1. Chapter 4. Chemical Structure and Polymer Properties
4.1 Introduction
4.2 Fabrication Methods.
4.3 Mechanical Properties
4.4 Thermal stability
4.5 Flammability and Flame Resistance.
4.6 Chemical Resistance.
4.7 Degradability
4.8 Electrical Conductivity
4.9 Nonlinear Optical Properties
POLYMER CHEMISTRY

2. 4.1 Introduction
A. Relationship between chemical structure and polymer properties.
a. Chemical structure and morphology (Chapter 3).
 b. Polymer properties : mechanical property, thermal property,
    chemical property, electrical property, etc.
B. To tailor chemical structure for specialty polymer.
C. Additives - compounds to modify polymer property.
D. Fabrication method to make polymer articles.
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3. 4.2 Fabrication Methods. A. Molding
a. Compression molding : thermoset polymer.
FIGURE 4.1. Compression molding
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4. b. Injection molding : thermoplastic polymer.
FIGURE 4.2. Injection molding. [Reprinted from V. Hopp and I. Hennig, Handbook of Industrial
Chemistry, copyright 1938, courtesy of McGraw-Hill.]
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5. c. Reaction injection molding (RIM)
FIGURE 4.3. Basic components of a reaction injection molding (RIM) process.
[From Modern Plastics Encyclopedia, Reprinted with permission of Modern Plastics.]
newly developed molding.
   polyurethane and other polymer system.
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6. A. Molding d. Reinforced reaction injection mold (RRIM) :
    Modified RIM for fiber reinforcement.
e. Blow molding : for bottles.
FIGURE 4.4. Blow molding. [Courtesy of the Society of the Plastics, Inc.]
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7. 4.2 Fabrication Methods. B. Casting : for making film.
a. Solution casting and melting casting.
b. Calendering : thick film.
C. Extrusion : to make rods and pipe.
 a. Extruder : screw of injection mold + die instead of mold.
b. sometimes to make thin film by extrusion.
   ex) PE film.
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8. D. Spinning. v a. melt spinning : for molten polymer. b. dry spinning
c. wet spinning : solvent soluble polymer.
Fig.4.5 Basic components for spinning.

9. E. Blowing agent : for foamed plastic.
 a. Physical blowing agent.
  1) Gas : air, nitrogen, carbon dioxide.
  2) Low-boiling liquid : pentane, CFC (not to be used now,
      because of ozone depletion)
 b. Chemical blowing agent.
 1) Byproduct CO2 for polyurethane synthesis.   
2) Decompose on heating and give off nitrogen.
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10. 4.3 Mechanical Properties
A. Molecular weight dependent mechanical properties.
a. For vinyl polymer, molecular weight : 105
    For polyamide, molecular weight : 20,000 ～ 50,000
b. For small molecular weight, properties of end group : significant
    In case of high molecular weight : negligible.
c. Properties and molecular weight.
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11. Property
Molecular weight
Mechanical
Working
range
Nonmechanical
FIGURE 4.6. Dependence of properties on molecular weight
(hypothetical polymer).
Viscosity

12. 4.3 Mechanical Properties
B. Type of mechanical properties.
a. Tensile strength, tensile modulus, elongation.
b. Compressive strength : reverse tensile strength.
c. Flexural strength : Impact resistance, abrasion resistance,
    tear resistance, hardness
POLYMER CHEMISTRY

13. 4.3 Mechanical Properties
C. Tensile strength.
a. Important and useful mechanical property.   
1)  Tensile stress :
2)  Tensile strain :
3)  Tensile modulus :  
b. Units of tensile strength :
 1) CGS : dyne / cm2
   
2) SI : N / m2 (Pa)
3) pounds per square inch (psi)
 = A F
 = l l
E =  
c. Unit of modulus
   same unit of tensile strength.
d. Unit of elongation : No dimension.
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14. Fiber
Brittle
plastic
Stress
()
Elastomer
Strain ()
FIGURE 4.7. Characteristics of tensile stress-strain behavior.

