polymers
TRANSCRIPT
CHAPTER 13Polymers
A molded engineering polymer serves as a light-weight and cost-effective air-intake manifoldfor automotive appliations. (Courtesy of SolvayAutomotive, Inc., Troy, Michigan.)
C C
H
H
Cl
H
C
Cl
H
C
H
H
C
Cl
H
C
H
H
C
Cl
H
C
H
H
C C
H
H
C C
H
H
C C
H
H
mer
Monomer
PolymerC C
H
H
Cl
H
Cl
H
Cl
H
Cl
H
Figure 13-1 Polymerization is the joining of indi-vidual monomers (e.g., vinyl chloride, C2H3Cl)to form a polymer [(C2H3Cl)n] consisting ofmany mers (again, C2H3Cl).
Termination
Growth
Initiation
C C
H
H
C C OH
H
H
H
H
H
H
C C
H
H
C C
H
H
H
H
H
H
HO(n ′) C C
H
H
H
H
C C
H
H
C C• + OH•
H
H
H
H
H
H
C C
H
H
C C
H
H
H
H
H
H
HO(n) C C
H
H
H
H
C C
H
H
C
H
H
H
H
H
H
HO(3) C C
H
H
H
H
C
H
H
H
H
HO(2) C C
H
H
H
H
HO(1′) C C•
C•
C•
H
H
H
H
(1) C
H
H
H
H
OH• + C
Figure 13-2 Detailed mechanism of polymerization by a chain growth pro-cess (addition polymerization). In this case, a molecule of hydrogenperoxide, H2O2, provides two hydroxyl radicals, OH•, which serve toinitiate and terminate the polymerization of ethylene (C2H4) to polyethy-lene ( C2H4 ) n. [The large dot notation (•) represents an unpairedelectron. The joining, or pairing, of two such electrons produces a co-valent bond, represented by a solid line (—).]
… …
C C
H
H
C C
H
H
C C
H
H
C C
H
H
H
H
H
H
H
H
Cl
H
C C
H
H
C C
H
H
C C
H
H
C C
H
H
Cl
H
H
H
H
H
H
H
C C
H
H
C C
H
H
C C
H
H
C C
H
H
H
H
Cl
H
Cl
H
Cl
H
ethylene ethylene vinyl chloridevinyl chloride
Figure 13-3 A copolymer of ethylene and vinyl chloride is analogous to a solid-solution metal alloy.
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…
…
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…
…
…
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
HC
H
HC
H
HC
H
HC
H
H
C
H
H
C
H
H
C
H
HC
H
HC
H
HC
H
HC
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H C
H
H
C
H
H
C
H
H
C
H
HC
H
HC
H
H
C
Cl
H
C
H
H
C
Cl
H
C
H
H
C
Cl
H
C
H
HC
Cl
HC
H
HC
Cl
HC
H
HC
Cl
H
C
Cl
H
C
H
H C
Cl
H
C
H
H C
Cl
H
C
H
H C
Cl
H
C
H
H C
Cl
H
C
H
H
C
Cl
HC
H
HC
Cl
HC
H
H
C
Cl
H
C
H
HC
Cl
H
C
H
H
Figure 13-4 A blend of polyethylene and polyvinyl chloride is analogous to a metal alloy with limitedsolid solution.
C O
H
H
C O
H
H
C O
H
H
C O
H
H
C O
H
H
C O
H
H
C O
H
H
mer
Monomer
PolymerC O
H
H
Figure 13-5 The polymerization of formaldehydeto form polyacetal. (Compare with Figure 13–1.)
HO
H
HH
H
H
H
H H
OH
H
H
H
H
H
OH
H
H
H
H
HO
H
H
H
H
H
+
O
CC
CC
C
C C
CC
C
C
C
CC
C
C
C
CH2O
CC
C
C
C C
C
C
Formaldehyde
Phenols
Figure 13-6 Single, first step in the formation of phenol-formaldehyde by a step growth pro-cess (condensation polymerization). A water molecule is the condensation product.
H
C Bridge from formaldehyde
Former phenol,
H
H
H
OH
H
H H
Figure 13-7 After several reaction steps like that in Figure 13–6, polyfunc-tional mers form a three-dimensional network molecular structure. (FromL. H. Van Vlack, Elements of Materials Science and Engineering, 4thEd., Addison-Wesley Publishing Co., Inc., Reading, Mass., 1980.)
A fibrous bundle of natural collagen is shown attached to the sur-face of synthetic hydroxyapatite granules in a bioceramic implant.(From J.P. McIntyre, J.F. Shackelford, M.W. Chapman, and R.R.Pool, Bull. Amer. Ceram. Soc. 70 1499 (1991))
Tropo-collagenmolecule
Tropo-collagenmolecules
Micro-fibril
Sub-fibril
Fibril
Fibrilsinregister
64 nm
alpha 2
alpha 1 chains
280 nm
Schematic illustration of the polymeric structure of collagen inbone. (From R.B. Martin, “Bone as a Ceramic Composite Mate-rial,” in Bioceramics—Applications of Ceramic and Glass Mate-rials in Medicine, Ed. J.F. Shackelford, Trans Tech Publications,Switzerland, 1999)
0 500 1000Degree of polymerization, n
1500
Popu
lati
on d
ensi
ty
Figure 13-8 Statistical distribution of molecular lengths in agiven polymer as indicated by n, the degree of polymer-ization.
