slide1 n.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Chapter 4. Chemical Structure and Polymer Properties PowerPoint Presentation
Download Presentation
Chapter 4. Chemical Structure and Polymer Properties

Loading in 2 Seconds...

play fullscreen
1 / 56

Chapter 4. Chemical Structure and Polymer Properties - PowerPoint PPT Presentation


  • 462 Views
  • Uploaded on

POLYMER CHEMISTRY . 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

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Chapter 4. Chemical Structure and Polymer Properties' - vito


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
slide1

POLYMER CHEMISTRY

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

slide2

POLYMER CHEMISTRY

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.

slide3

FIGURE 4.1. Compression molding

POLYMER CHEMISTRY

4.2 Fabrication Methods.

A. Molding

a. Compression molding : thermoset polymer.

slide4

FIGURE 4.2. Injection molding. [Reprinted from V. Hopp and I. Hennig, Handbook of Industrial

Chemistry, copyright 1938, courtesy of McGraw-Hill.]

POLYMER CHEMISTRY

b. Injection molding : thermoplastic polymer.

slide5

FIGURE 4.3. Basic components of a reaction injection molding (RIM) process.

[From Modern Plastics Encyclopedia, 1984-85. Reprinted with permission of Modern Plastics.]

POLYMER CHEMISTRY

c. Reaction injection molding (RIM)

newly developed molding.

   polyurethane and other polymer system.

slide6

FIGURE 4.4. Blow molding. [Courtesy of the Society of the Plastics, Inc.]

POLYMER CHEMISTRY

A. Molding

d. Reinforced reaction injection mold (RRIM) :

Modified RIM for fiber reinforcement.

e. Blow molding : for bottles.

slide7

POLYMER CHEMISTRY

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.

slide8

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.

slide9

POLYMER CHEMISTRY

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.

slide10

POLYMER CHEMISTRY

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.

slide11

Property

Viscosity

Working

range

Molecular weight

Nonmechanical

Mechanical

FIGURE 4.6. Dependence of properties on molecular weight

(hypothetical polymer).

slide12

POLYMER CHEMISTRY

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

slide13

F

 =

l

 =

A

l

E =

POLYMER CHEMISTRY

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)

c. Unit of modulus

same unit of tensile strength.

d. Unit of elongation :No dimension.

slide14

Fiber

Brittle

plastic

Stress

()

Elastomer

Strain ()

FIGURE 4.7. Characteristics of tensile stress-strain behavior.

slide15

Elongation at break

Elongation

at yield

Stress

()

Yield

stress

Strain ()

Ultimate

strength

FIGURE4.8. General tensile stress-strain curve for a typical thermoplastic.

slide16

Glassy

9

Rubbery

log E

(N/m2)

6

Flow

Tg

3

Temperature

FIGURE 4.9. Effect of temperature on tensile modulus of an amorphous thermoplastic;

log E, modulus scale; Tg, glass transition temperature.

D. Temperature dependent mechanical properties

a. The modulus of amorphous thermoplastic depend on temperature.

slide17

Crystalline

9

Highly

crosslinked

log E (N/m2)

6

Lightly

crosslinked

Low

molecular

weight

High

molecular

weght

3

Tm

Temperature

FIGURE 4. 10. 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).]

 b. Tensile modulus of crystalline and crosslink polymer depend on temperature.

slide18

POLYMER CHEMISTRY

4.3 Mechnical Properties

E. Time dependent mechanical properties

a. viscoelastic property       

b. creep stress relaxation   

>

disentanglement by stress like astemperature

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.

slide19

TABLE 4.1. Mechanical Properties of Common Homopolymersa

Impact

Strengthc

(N/cm)

No break

0.23-2.3

0.23-0.57

0.23-1.3

0.20-0.26

0.17-0.34

1.7

0.46-1.2

0.14-0.37

9.1

Compressive

Strengthb

(Mpa)

-

20-25

38-55

55-90

83-90

72-124

12

103

76-103

86

Flexural

Strengthb

(Mpa)

-

-

41-55

69-110

69-101

72-131

-

42-117

96-124

93

Tensile Properties at Break

Property

Modulusb

(Mpa)

172-283

1070-1090

1170-1720

2410-4140

2280-3280

2240-3240

400-552

-

2760-4140

2380

Elongation

(%)

100-650

10-1200

100-600

40-80

1.2-2.5

2-10

200-400

60-300

50-300

110

Strengthb

(Mpa)

8.3-31

22-31

31-41

41-52

36-52

48-76

14-34

76-83

48-72

66

Polymer

Polyethylene,

low density

Polyethylene,

high density

Polypropylene

Poly(vinyl chloride)

Polystyrene

Poly(methyl

methacrylate)

Polytetra-

fluoroethylene

Nylon 66

Poly(ethylene

terephthalate)

Polycarbonate

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.

slide20

TABLE 4.2. Fiber Propertiesa

Specific

Gravity

1.50

1.30

1.38

1.14

1.44

1.43

0.90

0.95

2.56

7.7

Tenacityb

(N/tex)

0.26-0.44

0.09-0.15

0.35-0.53

0.40-0.71

1.80-2.0

0.27

0.44-0.79

2.65d

0.53-0.66

0.31

Fiber Type

Natural

Cotton

Wool

Synthetic

Polyester

Nylon

Aromatic polyamide

(aramid)c

Polybenzimidazole

Polypropylene

Polyethylene (high strength)

Inorganicc

Glass

Steel

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. 647-733.

