CHM 585 490 Chapter 10

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CHM 585 / 490Chapter 10

• PVC
• PP
• Polyurethanes
• Phenolic resins
• PS
• ABS

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PVC

• 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

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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

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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
  indoor-outdoor 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

• 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
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Polyolefin Evolution
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Polyolefin Evolution
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Polyolefin Evolution
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Today

• Estimated that gt 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

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Polyurethane uses

• 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 gt P)
• novolac (acidic conditions ....F lt 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
Atactic
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Anionic Polymerization
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Cationic
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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

• 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

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What do they bring to the party?

• Acrylonitrile
• Heat stability
• Chemical resistance
• Butadiene
• Toughness
• Impact resistance
• Styrene
• Stiffness
• Processability