Transcript Polymer I Polymerization, Polymer Structure, Morphology

Polymer I
Polymerization, Polymer
Structure, Morphology
Objectives
1. Explain the basic steps in polymerization.
Objectives
1. Explain the basic steps in polymerization.
2. Explain the epoxy/amine reaction mechanism.
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.
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.
Objectives
1.
2.
3.
4.
Explain the basic steps in polymerization.
Explain the epoxy/amine reaction mechanism.
Sketch/identify the four basic vinyl molecules
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.
Polymer Building Blocks
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Hydrogen
Carbon (key)
Oxygen
Nitrogen
Fluorine
Silicon
Sulfur
Chlorine
Carbon Is Key
Atomic number: 6
Valence: 2s22p2
Hybrid orbital- sp
Will share up to four
electrons, tetrahedral
arrangement
Polymerization Processes
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Addition Polymerization
• No Byproducts
• Usually heat driven
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Condensation Polymerization
• Byproducts produced
• Removal of byproduct controls rate
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:
Addition Polymerization
Condensation Reaction
Effects of Polymerization Scheme
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Polymer may contain residual
byproduct.
Addition polymerization done in
solvent may have residual solvent
Cleanest polymers are gas phase or
aqueous solution polymers
Basic Steps in Polymerization
Initiation:
Formation of
free radical
Propagation:
Combining of
mers to form
chains
Termination:
Elimination of
free radicals
Polymerization Step Effects
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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.
Properties
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Behavior determined by a
combination of primary backbone
bonds and secondary bonds.
Different monomers will have
different secondary bond strengths.
Levels of Polymer Architecture
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Monomer Type
Families based on an ethenic backbone are
vinyl polymers or vinylydines
Polyethylene
PE
Polypropylene
PP
Polystyrene
PS
Polyvinylchloride
PVC
Levels of Polymer Architecture
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Monomer Type
Molecule Length
Molecular Weight:
Number Average
Weight Average
Levels of Polymer Architecture
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Monomer Type
Molecule Length – molecular weight
Mixture of Monomers - copolymers
Types of Copolymers
Homopolymer
Random
Alternating
Block
Graft
AAAAAAAAAAA
CCACBBACABAA
ABCABCABCABC
AAAABBBBCCCC
Levels of Polymer Architecture
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Monomer Type
Molecule Length – molecular weight
Mixture of Monomers – copolymers
Monomer Arrangement - Isomers
Isomerism/Polymer Tacticity
Isotactic
Sindiotactic
Random
Levels of Polymer Architecture
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Monomer Type
Molecule Length – molecular weight
Mixture of Monomers – copolymers
Monomer Arrangement – Isomers
Bond/Network Structure
Polymer Categories
Thermoplastic – only secondary bonds between
molecules.
-”Plastic” or reshapable
- Melted and formed under pressure
- Higher tooling costs
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
Thermoset
Epoxy Reaction:
Primary Amine
If an Amine is on
both ends you get a
“crosslink”
Polyester Reaction
Thermoset
Frequent Cross-links Create 3-D Network
Amorphous Polymer – Lightly Crosslinked
Semicrystalline Thermoplastic
Levels of Polymer Architecture
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Monomer Type
Molecule Length – molecular weight
Mixture of Monomers – copolymers
Monomer Arrangement – Isomers
Bond/Network Structure
Molecular Conformation
Amorphous
Example:
Polycarbonate
Crystalline
Example: Polyethylene
Crystals
Chains assume folded
chain conformation
These collect into
lamellar crystallite
Two crystalline morphologies
(collections of lamellar crystalites)
Spherulite (no shear)
Row Nucleated (shear )
Shish-kebab
Levels of Polymer Architecture
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Monomer Type
Molecule Length – molecular weight
Mixture of Monomers – copolymers
Monomer Arrangement – Isomers
Bond/Network Structure
Molecular Conformation
Blends/Alloys
Polymer Blends
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Mixture of
compatible
polymers
No primary bonds
Intermediate
properties
May be phase
separation
Levels of Polymer Architecture
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Monomer Type
Molecule Length – molecular weight
Mixture of Monomers – copolymers
Monomer Arrangement – Isomers
Bond/Network Structure
Molecular Conformation
Blends/Alloys
Additives
Polymer Categories: Network
Thermoset
vs
Thermoplastic
Network
vs
Linear
Fixed
vs
Reshapeable
Polymer Categories: Price
Commodity
<$1/pound
Engineering
$1.5-$5/pound
Specialty
> $5/pound
Polymer Categories: Application
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Plastics
Adhesives
Films
Fibers
Elastomers
Self-Test
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Draw the monomer structure of
polyethylene.
What crystalline morphology forms
under shear?
Which type of polymer cannot be
reshaped by heat and pressure?