Polymer I

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Polymer I

• Polymerization, Polymer Structure, Morphology

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Objectives

1. Explain the basic steps in polymerization.

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Objectives

1. Explain the basic steps in polymerization.
2. Explain the epoxy/amine reaction mechanism.

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Objectives

1. Explain the basic steps in polymerization.
2. Explain the epoxy/amine reaction mechanism.
3. Identify the grafting/copolymer structures and/or
   name them.

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Objectives

1. Explain the basic steps in polymerization.
2. Explain the epoxy/amine reaction mechanism.
3. Identify the grafting/copolymer structures and/or
   name them.
4. Identify or sketch the various isomeric
   structures possible with a vinyl polymer.

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Objectives

1. Explain the basic steps in polymerization.
2. Explain the epoxy/amine reaction mechanism.
3. Sketch/identify the four basic vinyl molecules
4. Identify the grafting/copolymer structures and/or
   name them.
5. Identify or sketch the various isomeric
   structures possible with a vinyl polymer.
6. Explain the basis for polymer crystallinity.

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Polymer Building Blocks

• Hydrogen
• Carbon (key)
• Oxygen
• Nitrogen
• Fluorine
• Silicon
• Sulfur
• Chlorine

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Carbon Is Key

• Atomic number 6
• Valence 2s22p2
• Hybrid orbital- sp
• Will share up to four electrons, tetrahedral
  arrangement

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Polymerization Processes

• Addition Polymerization
• No Byproducts
• Usually heat driven
• Condensation Polymerization
• Byproducts produced
• Removal of byproduct controls rate

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• Linear Addition
• Begin with ethylene (gas)
• Monomer or mer
• Each bond is a shared
• electron pair.
• A polymer is formed by catalyzing the formation
  of a free radical

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Addition Polymerization
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Condensation Reaction
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Effects of Polymerization Scheme

• Polymer may contain residual byproduct.
• Addition polymerization done in solvent may have
  residual solvent
• Cleanest polymers are gas phase or aqueous
  solution polymers

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• Basic Steps in Polymerization
• Initiation Formation of free radical
• Propagation Combining of mers to form
  chains
• Termination Elimination of free radicals

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Polymerization Step Effects

• The actual method of initiation, propagation,
  termination will affect final properties.
• You cannot easily switch suppliers or resin once
  a particular material and factory have been
  qualified.

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Properties

• Behavior determined by a combination of primary
  backbone bonds and secondary bonds.
• Different monomers will have different secondary
  bond strengths.

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Levels of Polymer Architecture

• Monomer Type

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• Families based on an ethenic backbone are vinyl
  polymers or vinylydines
• Polyethylene
• PE
• Polypropylene
• PP

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• Polystyrene
• PS
• Polyvinylchloride
• PVC

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Levels of Polymer Architecture

• Monomer Type
• Molecule Length

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• Molecular Weight
• Number Average
• Weight Average

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Levels of Polymer Architecture

• Monomer Type
• Molecule Length molecular weight
• Mixture of Monomers - copolymers

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Types of Copolymers

• Homopolymer AAAAAAAAAAA
• Random CCACBBACABAA
• Alternating ABCABCABCABC
• Block AAAABBBBCCCC
• Graft

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Levels of Polymer Architecture

• Monomer Type
• Molecule Length molecular weight
• Mixture of Monomers copolymers
• Monomer Arrangement - Isomers

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• Isomerism/Polymer Tacticity
• Isotactic
• Sindiotactic
• Random

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Levels of Polymer Architecture

• Monomer Type
• Molecule Length molecular weight
• Mixture of Monomers copolymers
• Monomer Arrangement Isomers
• Bond/Network Structure

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Polymer Categories Thermoplastic only secondary
bonds between molecules. -Plastic or
reshapable - Melted and formed under
pressure - Higher tooling costs
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• Polymer Categories
• Thermoplastic only secondary bonds between
  molecules.
• -Plastic or reshapable
• - Melted and formed under pressure
• - Higher tooling costs
• Thermoset primary and secondary bonds between
  molecule segments.
• - Cannot be reshaped
• - Low viscosity in processing
• - Cheaper tooling

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Thermoset
Epoxy Reaction Primary Amine If an Amine is on
both ends you get a crosslink
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Polyester Reaction
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Thermoset
Frequent Cross-links Create 3-D Network
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Amorphous Polymer Lightly Crosslinked
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Semicrystalline Thermoplastic
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Levels of Polymer Architecture

• Monomer Type
• Molecule Length molecular weight
• Mixture of Monomers copolymers
• Monomer Arrangement Isomers
• Bond/Network Structure
• Molecular Conformation

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• Amorphous
• Example
• Polycarbonate

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Crystalline
Example Polyethylene
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• Crystals

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Chains assume folded chain conformation
These collect into lamellar crystallite
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• Two crystalline morphologies
• (collections of lamellar crystalites)
• Spherulite (no shear)
• Row Nucleated (shear )
• Shish-kebab

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Levels of Polymer Architecture

• Monomer Type
• Molecule Length molecular weight
• Mixture of Monomers copolymers
• Monomer Arrangement Isomers
• Bond/Network Structure
• Molecular Conformation
• Blends/Alloys

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Polymer Blends

• Mixture of compatible polymers
• No primary bonds
• Intermediate properties
• May be phase separation

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Levels of Polymer Architecture

• Monomer Type
• Molecule Length molecular weight
• Mixture of Monomers copolymers
• Monomer Arrangement Isomers
• Bond/Network Structure
• Molecular Conformation
• Blends/Alloys
• Additives

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Polymer Categories Network

• Thermoset vs Thermoplastic
• Network vs Linear
• Fixed vs Reshapeable

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Polymer Categories Price

• Commodity lt1/pound
• Engineering 1.5-5/pound
• Specialty gt 5/pound

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Polymer Categories Application

• Plastics
• Adhesives
• Films
• Fibers
• Elastomers

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Self-Test

• Draw the monomer structure of polyethylene.
• What crystalline morphology forms under shear?
• Which type of polymer cannot be reshaped by heat
  and pressure?