15. FIGURE4.8. General tensile stress-strain curve for a typical thermoplastic.
Elongation at break
Elongation
at yield
Stress
()
Yield
stress
Strain ()
Ultimate
strength

16. D. Temperature dependent mechanical properties
a. The modulus of amorphous thermoplastic depend on temperature.
FIGURE 4.9. Effect of temperature on tensile modulus of an amorphous thermoplastic;
log E, modulus scale; Tg, glass transition temperature.
Glassy
Rubbery
Flow
Temperature
log E
(N/m2) Tg 3 6 9

17.  b. Tensile modulus of crystalline and crosslink polymer depend on temperature.
FIGURE Effect of temperature on tensile modulus (log E scale) of various polymers.
Tm, crystalline melting temperature. [Reprinted with permission from J. J. Aklonis,
J. Chem. Educ., 58, 11 (1981).]
Temperature
log E (N/m2)
Crystalline
Highly
crosslinked
Lightly
Low
molecular
weight
High
weght 3 6 9 Tm

18. > 4.3 Mechnical Properties E. Time dependent mechanical properties
a. viscoelastic property       
b. creep stress relaxation   
>
disentanglement by stress like as temperature
F. General relationship between mechanical property and structure.
a. Flexible backbone : lower tensile property
b. Chain stiffness of backbone or bulky side group :  increase tensile property
c. Chain stiffness : lower impact strength.
     cf) Table 4.1 and Table 4.2
d. Tensile strength of fiber
    Tenacity= N/ tex ,   tex= gram / 1000meters of the fiber.
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19. aValues taken from Aranoff,12a converted to SI units, and rounded off.
TABLE 4.1. Mechanical Properties of Common Homopolymersa
Polymer
Polyethylene,
low density
high density
Polypropylene
Poly(vinyl chloride)
Polystyrene
Poly(methyl
methacrylate)
Polytetra-
fluoroethylene
Nylon 66
Poly(ethylene
terephthalate)
Polycarbonate
Strengthb
(Mpa)
8.3-31
22-31
31-41
41-52
36-52
48-76
14-34
76-83
48-72 66
Modulusb -
2380
Elongation
(%)
40-80
2-10
60-300
50-300
110
Compressive
20-25
38-55
55-90
83-90
72-124 12
103
76-103 86
Flexural
41-55
69-110
69-101
72-131
42-117
96-124 93
Impact
Strengthc
(N/cm)
No break
1.7
9.1
Tensile Properties at Break
Property
aValues taken from Aranoff,12a converted to SI units, and rounded off.
bTo convert megapascals to pounds per square inch, multiply by 145.
cIzod notched impact test (see Chap. 5). To convert newtons per centimeter to foot pounds
per inch, multiply by 1.75.

20. TABLE 4.2. Fiber Propertiesa
Fiber Type
Natural
Cotton
Wool
Synthetic
Polyester
Nylon
Aromatic polyamide
(aramid)c
Polybenzimidazole
Polypropylene
Polyethylene (high strength)
Inorganicc
Glass
Steel
Tenacityb
(N/tex)
0.27
2.65d
0.31
Specific
Gravity
1.50
1.30
1.38
1.14
1.44
1.43
0.90
0.95
2.56
7.7
aUnless otherwise noted, data taken form L. Rebenfeld, in Encyclopedia of Polymer Science and Engineering (H. f. Mark,
N. M. Bikales, C. G. Overberger, G. Menges, and J. I. Kroschwitz, Eds.), Vol. 6, Wiley-Interscience, New York, 1986, pp
bTo convert newtons per tex to grams per denier, multiply by 11.3.
cKevlar (see Chap. 3, structure 58.)
dFrom Chem. Eng. New, 63(8), 7 (1985).
eFrom V. L. Erlich, in Encyclopedia of Polymer Science and Technology (H.F. Mark, N. G. Gaylord, and N. M. Bikales,
Eds.), Vol. 9, Wiley-Interscience, New Uork, 1968, p. 422.

