Documents
Resources
Learning Center
Upload
Plans & pricing Sign in
Sign Out
Your Federal Quarterly Tax Payments are due April 15th Get Help Now >>

Polymers I-2

VIEWS: 314 PAGES: 38

									    Polymers
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. 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 Blocks
       Hydrogen
       Carbon (key)
       Oxygen
       Nitrogen
       Fluorine
       Silicon
       Sulfur
       Chlorine
      Polymerization Processes
   Addition Polymerization
    • No Byproducts
    • Usually heat driven


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

   Different monomers will have
    different secondary bond strengths.
    Levels of Polymer Architecture
   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
   Monomer Type
   Molecule Length
Molecular Weight:

 Number Average




Weight Average
    Levels of Polymer Architecture
   Monomer Type
   Molecule Length – molecular weight
   Mixture of Monomers - copolymers
    Types of Copolymers
Homopolymer   AAAAAAAAAAA
Random        CCACBBACABAA
Alternating   ABCABCABCABC
Block         AAAABBBBCCCC
Graft
    Levels of Polymer Architecture
   Monomer Type
   Molecule Length – molecular weight
   Mixture of Monomers – copolymers
   Monomer Arrangement - Isomers
Isomerism/Polymer Tacticity

Isotactic



Sindiotactic



Random
    Levels of Polymer Architecture
   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




Frequent Cross-links Create 3-D Network
Amorphous Polymer – Lightly Crosslinked
Semicrystalline Thermoplastic
    Levels of Polymer Architecture
   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
    Levels of Polymer Architecture
   Monomer Type
   Molecule Length – molecular weight
   Mixture of Monomers – copolymers
   Monomer Arrangement – Isomers
   Bond/Network Structure
   Molecular Conformation
   Blends/Alloys
    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
Polymer Categories: Network

Thermoset   vs   Thermoplastic

Network     vs       Linear

Fixed       vs   Reshapeable
Polymer Categories: Application
          Plastics
          Adhesives
          Films
          Fibers
          Elastomers

								
To top