Polymerization

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Polymerization

• Section 7

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Polymerization

• The process of chemically linking monomers
  together to form macromolecules
• In our discussion we will not include natural
  polymers
• Essentially there are two types of polymerization
• Addition Polymerization
• Condensation Polymerization

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Addition Polymerization
The entire monomer molecule becomes part of the
polymer

• A polymerization where unsaturated monomers
  combine without rearrangement of their structure
• This is sometimes referred to as vinyl or chain
  polymerization
• This process is essentially a three step process
• The monomer is added to the polymer outright

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Addition- Step 1

• Step 1 is called initialization (I)
• An initiator through the application of thermal
  energy breaks down to form two radicals

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Addition- Step 2

• Step 2 is called growth
• This is where a radical is combined with a
  monomer forming a two unit (mer) molecule
• This radical-monomer is then combined with a
  second monomer adding it in a linear arrangement.
• This continues until it reached the final step

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Addition- Step 3

• Step 3 is called termination
• Chains that are propagating along are terminated
  by either having the two ends of growing chains
  meet and quench the reaction or by having a
  monomer donate a proton to the growing chain
  thereby quenching the reaction

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Addition Examples

• Example 1 Polyethylene (PE)

C8- gasoline C12- oil C18- wax C100- low MW
PE C1000- MDPE C3000- HDPE
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Addition Examples

• Example 2 Polyvinylchloride (PVC)
• Illustrates head-to-tail polymerization
• Clear, toxic monomer
• Degrades need melt point ?? Needs plasticizers
• Plastisol is common combination of LMW PVC WAX,
  DOP
• People hate to mold it

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• Note Head-to-tail addition is favored because
  the one configural form (a) of the adding chain
  is more stable than the other configural form (b)
  of the monomer added to the chain, which is made
  and unmade

(b)
(a)
Examples PE, PP, PS, PVC
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Addition Examples

• Example 3 Polystyrene (PS)
• clear

C2H3C6H5
Polystyrene
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Addition Examples

• Example 4 Teflon (PTFE)
• Never melts because of F-F interaction

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Addition Examples

• Example 5 PAN

• Rayon- Cellulose Acetate Orlon
• Fiber and Films

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Polypropylene Coordination Polymerization

• This is a special type of configurational
  polymerization that results in a molecule being
  added in only one manner
• Specific form of a polymer made
• Ex. PP

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Tacticity

• The way pendant groups are arranged along the
  backbone chain of a polymer
• Heavily pertains to vinyl polymers

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Isotactic

• This is where the side groups are all on the same
  side of the carbon atoms
• Like Cis

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Syndiotactic

• This is where the carbon side groups are on
  alternating sides of the carbon chain
• Desirable
• Like Trans

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Atactic

• This is where there is no regular or repeated
  method to the arrangements on the side groups of
  the carbon chain

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Condensation Polymerization
Part of the monomer molecule (a small molecule)
is kicked out when the monomer becomes part of
the polymer

• Also known as step polymerization
• This is the process where a chemical combination
  of two molecules takes place with the subsequent
  elimination of a small molecule (usually water or
  HCl gas)
• The resulting larger molecule is the combination
  of the other components of the original two
  molecules
• This is essentially a single step process

O
-H2O
Acid (RCOOH) Alcohol (R1- OH)
R-C-O-R1
-H2O
Acid (RCOOH) R NH2 RCOO NH
R1
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Condensation Polymerization

• Two functional groups are needed per molecule
• These groups can be the same or different
• They can be the same for each molecule and the
  number of functional groups on a molecule is
  referred to as its functionality

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Condensation Examples

• Examples
• Acid plus alcohol equals yield as ester plus
  water
• An acid plus an amine gives an amino acid plus
  water

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Condensation Examples

• Nylon- Its a di acid plus a diamine and it
  yields a polyamide

HOOC(CH2)4 COOH H2N (CH2)6 NH2
H2O
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Condensation Examples

• Example 1 Nylon 6,6

Note The nomenclature for nylon is based on the
number of carbon atoms in each of the two
monomers that make up the nylon molecules
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Condensation Examples

• Polyester- this is a diacid plus a dialcohol and
  yielding a polyester

Need
Or from diacids
Terephthalic Acid
H2O
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Condensation Examples

• Polyester
• Note If both R1 and R2 are aliphatic the product
  is too soft
• If both are aromatic the product is too hard
• For PET one is ethyl or butyl and R2 is phenyl
• This results in polyethylene terephthatic

Aromatic possessing thermal stability, a
tendency to undergo electrophilic substitution
rather than addition reactions, and resistance to
oxidation
Aliphatic used to describe non-aromatic
hydrocarbons with no ring structures present
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Condensation Examples

• Polycarbonate- this is carbonic acid and a
  phenolic diol

H2O
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You might say that an addition polymer is like a
good friend who accepts everything about you, the
pleasant and the unpleasant alike.
But a condensation polymer is more like a snotty
social club that says, "Sure you can join, but
only if you ditch those friends of yours".
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Polymerization Comparison

• Addition
• Only growth reaction adds units to the chain

• Condensation
• Any two species can react

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Polymerization Comparison
Condensation 2. Monomer Concentration
Addition2. Monomer concentration
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Polymerization Comparison

• Addition
• 2. Highpolymer formed early

• Condensation
• 2. Molecular weight rises steadily

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Polymerization Comparison

• Addition
• 3. As time increases high conversions but no
  effect on molecular weight

• Condensation
• 3. As time increases it gives higher and higher
  molecular weights

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Polymerization Comparison

• Condensation
• 4. At any time during the reaction there are
  small polymers, as well as intermediate size
  polymers, plus monomers present

• Addition
• 4. At any time there is only monomer,
  highpolymer and a small amount of initiator

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Polymerization Comparison
Condensation 4. Molecular Weight
Addition 4. Molecular Weight
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Where do polymers get their names?

• 1. Their name based on the organic material they
  are derived from
• Ex. Cellulose acetate
• 2. They are named after the monomers that make
  them
• Ex. Ethylene, propylene, and urea
• 3. They are named for their chemical name
• Ex. Polypropylene and polyethylene

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Where do polymers get their names?

• 4. They get their name from a contraction of
  their chemical name
• Ex. Vinyl, acrylic, oelfin
• 5. Names can be based on their initials
• Ex. PS, ABS, PP, and PE
• 6. They get their names from trade names
• Ex. Bakelite, Lexan, Teflon, and Nylon

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Classification of Polymers (Grades)

• Area of application
• Polymer Properties
• Method of fabrication
• Filler and addition type

• Food grade or medical grade
• High heat or High impact
• Extrusion or injection
• Glass filled or mica filled/addition

There are 1000 grades of PE
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Density

• Plastics are bought by weight and sold by volume
• Density Mass/Volume Density D ? (rho)
• OR
• ? M/V therefore M V ?
• Specific Volume
• ? 1/(SV)

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Where do polymer raw materials come from?

• Crude Oil
• Natural Gas