21. 4.4 Thermal stability
A. Chemical structure of thermally stable polymer:
 to have aromatic repeating unit.
TABLE 4.3. Representative Thermally Stable Polymersa
Decomposition
Temperature (oC)b
660
650
640
620
Type
Poly(p-phenylene)
Polybenzimidazole
Polyquinoxaline
Polyoxazole
Structure

22. Decomposition Temperature (oC)b 585c 570 490
TABLE 4.3. Representative Thermally Stable Polymersa
Decomposition
Temperature (oC)b
585c
570
490
Type
Polyimide
Poly(phenylene oxide)
Polythiadiazole
Poly(phenylene sulfide)
Structure
aData from Korshak17
bNitrogen atmosphere unless otherwise indicated.
cHelium atmosphere.
POLYMER CHEMISTRY

23. B. Aromatic or cyclic repeating unit
a. Thermal stability : to bonds cleavage for degradation
b. Poor processability
   1) High Tg or high Tm
   
2) High viscosity of molten polymer   
3) Low solubility
c. Incorporation of inorganic material.
d. Seurcumvent of poor processability
1) Incorporation of flexible chain on backbone or side chain.
2) Insertion of heteroatom.
3) Symmetry→ asymmetry
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24. C. Carl S. Marvel: polybenzimidazole fiber
                                                                                                                                                                                           
a. Astronaut's space suits and firefighters' protective clothing.
b. Cardo polymer (from the Latin cardo, loop)
c. Cyclic aromatic groups that lie perpendicular to the planar
aromatic backbone.
d. Improved solubility with no sacrifice of thermal properties. 1 2
POLYMER CHEMISTRY

25. D. Cycloaddition to make cyclic repeating unit.
Tg = 215oC
Tg = 265oC
SCHEME 4.1. Increasing Tg of a polyquinoxaline by intramolecular cycloaddition.

26. E. Oligomers with reactive End Group.
TABLE 4.4. Some Reactive End Groups for Converting Oligomers to Network Polymers
Type Sturcture
Cyanate
Ethynyl
Maleimide
Nadimidea
Phenylethynyl
aCommon name for 5-norbornene-2,3-dicarboximide.

27. 4.5 Flammability and Flame Resistance.
A. Process of flame propagation.
  Solid polymer -(heat)→ Depolymerization to monomer(radical
 formation) → Degradation to combustable gas → Flame formation.
FIGURE Representation of polymer combustion , gas diffusion; ,
heat flux. [Adapted from Factor.43]
Diffusion
zone
Flame
front
Pyrolysis
Solid
polymer

28. 4.5 Flammability and Flame Resistance.
B. The object of flame retardation.
a. Suppression of smoke and toxic gases.
b. Development of nonflammable polymer: self-extinguishing.
C. The strategies of flame resistance.
a. Retarding the combustion process in the vapor phase.
b. Causing "char" formation in the pyrolysis zone.
c. Giving nonflammable gas or cooling the pyrolysis zone.
POLYMER CHEMISTRY

29. 4.5 Flammability and Flame Resistance.
D. Examples of flame resistance.
a. Halogen containing polymer: to suppress radical concentration.
b. Addition antimony oxide to be formed antimony halide.
c. Phosphorus-containing polymers: promotion char.
d. Aromatic and network polymers: to promote char.
e. Addition Al2O3 · 3H2O to evolve water.
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30. 4.6 Chemical Resistance. A. Types of chemical reaction.
a. Free radical reaction by oxygen or UV-light.
b. Hydrolysis.
c. Ozonolysis.
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31. 4.6 Chemical Resistance. B. Preventing hydrolysis.
a. Chemically resistant polyester formulations. 7 8
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32. 4.6 Chemical Resistance. B. Preventing hydrolysis.
  b. End group blocking.
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33. C. Moisture resistance and chemical inertness: fluorinated polymer.
 a. Fluorinated phosphazene. 9 10
b. Teflon and copolymer. 11 12 13
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34. D. Ozonolysis a. Ozonolysis mechanism.
a. Ozonolysis mechanism.
b. Preventing ozonolysis: to add cyclopentadiene. 14
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35. 4.6 Chemical Resistance. E. Sunlight protection. F. Morphology
 Monomers containing ultraviolet-absorbing chromophore. 15
F. Morphology
       
a. Crystallinity
                       to prevent penetration.
  b. Crosslinking
POLYMER CHEMISTRY

36. 4.7 Degradability A. Application for polymer degradability.
a. Polymer waste treatment.   
1) Photodegradable polymer containing carbonyl functional group.
      Norrish type II degradation reaction.
2) Biodegradable polymer by microbiology.
      Poly(α-hydroxybutanoic acid), starch+PE
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37. A. Application for polymer degradability.
b. Photoresist for IC.
  1) Positive resists: radiation promotes degradation of the resist
                    exposed by the mask.
 2) Negative resists: radiation makes insoluble network.
FIGURE Schematic of a typical procedure for producing (a) negative resists and (b) positive resists in the manufacture of integrated circuits.

