CHM 585 / 490
Chapter 10
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PVC
PP
Polyurethanes
Phenolic resins
PS
ABS
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PVC
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Second largest (after polyethylene)
Globally 25 million tonnes
14B pounds in U.S.
Very versatile
Strength, transparency, low cost
½ of the polymer is not based upon petrochemical
feedstock
Cl
(
H
H
C C
H
Cl
)
n
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PVC Processes
• All from free radical reactions
• Most common is batchwise aqueous
suspension process
– Up to 50,000 gallons of monomer agitated as a
suspension in water, centrifuged and dried
– High bulk density porous particles obtained
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•Vinylchloride monomer is dispersed in water by agitation.
Polymerization starts by adding monomer-soluble initiators and
addition of suspension stabilizers and suspending agents
minimizes coalescence of the grains.
•The reaction temperature is used for the control of the Mw and
varies between 45 - 75 °C. Reactor pressure is between 800 1200 kPa.
•The remaining monomer is stripped from the polymer with
steam. The waste water is separated in a centrifuge. The PVC
resin is dried with hot air and stored.
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•Emulsion polymerization; batch, semi-continuous or continuous.
Vinylchloride monomer is emulsified in water by means of
surface-active agents. The monomer is thus present as droplets
and a small fraction is dissolved in micelles. Water-soluble
initiator is added and polymerization starts in the micelles.
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Micelles
• Are spherical aggregates in a dispersion
• Are formed when molecules that possess a
hydrophobic region and a hydrophilic
region are placed in water
• Are responsible for the cleansing action of
soaps and detergents
• CH3(CH2)16CO2-Na+
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Emulsion Polymerization of PVC
•Monomer is added to the latex particles (=micelles) by diffusion
from the emulsion droplets through the aqueous phase.
Batch: all components in reactor; polymerization is stopped when
the yield is reached.
Semi-continuous: emulsifier is continuously added during the
polymerization.
Continuous: water, initiator, monomer and emulsifier are added at
the top of the reactor. The PVC latex is removed at the bottom of
the reactor. The latex is degasified and dried; the resulting solid
PVC is stored.
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Plasticizers
• About 2 billion pounds of plasticizers used
in U.S.
• About 90% for PVC
• Most are esters
– Commonly esters of phthalic anhydride, adipic
acid, phosphoric acid
O
O
O
O
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PP
• Used to make things like dishwasher-safe food
containers. It can do this because it doesn't melt
below 160 oC. Polyethylene will melt at around 100
oC, which means that polyethylene dishes will warp
in the dishwasher.
• As a fiber, polypropylene is used to make indooroutdoor carpeting, the kind that you always find
around swimming pools and miniature golf courses.
It works well for outdoor carpet because it is easy to
make colored polypropylene, and because
polypropylene doesn't absorb water, like nylon does.
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Polypropylene
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Ziegler-Natta
Typical system: TiCl4 / MgCl2 / Et3Al
90 – 97% isotactic PP
Remainder is atactic and is removed in a
separate step
• North America PP consumption = 17B
pounds / year
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Stereoregular Polypropylene
Isotactic polypropylene
Syndiotactic polypropylene
Atactic Polypropylene
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Polyolefin Evolution
M(CH3)2
Kaminsky and Sinn- late70s
Atactic PP
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Polyolefin Evolution
1985 Ewen at Exxon
Isotactic PP
M(CH3)2
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Polyolefin Evolution
M(CH3)2
Ewen 1988
Syndiotactic PP
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Today
• Estimated that > $ 4 Billion spent to date on
polypropylene research
• Many exciting developments in metallocene
catalysis - Changing views about the need
for cyclopentadienyl type ligands and
extension beyond Group IV metals.
• Very active research area!
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Polyurethanes
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•The urethane linkage looks like
this:
(looks like ester)
•A wide variety of molecular sections which
may be inserted between urethane links
provides highly diversified polyurethane
properties.
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Here are some commonly used isocyanates:
Isocyanate
Abbreviation Structure
Toluene 2,4-diisocyanate
TDI
Toluene 2,6 diisocyanate
TDI
Naphthalene diisocyanate
NDI
Diphenyl methane diisocyanate
MDI
Hexamethylene diisocyanate
HDI
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Polyurethane uses
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Upholstered furniture
Mattresses
Automobiles
Footwear
Paints
Adhesives
Spandex
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Industry sources peg DuPont's annual sales of Lycra at more
than $1.5 billion.
DuPont's has the lion's share of world spandex capacity at
about 200 million lb annually.
In the U.S., those other producers include Fall River, Mass.based Globe Manufacturing, maker of Glospan and Cleerspan
spandex, and Bayer Corp. --the U.S. affiliate of Germany's
Bayer--maker of Dorlasten brand spandex.
Bayer also makes spandex in Germany. Other world producers
include Japan's Asahi Chemical Industry and Toyobo, and
South Korea's Tae Kwang Industrial Co.
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Spandex Type
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Phenolic Resins
Phenol-formaldehyde ("phenolic") resins are the oldest completely
synthetic polymer. (1907 Leo H. Baekeland patents). These thermoset
polymers exhibit:
•Excellent thermal stability
•High char yield
•Low smoke generation
•Low smoke toxicity
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Most phenolic resins are made using phenol (P) and formaldehyde (F).
They are divided into two classes:
•resoles (alkaline conditions...F > P)
•novolac (acidic conditions ....F < P)
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Cure of resole prepolymer proceeds under neutral or acidic conditions
and at elevated temperature.
•Crosslinking occurs via the continued formation of methylene links
and the formation of dibenzyl ether linkages.
•Higher temperatures favor the formation of methylene bridges
•Both are condensation reactions and produce water
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• About 150 million pounds sold in North
America
• Ideal for applications where physical
properties and structural integrity must be
maintained at elevated temperatures
• Automotive transmission spacers and brake
pads, kitchen range temperature controls,
rocket nozzles and heat shields
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Polystyrene
• Free radical polymerization
– Preferred industrial route
– atactic
• Anionic polymerization
– atactic
• Cationic Polymerization
– atactic
• Organometallic polymerization
– Ziegler-Natta / metallocene
– Syndiotactic or isotactic
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Radical Polymerization
R
.
R
.
R. +
R
.
( H2C
Atactic
CH
)
n
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Anionic Polymerization
R
-
CH3CH2CH2CH2- Li+ +
R
-
( H2C
CH
)
n
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Cationic
+
+
BF3or AlCl3
trace water
+
( H2C
CH
)
n
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Organometallic
• Ziegler-Natta (TiCl3 / triethylaluminum)
– Isotactic
• Melting point of 240C
• Slowly crystallizes
• Opaque
• Metallocene
– Syndiotactic
• Melting point 270C
• Crystallizes rapidly
• Opaque
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GPPS
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General purpose polystyrene
Clear, amorphous polymer
Lower density than PC
Noncrystalline so less mold shrinkage than
polyethylene, polypropylene, or PET
• Relatively high modulus
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HIPS
• High Impact Polystyrene
• Styrene polymerized in the presence of
rubber ( polybutadiene) particles to give
polystyrene with rubber dispersed
throughout the polymer
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Some styrene grafts onto
butadiene polymer and
compatibilizes the blend
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ABS
• Terpolymer of acrylonitrile / butadiene /
styrene
CN
A
B
S
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What do they bring to the party?
• Acrylonitrile
– Heat stability
– Chemical resistance
• Butadiene
– Toughness
– Impact resistance
• Styrene
– Stiffness
– Processability
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