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Polymer IPolymerization, 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, tetrahedralarrangement

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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 sharedelectron pair.

A polymer is formed bycatalyzing 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 residualbyproduct.

Addition polymerization done insolvent may have residual solvent

Cleanest polymers are gas phase oraqueous solution polymers

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Basic Steps in Polymerization

Initiation: Formation of free radical

Propagation: Combining of mers to formchains

Termination: Elimination of free radicals

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Polymerization Step Effects

The actual method of initiation,propagation, termination will affectfinal properties.

You cannot easily switch suppliers orresin once a particular material andfactory have been qualified.

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Properties

Behavior determined by acombination of primary backbonebonds and secondary bonds.

Different monomers will havedifferent secondary bond strengths.

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Levels of Polymer Architecture

Monomer Type

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Families based on an ethenic backbone arevinyl polymers or vinylydines

Polyethylene

PE

PolypropylenePP

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PolystyrenePS

PolyvinylchloridePVC

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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 CopolymersHomopolymer AAAAAAAAAAA

Random CCACBBACABAA

Alternating ABCABCABCABCBlock 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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Epoxy Reaction:

Primary Amine

If an Amine is on

both ends you get a“crosslink” 

Thermoset

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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

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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 compatiblepolymers

No primary bonds Intermediate

properties

May be phaseseparation

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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 <$1/pound

Engineering $1.5-$5/pound

Specialty > $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 formsunder shear?

Which type of polymer cannot bereshaped by heat and pressure?