38. A. Application for polymer degradability.
c. Agricultural degradable mulches.
 1) Starch-graft-poly(methylacrylate).
 2) Block copolymers of amylose or cellulose with polyester.
d. Surgical sutures and implanted polymeric matrix devices.
POLYMER CHEMISTRY

39. B. Controlled release: penetration rather than degradation.
a. Microencapsulation.
b. Strip.
FIGURE Membrane-controlled release devices: (a) microencapsulation, and (b) strip.
POLYMER CHEMISTRY

40. B. Controlled release: penetration rather than degradation.
c. 2,4-Dichlorophenoxyacetic acid(2,4-D): herbicide.
   Vinyl polymer with hydroyzable pendant group, chelate with iron.
d. Pheromone release strips: insecticides.
e. Transdermal patches.   
1) Nitroglycerin to treat angina.
2) Scopolamine to treat combat motion sickness.
POLYMER CHEMISTRY

41. B. Controlled release: penetration rather than degradation.
f. Phosphazene polymer.
         
R= amino acids, esters, steroids
g. Poly(N-isopropylacrylamide)   
1)      
2) To shrink reversibly in response to temperature increase.
3) Incorporation with IPN.
POLYMER CHEMISTRY

42. 4.8 Electrical Conductivity
A. Classification of electrical conductivity.
 a. Insulator : σ < 10-8 S/ cm
 b. Semiconductor: 10-7 < σ < 10-1 S/ cm
c. Conductor: σ > 102 S/ cm
    (σ=conductivity,  S (simen)= 1/Ω)
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43. B. Theory of electrical conductivity for polyacetylene.
a. Soliton.
  1) Delocalization regions of conjugated double bond.
  2) Extend about 15 bond lengths.
  3) Energy gain arising for stabilization.
  4) Electron transfer via positive or negative solitons
FIGURE4.14. Proposed conducting unit of polyacetylene. Soliton may be neutral (radical), positive
(carbocation), or negative (carbanion).
Soliton

44. B. Theory of electrical conductivity for polyacetylene.
b. Doping: incorporation dopant much as AsF5, I2, Lewis acid, etc.
                                     
 + dopant : 1.5×105 S/cm 22 23 2
CH CH [ ]
+ 3 I2 +
+ 2 I3- -
+ Na
+ Na+
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45. C. Example of conducting polymers.
      
 a. Poly(N-vinyl-carbazole)
1) Photoconducting: conduct small degree of     
electricity under the light.
 2) Electrophotography(photocopying) 19
 b. Poly(sulfur nitride): Super conductor 20
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46. C. Example of conducting polymers.
c. Polyaniline          Polypyrrole         Polythiophene  
                       
    
Poly(p-phenylene)      Poly(p-phenylenevinylene)
                        
d. Conducting polymers to be used as light emitting diode.
 (PPV)
  C. Example of conducting polymers. 24 25 26 28 27
e. Conducting polymers much lower density than metal.
    polymer=1g/cm3, copper=8.92g/cm3, Gold=19.3g/cm3
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47. Poly(p-phenylenevinylene) Polyaniline Polypyrrole Polythiophene
TABLE 4.5. Conductivities of Metals and Doped Polymersa
Material
Copper
Gold
Polyacetylene
Poly(sulfur nitride)
Poly(p-phenylene)
Poly(p-phenylenevinylene)
Polyaniline
Polypyrrole
Polythiophene
5.8  105
4.1  105
103 – 105
103 – 104
103
102 – 103
102
Conductivity (S/cm)b
aData from J. R. Reynolds, A. D. Child, and M. B. Gieselman, in
Encyclopedia of Chemical Technology, 4th ed. (J. I. Kroschwitz
and M. Howe-Grant, Eds.), Wiley, New York, 1994; and Chem.
Eng. News, Jume 22, 1987, p. 20.
bI siemen (S) = I ohm-1.
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48. 4.8 Electrical Conductivity
D. Polyelectrolytes for solid battery.                  30 29
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49. 4.9 Nonlinear Optical Properties
A. Photonics device.
 a. Information and image processing.
 b. To operate higher rate.
 c. To store information much more densely.
POLYMER CHEMISTRY