C
C
L
CC
109.5˚
Rotatable bond
Figure 13-9 The length of kinked molecularchain is given by Equation 13.4, due tothe free rotation of the C—C—C bondangle of 109.5◦.
109.5˚
Figure 13-10 “Sawtooth” geometry of a fully extended molecule. The relative sizes of carbon and hydrogen atomsare shown in the polyethylene configuration.
R R R R R R R R R R
R
R
R
R
R
R
R
R
R
R
R R
R
R R
R R R RR
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C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
C
H
H
C
H
C
H
H
C
H
C
H
H
C
H
C
H
H
C
(a)
(b)
H
C
H
H
C
H
C
H
H
C
H
C
H
H
C
H
C
H
H
C
H
C
H
H
C
H
C
H
H
C
H
C
H
H
C
H
C
H
H
C
H
C
H
H
C
H
C
H
H
C
(c)
H
C
H
H
C
H
C
H
H
C
H
C
H
H
C
H
C
H
H
C
H
C
H
H
C
H
C
H
H
C
H
C
H
C
H
H
C
H
H
C
H
H
C
H
C
H
C
H
H
C
H
H
C
H
C
H
H
C
H
C
H
H
C
H
C
H
C
H
H
C
H
C
H
H
C
H
(d)
Figure 13-11 (a) The symmetrical polyethylene molecule. (b) A less symmetricalmolecule is produced by replacing one H in each mer with a large side group,R. The isotactic structure has all R along one side. (c) The syndiotactic struc-ture has the R groups regularly alternating on opposite sides. (d) The least sym-metrical structure is the atactic, in which the side groups irregularly alternateon opposite sides. Increasing irregularity decreases crystallinity while increas-ing rigidity and melting point. When R = CH3, parts (b)–(d) illustrate var-ious forms of polypropylene. (One might note that these schematic illustra-tions can be thought of as “top views” of the more pictorial representations ofFigure 13–10.)
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… C
H
H
C
H
H
C
H
HC
H
HC
H
HC
H
H
C
H
H
C
H
H H
HC
H
C
H HC
H HC
H HC
H HC
H HC
H HC
H HC
H HC
C
H
HC
H
H
C
H
H
C
H
H
C
H
HC
H
HC
H
HC
H
H C
H
HC
H
H
Figure 13-12 Branching involves adding a polymeric molecule to the side of the mainmolecular chain.
n
CH3
CH3
O
Clamp limit switches Mold areaOperator’scontrol station
Operator’s gate Hydraulic control station Electric control panel
Feederhopper Injector limit
switchesClamp
Figure 13-13 Injection molding of a thermoplastic polymer. (After Modern Plastics Encyclopedia, 1981–82, Vol. 58, No. 10A, McGraw-Hill Book Company, New York, October 1981.)
Large rectangular feed openingHopper
Barrel heating and cooling
Feed throat
Rear seatSide vent
Heavy wall cylinder
Hinged swing gate
Product
Pressuremeasurement
Front barrel support
Electrical box
TrapVacuum pumpMotor
Barrel water cooling systemExtruder base
Large air spacer
Change gears
Rotary union
Gear reducer
Thrust bearing assembly
Figure 13-14 Extrusion molding of a thermoplastic polymer. (After Modern Plastics Encyclopedia, 1981–82, Vol. 58, No. 10A, McGraw-Hill Book Company, New York, October 1981.)
Mold area
Figure 13-15 Blow molding of a thermoplastic polymer. The specific shaping operation is sim-ilar to the glass container process of Figure 12–3. (After a Krupp-Kautex design.)
Flash-type mold
Product
Figure 13-16 Compression molding of a thermosetting poly-mer. (After Modern Plastics Encyclopedia, 1981–82, Vol.58, No. 10A, McGraw-Hill Book Company, New York,October 1981.)
Pot
Plunger
Parting line for cull
Cavity partingline
Figure 13-17 Transfer molding of a thermosetting polymer. (After ModernPlastics Encyclopedia, 1981–82, Vol. 58, No. 10A, McGraw-Hill BookCompany, New York, October 1981.)
The
rmal
heat
Cra
ckin
g
Cut
ting
Pel
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Slab
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Stri
p
Stra
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Test
tank
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eal
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p
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bury
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poun
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mat
eria
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Col
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trip
or
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up
com
poun
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Pla
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ator
Wir
e an
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cabl
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bers
War
min
g
Fabr
ic d
ip
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wea
r
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good
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Coa
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fabr
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icti
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otar
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ss
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d tu
mbl
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Trim
min
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Fla
sh r
emov
al
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rude
r
Stor
age
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embl
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ulca
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r
Vul
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alen
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amin
atin
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trud
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ead
insu
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scu
ttin
gB
uild
ing
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cani
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Cal
ende
r
Coo
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Tube
rP
ans
Ope
n st
eam
vul
cani
zer
Ree
ls
Figure 13-18 Typical flow diagram for the manufacturing of variouscommon rubber goods. (From the Vanderbilt Rubber Handbook,R. T. Vanderbilt Co., Norwalk, Conn., 1978.)