1. Characterizing Polymers
Mini-tutorial

2. First step in characterizing a polymer:
Use your senses (take pictures to document)
What color? Does it fluoresce
Transparent or opaque?
Homogeneous in appearance?
Solid or liquid
Tacky or sticky or brittle or tough
Mass – compare with theoretical yield

3. Describe the material below

4. Describe the material below

5. Second, try and dissolve the polymer in different solvents
Water, ethanol, benzene, methylene chloride, tetrahydrofuran, acetonitrile, hexane, acetone, diethyl ether, dimethyl sulfoxide, N-methyl pyrrolidone (NMP)
Leave it at room temp overnight. Look for swelling if not dissolved.
Boil solvent for 4 hours.
If it doesn’t dissolve its probably cross-linked or really crystalline

6. Types of Polymers & solubility
Polyethylene
33%
Vinyls
16%
Polypropylene
15%
PMMA
ABS
Nylon
Polycarbonate
Saturated Polyester
PEEK
Polyurethane
Some are thermosets as well.
PVC
Not Cross-Linked
90% of market
Thermoplastics
Will reform when melted
Epoxy
Melamine Formaldehyde
Phenolic
Polyester (unsaturated)
Polyimide
Some are thermoplastic as well.
Silicone
Urea Formaldehyde
Cross-linked
10% of market
Thermosets/Elastomers
Will not reform
Polymer Family Tree
Will dissolve
Won’t dissolve

7. Third, Structural Characterization of soluble polymers
1H & 13C & 29Si Nuclear Magnetic Resonance and infrared spectroscopy
Molecular weight by gel permeation chromatography
Composition by combustion analyses
X-ray diffraction on film or powder
Viscosity of dilute solutions- shape of polymer

8. X-ray diffraction Semi-crystalline polymer shows diffraction rings
amorphous polymer shows diffuse band

9. Or third, Structural Characterization of insoluble polymers
• Harder to characterize
Solid state 1H & 13C & 29Si Nuclear Magnetic Resonance and infrared spectroscopy
Composition by combustion analyses
X-ray diffraction on film or powder

10. Morphological Characterization of polymers
If opaque or transluscent, SEM and optical microscopy (bifringence)-crystalline or amorphous & more.
Fracture polymer and look at fracture surfaces
Look for phase separation (like immiscible block copolymers)
Look for long range order
Look for pores

11. Thermal characterization of polymers
Thermal gravimetric analyses (TGA) – determines decomposition temperature
Differential scanning calorimetry (DSC)– detects phase changes (melting or glass transition temperatures) or chemical reactions

12. DSC analysis
FIGURE 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. dΔQ/dt = electrical power difference between sample and ref-
erence; ΔT = difference in temperature between sample and reference.

13. Thermal gravimetric analysis

14. Mechanical characterization of polymers
Stress-strain curves:
Young’s modulus (brittleness)
Tensile strength-pull sample appart
Flexural strength- bend until it breaks
Compressive strength-crush sample
Dynamic mechanical analyses (same info as above but with cyclic application of stress or strain.
Generate modulus temperature curves
Fatigue studies to predict failure under cyclic stress

15. Stress-Strain Analysis
Tensile strength = pull sample appart
Chains in neck align along elongation direction: strengthening σ
Elongation by extension of neck ε

16. TIME DEPENDENT DEFORMATION
• Stress relaxation test:
• Data: Large drop in Er
for T > Tg.
(amorphous
polystyrene)
--strain to eo and hold.
--observe decrease in
stress with time.
Adapted from Fig. 15.7, Callister 6e. (Fig is from A.V. Tobolsky, Properties and Structures of Polymers, John Wiley and Sons, Inc., 1960.)
• Relaxation modulus:
• Sample Tg(C) values:
PE (low Mw)
PE (high Mw)
PVC PS PC
-110
- 90
+ 87
+100
+150
Selected values from Table 15.2, Callister 6e. 27

17. Not every polymer needs all of these analyses, but structure is the most basic and important
Known (described in literature) polymers need less structural characterization. Often just IR and Mw from GPC.
New polymers need complete structural characterization: NMR, IR, Combustion analysis, GPC, solubility, glass transition temp and/or melting point.

18. Morphological and Mechanical studies are dependent on research interests.
If you are interested in strong polymers, then morphological, mechanical & thermal studies are important
Other applications requiring morphological, mechanical & thermal studies would include preparation and testing of 1) membranes, 2) coatings, 3) paint, 4) polymer foams, 5) organic photovoltaics, 6) OLED’s, 7) adhesives and 8) low friction coatings

19. Other polymer properties that are important for specialty polymers
Coatings, packaging, membranes, Photovoltaics & OLED’s; gas and water permeability should be measured.
Battery and fuel cell membranes: gas & water permeability and ion conductivity
Dielectrics, wiring insulation: dielectric and electrical conductivity
Fabrics & building materials: fire resistance
Any polymer used in sunlight or radiation or in the presence of chemicals: resistance to oxidative degradation.