50. 4.9 Nonlinear Optical Properties
B. NLO materials
a. Inorganic and low molecular weight organic compounds.
b. Polymeric materials   
1) Conjugated double bond like conducting polymer:
     Third order harmonic generation.
   
2) Asymmetric strong dipole aromatic molecule:
      Second order harmonic generation
3) Containing strong electrowithdrawing and donating group:
      Second order chromophore.
4) Dipole molecules must be poled at Tg.
5) Stabilizing poled molecule to avoid relaxation.
POLYMER CHEMISTRY

51. 31 32

52. 4.9 Nonlinear Optical Properties
C. Producing NLO polymeric material.
a. Host-Guest combination.
    Host: matrix polymer.
    Guest: NLO chromophore.
 b. Incorporating chromophore in the polymer backbone or side
    chain covalently.
POLYMER CHEMISTRY

53. 4.10 Additives A. Purpose of using additives.
a. To alter the properties of the polymer.
b. to enhance processability.
B. Types of polymer additives.
C. Examples of polymer additives.
a. Plasticizer.
1) Internal plasticizer, to have covalent bonds between polymer
      and plasticizer.
 2) External plasticizer, physical mixture with plasticizer.
POLYMER CHEMISTRY

54. TABLE 4.6. Polymer Additives
Type
Mechanical property modifiers
Plasticizers
Impact modifiers
Reinforcing fillers
Nucleating agents
Surface property modifiers
Slip and antiblocking agents
Lubricants
Antistatic agents
Coupling agents
Wetting agents
Antifogging agents
Chemical property modifiers
Flame retardants
Ultraviolet stabilizers
Antioxidants
Biocides
Aesthetic property modifiers
Dyes and pigments
Odorants
Deodorants
Processing modifiers
Slip agents and lubricants
Low-profile additives
Thickening agents
Heat stabilizers
Defoaming agents
Blowing agents
Emulsifiers
Crosslinking (curing) agents
Promoters
Increase flexibility
Improve impact strength
Increase strength properties
Modify crystalline morphology
Prevent film and sheet sticking
Prevent sticking to machinery
Prevent static charge on surfaces
Improve bonding between polymer and filler
Stabilize dispersions of filler
Disperse moisture droplets on films
Reduce flammability
Improve light stability
Prevent oxidative degradation
Prevent mildew
Impart color
Add fragrance
Prevent development of odor
Improve light transmission
Reduce melt viscosity
Prevent sticking to processing machinery
Prevent shrinkage and warpage
Increase viscosity of polymer
solutions or dispersions
Prevent degradation during processing
Reduce foaming
Manufacture stable foams
Stabilize polymer emulsions
Crosslink polymer
Speed up crosslinking (curing)
Function

55. b. TABLE 4.7. Commonly Used Plasticizers Aromatic
Di-2-ethylhexyl phthalate
Di-n-octyl phthalate
Di-i-octyl phthalate
Di-i-decyl phthalate
Di-n-undecyl phthalate
Di-n-tridecyl phthalate
Tri-2-ethylhexyl trimellitate
Aliphatic
Di-2-ethylhexyl adipate
Di-2-ethylhexyl sebacate
Di-2-ethylhexyl azelate
Epoxy
Epoxidized linseed oil
Epoxidized soya oil
Polymeric
Poly(alkylene adipates, sebacates, or azelates)
Fire retardant
Chlorinated paraffins
Phosphate esters
 b.
POLYMER CHEMISTRY

56. C. Producing NLO polymeric material.
c. Reinforcing material: Composite.
 1) Carbon black for tire.
 2) Glass fiber for FRP.
 3) Aromatic polyamide or graphite fiber for high performance
      engineering plastic.
POLYMER CHEMISTRY