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.

slide21

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

slide22

POLYMER CHEMISTRY

TABLE 4.3. Representative Thermally Stable Polymersa

Decomposition

Temperature (oC)b

585c

570

490

490

Type

Polyimide

Poly(phenylene oxide)

Polythiadiazole

Poly(phenylene sulfide)

Structure

aData from Korshak17

bNitrogen atmosphere unless otherwise indicated.

cHelium atmosphere.

slide23

POLYMER CHEMISTRY

B. Aromatic or cyclic repeating unit

a. Thermal stability : to bonds cleavage for degradation

b. Poor processability

1) High Tgor 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

slide24

POLYMER CHEMISTRY

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

slide25

D. Cycloaddition to make cyclic repeating unit.

Tg= 215oC

Tg= 265oC

SCHEME 4.1. Increasing Tg of a polyquinoxaline by intramolecular cycloaddition.

slide26

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.

E. Oligomers with reactive End Group.

slide27

Diffusion

zone

Solid

polymer

Flame

front

Pyrolysis

zone

FIGURE 4.11. Representation of polymer combustion. , gas diffusion; ,

heat flux. [Adapted from Factor.43]

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.

slide28

POLYMER CHEMISTRY

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.

slide29

POLYMER CHEMISTRY

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.

slide30

POLYMER CHEMISTRY

4.6 Chemical Resistance.

A. Types of chemical reaction.

a. Free radical reaction by oxygen or UV-light.

b. Hydrolysis.

c. Ozonolysis.

slide31

7

8

POLYMER CHEMISTRY

4.6 Chemical Resistance.

B. Preventing hydrolysis.

a. Chemically resistant polyester formulations.

slide32

POLYMER CHEMISTRY

4.6 Chemical Resistance.

B. Preventing hydrolysis.

b. End group blocking.

slide33

POLYMER CHEMISTRY

C. Moisture resistance and chemical inertness: fluorinated polymer.

 a. Fluorinated phosphazene.

9

10

b. Teflon and copolymer.

13

11

12

slide34

14

POLYMER CHEMISTRY

D. Ozonolysis

a. Ozonolysis mechanism.

b. Preventing ozonolysis: to add cyclopentadiene.

slide35

POLYMER CHEMISTRY

4.6 Chemical Resistance.

E. Sunlight protection.

 Monomers containing ultraviolet-absorbing chromophore.

15

F. Morphology

a. Crystallinity

                       to prevent penetration.

  b. Crosslinking

slide36

POLYMER CHEMISTRY

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

slide37

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 4.12. Schematic of a typical procedure for producing (a) negative resists and (b) positive resists in the manufacture of integrated circuits.

slide38

POLYMER CHEMISTRY

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.

slide39

POLYMER CHEMISTRY

B. Controlled release: penetration rather than degradation.

a. Microencapsulation.

b. Strip.

FIGURE 4.13. Membrane-controlled release devices: (a) microencapsulation, and (b) strip.

slide40

POLYMER CHEMISTRY

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.

slide41

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

B. Controlled release: penetration rather than degradation.

slide42

POLYMER CHEMISTRY

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)

slide43

Soliton

FIGURE4.14. Proposed conducting unit of polyacetylene. Soliton may be neutral (radical), positive

(carbocation), or negative (carbanion).

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

slide44

]

]

[

[

2

+ 2 I3-

CH CH

+ 3 I2

2

CH CH

·

+

]

+ Na

[

CH CH

]

+ Na+

[

CH CH

·

-

23

22

POLYMER CHEMISTRY

B. Theory of electrical conductivity for polyacetylene.

b. Doping: incorporation dopant much as AsF5, I2, Lewis acid, etc.

 + dopant : 1.5×105 S/cm

slide45

19

POLYMER CHEMISTRY

  C. Example of conducting polymers.

 a. Poly(N-vinyl-carbazole)

1) Photoconducting: conduct small degree of     

electricity under the light.

 2) Electrophotography(photocopying)

 b. Poly(sulfur nitride): Super conductor

20

slide46

c. Polyaniline          Polypyrrole         Polythiophene  

Poly(p-phenylene)      Poly(p-phenylenevinylene)

d. Conducting polymers to be used as light emitting diode.

 (PPV)

POLYMER CHEMISTRY

  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

slide47

TABLE 4.5. Conductivities of Metals and Doped Polymersa

5.8  105

4.1  105

103– 105

103 – 104

103

103

102– 103

102 – 103

102

Material

Copper

Gold

Polyacetylene

Poly(sulfur nitride)

Poly(p-phenylene)

Poly(p-phenylenevinylene)

Polyaniline

Polypyrrole

Polythiophene

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.

POLYMER CHEMISTRY

slide48

POLYMER CHEMISTRY

4.8 Electrical Conductivity

D. Polyelectrolytes for solid battery.

30

29

slide49

POLYMER CHEMISTRY

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.

slide50

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

4.9 Nonlinear Optical Properties

slide51

31

32

slide52

POLYMER CHEMISTRY

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.

slide53

POLYMER CHEMISTRY

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.

slide54

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

Nucleating agents

Processing modifiers

Plasticizers

Slip agents and lubricants

Low-profile additives

Thickening agents

Heat stabilizers

Defoaming agents

Blowing agents

Emulsifiers

Crosslinking (curing) agents

Promoters

Function

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)

slide55

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

POLYMER CHEMISTRY

 b.

slide56

POLYMER CHEMISTRY

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.