Biodegradable Polymers - Advanced Topic in Polymers Synthesis
Polymers
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Transcript of Polymers
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Polymer IPolymer I
Polymerization, Polymer Polymerization, Polymer Structure, Morphology Structure, Morphology
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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 BlocksPolymer Building Blocks
HydrogenHydrogen Carbon (key)Carbon (key) OxygenOxygen NitrogenNitrogen FluorineFluorine SiliconSilicon SulfurSulfur ChlorineChlorine
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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
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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
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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:
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Addition Polymerization
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Condensation ReactionCondensation Reaction
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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
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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
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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.
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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.
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Levels of Polymer ArchitectureLevels of Polymer Architecture
Monomer TypeMonomer Type
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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
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Polystyrene Polystyrene
PSPS
PolyvinylchloridePolyvinylchloride
PVCPVC
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Levels of Polymer ArchitectureLevels of Polymer Architecture
Monomer TypeMonomer Type Molecule LengthMolecule Length
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Molecular Weight:Molecular Weight:
Number AverageNumber Average
Weight AverageWeight Average
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Levels of Polymer ArchitectureLevels of Polymer Architecture
Monomer TypeMonomer Type Molecule Length – molecular weightMolecule Length – molecular weight Mixture of Monomers - copolymersMixture of Monomers - copolymers
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Types of CopolymersTypes of CopolymersHomopolymer Homopolymer AAAAAAAAAAAAAAAAAAAAAA
RandomRandom CCACBBACABAACCACBBACABAA
AlternatingAlternating ABCABCABCABCABCABCABCABC
Block Block AAAABBBBCCCCAAAABBBBCCCC
GraftGraft
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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
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Isomerism/Polymer TacticityIsomerism/Polymer Tacticity
IsotacticIsotactic
SindiotacticSindiotactic
RandomRandom
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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
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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
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Epoxy Reaction:
Primary Amine
If an Amine is on both ends you get a “crosslink”
Thermoset
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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 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
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AmorphousAmorphous
Example:Example:
PolycarbonatePolycarbonate
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Crystalline
Example: Polyethylene
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CrystalsCrystals
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Chains assume folded
chain conformation
These collect into
lamellar crystallite
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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
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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
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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
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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
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Polymer Categories: NetworkPolymer Categories: Network
ThermosetThermoset vsvs ThermoplasticThermoplastic
NetworkNetwork vsvs LinearLinear
FixedFixed vsvs ReshapeableReshapeable
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Polymer Categories: PricePolymer Categories: Price
CommodityCommodity <$1/pound<$1/pound
EngineeringEngineering $1.5-$5/pound$1.5-$5/pound
SpecialtySpecialty > $5/pound> $5/pound
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Polymer Categories: ApplicationPolymer Categories: Application PlasticsPlastics AdhesivesAdhesives FilmsFilms FibersFibers ElastomersElastomers