polymers
TRANSCRIPT
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