
b. Measuring volume change and modulus change during heating.
c. Volume change : flat probe tip.
Modulus change : tapered tip.
d. Determining movement of the probe by variable transformer.
e. TMA is more sensitive than DSC and DTA.
B. Torsional braid analysis (TBA).
a. Glass braid or thread is impregnated with the polymer sample.
b. Determining torsional oscillation of braid and thread.
POLYMER CHEMISTRY
5.6.3 Thermogravimetric Analysis (TGA).
A. TGA : Determining thermal stability of polymer.
a. Determining weight loss as sample temperature is increased.
b. Measuring weight loss by thermobalance.
c. Determination environment : in air or in N2.
B. Thermogram
5.6.3 Thermogravimetric Analysis (TGA).
C. Application
a. Information of thermal stability : initial weight loss temperature,
10% weight loss temperature, 50% weight loss temperature.
b. Polymer reactions by heating.
1) HCl from poly(vinyl chloride).
2) H2O from amic acid to make polyimide.
D. Isothermal TGA :
weight loss with time at a constant temperature.
POLYMER CHEMISTRY
5.6.4 Pyrolysis-gas chromatography (PGC)
A. PGC : Pyrolysis device + GC column.
B. Types of pyrolysis device.
a. Furnace chamber pyrolysis : in the heated chamber.
b. Flash pyrolysis : high-resistance coil or filament coated
by polymer sample.
c. laser pyrolysis : focused laser beam.
C. Pyrogram.
FIGURE 5.20. Pyrogram of high-density polyethylene. Peaks correspond to (1) n-alkane, (2) 1-alkene,
and (3) ,-alkadiene. Conditions: 25-m capillary column coated with poly(phenyl ether); pyrolysis
10 s at 1,000oC. [From Kolb et al.,89 courtesy of Springer-Verlag.]
5.6.5 Flammability Testing
A. Limiting oxygen index (LOI).
a. The most versatile small-scale test.
b. Minimum percentage of oxygen for burning.
c. Burning condition : candlelike burning in three minutes.
d.
LOI =
vol. O2
vol. O2 + vol. N2
 100
POLYMER CHEMISTRY
5.6.5 Flammability Testing
B. LOI test
FIGURE 5.21. Schematic representation of the limiting oxygen index (LOI) test
[Adapted from Fenimore and Martin.93]
POLYMER CHEMISTRY
POLYMER CHEMISTRY
5.7 Measurement of Mechanical Properties.
A. Tensile strength, moldulus, elongation measurement.
a. Size of specimen.
b. Instrument : Instron
1) Loads weight range : few grams ~ 20,000 founds.
2) Measuring compressive and flexural strengths.
3) To obtain stress-strain curve by this instrument.
c. Fatigue
1) Alternative cycles of tensile and compressive stress.
2) Fatigue resistance decreases as polymer rigidity or crosslinking increases
POLYMER CHEMISTRY
a. Size of specimen.
b. Instrument : Instron
B. Impact strength.
a. Izod test : Striking weighted pendulum.
b. Specimen size
C. Hardness.
a. Resistance to surface indentation.
b. Indenting device : Spring-loaded needle-type indenter.
D. Abrasion resistance.
a. To measure weight loss by abrader or finely divided abrasive.
E. Tear resistance.
a. A weighted pendulum-mounted blade.
b. Travel distance of pendulum.
POLYMER CHEMISTRY
5.8 Evaluation of Chemical Resistance.
A. Resistance of chemical reagent.
a. Immersing test samples in the chemical reagent
(temperature and time).
b. Measuring mechanical property change after immersing.
c. Measuring retention of properties.
d. Checking swelling, surface erosion, or crazing.
e. Determining change in viscosity.
POLYMER CHEMISTRY
5.8 Evaluation of Chemical Resistance.
B. Moisture resistance.
a. Long-term exposure to water.
C. Weatherability.
a. Weathering chamber.
1) Humidity control.
2) Water spray.
3) UV lamps.
POLYMER CHEMISTRY
5.9 Evaluation of Electrical Properties.
A. Resistivity measurement.
a. Volume resistivity (ρv).
Rv A
E A
=
Iv t
t
E : the potential in volts.
Iv : the measured dc current in amps.
A : the area of the small electrode in square centimeters.
t : the thickness in centimeters.
v =
b. Surface resistivity(ρs).
v =
R D
E Dm
= s gm
Is g
I v: the current (amp).
Dm : the mean diameter of the gap (cm).
g : the width of the gap (cm).
Rs : the resistance (ohm).
POLYMER CHEMISTRY
5.9 Evaluation of Electrical Properties.
c. Unit of resistivity : ohm cm.
1) Insulator : above 108ohm cm
2) Semiconductor : 10-3 - 108 ohm cm
3) Conductor : below 10-3 ohm cm
d. Instrument
POLYMER CHEMISTRY
5.9 Evaluation of Electrical Properties.
B. Dielectric strength :
Maximum voltage which sample can withstand.
C. Dielectric constant :
a measure of a samples contribution to the circuit capacitance.
D. Arc resistance :
the length of time before a high-voltage discharge arc
POLYMER CHEMISTRY