Polymer IPolymer I

Polymerization, Polymer Polymerization, Polymer Structure, Morphology Structure, Morphology

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.

Polymer Building BlocksPolymer Building Blocks

HydrogenHydrogen Carbon (key)Carbon (key) OxygenOxygen NitrogenNitrogen FluorineFluorine SiliconSilicon SulfurSulfur ChlorineChlorine

Carbon Is KeyCarbon Is Key

Atomic number: 6Atomic number: 6

Valence: 2sValence: 2s222p2p2 2

Hybrid orbital- sp Hybrid orbital- sp

Will share up to Will share up to fourfour electrons, tetrahedral electrons, tetrahedral arrangementarrangement

Polymerization ProcessesPolymerization Processes

Addition PolymerizationAddition Polymerization• No ByproductsNo Byproducts• Usually heat drivenUsually heat driven

Condensation PolymerizationCondensation Polymerization• Byproducts producedByproducts produced• Removal of byproduct controls rateRemoval of byproduct controls rate

Linear AdditionLinear Addition

Begin with ethylene (gas)Begin with ethylene (gas)

Monomer or “mer”Monomer or “mer”

Each bond is a shared Each bond is a shared

electron pair.electron pair.

A polymer is formed by A polymer is formed by catalyzing the formation of catalyzing the formation of a free radical:a free radical:

Addition Polymerization

Condensation ReactionCondensation Reaction

Effects of Polymerization SchemeEffects of Polymerization Scheme

Polymer may contain residual Polymer may contain residual byproduct.byproduct.

Addition polymerization done in Addition polymerization done in solvent may have residual solventsolvent may have residual solvent

Cleanest polymers are gas phase or Cleanest polymers are gas phase or aqueous solution polymersaqueous solution polymers

Basic Steps in PolymerizationBasic Steps in Polymerization

Initiation: Initiation: Formation of Formation of free radicalfree radical

Propagation: Propagation: Combining of Combining of mers to form mers to form chainschains

Termination: Termination: Elimination of Elimination of free radicalsfree radicals

Polymerization Step EffectsPolymerization Step Effects

The actual method of initiation, The actual method of initiation, propagation, termination will affect propagation, termination will affect final properties.final properties.

You cannot easily switch suppliers or You cannot easily switch suppliers or resin once a particular material and resin once a particular material and factory have been qualified.factory have been qualified.

Properties Properties

Behavior determined by a Behavior determined by a combination of primary backbone combination of primary backbone bonds and secondary bonds.bonds and secondary bonds.

Different monomers will have Different monomers will have different secondary bond strengths. different secondary bond strengths.

Levels of Polymer ArchitectureLevels of Polymer Architecture

Monomer TypeMonomer Type

Families based on an ethenic backbone are Families based on an ethenic backbone are vinylvinyl polymers or vinylydines polymers or vinylydines

Polyethylene Polyethylene

PEPE

PolypropylenePolypropylene

PPPP

Polystyrene Polystyrene

PSPS

PolyvinylchloridePolyvinylchloride

PVCPVC

Levels of Polymer ArchitectureLevels of Polymer Architecture

Monomer TypeMonomer Type Molecule LengthMolecule Length

Molecular Weight:Molecular Weight:

Number AverageNumber Average

Weight AverageWeight Average

Levels of Polymer ArchitectureLevels of Polymer Architecture

Monomer TypeMonomer Type Molecule Length – molecular weightMolecule Length – molecular weight Mixture of Monomers - copolymersMixture of Monomers - copolymers

Types of CopolymersTypes of CopolymersHomopolymer Homopolymer AAAAAAAAAAAAAAAAAAAAAA

RandomRandom CCACBBACABAACCACBBACABAA

AlternatingAlternating ABCABCABCABCABCABCABCABC

Block Block AAAABBBBCCCCAAAABBBBCCCC

GraftGraft

Levels of Polymer ArchitectureLevels of Polymer Architecture

Monomer TypeMonomer Type Molecule Length – molecular weightMolecule Length – molecular weight Mixture of Monomers – copolymersMixture of Monomers – copolymers Monomer Arrangement - IsomersMonomer Arrangement - Isomers

Isomerism/Polymer TacticityIsomerism/Polymer Tacticity

IsotacticIsotactic

SindiotacticSindiotactic

RandomRandom

Levels of Polymer ArchitectureLevels of Polymer Architecture

Monomer TypeMonomer Type Molecule Length – molecular weightMolecule Length – molecular weight Mixture of Monomers – copolymersMixture of Monomers – copolymers Monomer Arrangement – IsomersMonomer Arrangement – Isomers Bond/Network StructureBond/Network Structure

Polymer CategoriesThermoplastic – 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

Epoxy Reaction:

Primary Amine

If an Amine is on both ends you get a “crosslink”

Thermoset

Thermoset

Frequent Cross-links Create 3-D Network

Amorphous Polymer – Lightly Crosslinked

Semicrystalline Thermoplastic

Levels of Polymer ArchitectureLevels of Polymer Architecture

Monomer TypeMonomer Type Molecule Length – molecular weightMolecule Length – molecular weight Mixture of Monomers – copolymersMixture of Monomers – copolymers Monomer Arrangement – IsomersMonomer Arrangement – Isomers Bond/Network StructureBond/Network Structure Molecular Conformation Molecular Conformation

AmorphousAmorphous

Example:Example:

PolycarbonatePolycarbonate

Crystalline

Example: Polyethylene

CrystalsCrystals

Chains assume folded

chain conformation

These collect into

lamellar crystallite

Two crystalline morphologiesTwo crystalline morphologies

(collections of lamellar crystalites)(collections of lamellar crystalites)

Spherulite (no shear)Spherulite (no shear)

Row Nucleated (shear )Row Nucleated (shear )

Shish-kebabShish-kebab

Levels of Polymer ArchitectureLevels of Polymer Architecture

Monomer TypeMonomer Type Molecule Length – molecular weightMolecule Length – molecular weight Mixture of Monomers – copolymersMixture of Monomers – copolymers Monomer Arrangement – IsomersMonomer Arrangement – Isomers Bond/Network StructureBond/Network Structure Molecular Conformation Molecular Conformation Blends/AlloysBlends/Alloys

Polymer BlendsPolymer Blends

Mixture of Mixture of compatible compatible polymerspolymers

No primary bondsNo primary bonds Intermediate Intermediate

propertiesproperties May be phase May be phase

separation separation

Levels of Polymer ArchitectureLevels of Polymer Architecture

Monomer TypeMonomer Type Molecule Length – molecular weightMolecule Length – molecular weight Mixture of Monomers – copolymersMixture of Monomers – copolymers Monomer Arrangement – IsomersMonomer Arrangement – Isomers Bond/Network StructureBond/Network Structure Molecular Conformation Molecular Conformation Blends/AlloysBlends/Alloys AdditivesAdditives

Polymer Categories: NetworkPolymer Categories: Network

ThermosetThermoset vsvs ThermoplasticThermoplastic

NetworkNetwork vsvs LinearLinear

FixedFixed vsvs ReshapeableReshapeable

Polymer Categories: PricePolymer Categories: Price

CommodityCommodity <$1/pound<$1/pound

EngineeringEngineering $1.5-$5/pound$1.5-$5/pound

SpecialtySpecialty > $5/pound> $5/pound

Polymer Categories: ApplicationPolymer Categories: Application PlasticsPlastics AdhesivesAdhesives FilmsFilms FibersFibers ElastomersElastomers