1. PE335: Polymerization Techniques

2. Production Steps End Product Monomer Co-monomer(s)
Type of polymerization
Co-catalysts
Donors etc.
Initiator/Catalyst
Technique/Reactor
Reaction conditions
Polymer resin
Compounding/Processing
Techniques
End Product

3. Polymerization Techniques
1. Homogeneous systems
1.1. Bulk polymerization
1.2. Solution polymerization
2. Heterogeneous systems
2.1. Suspension polymerization
2.2. Emulsion polymerization
2.3. Precipitation polymerization
2.4. Polymerization in solid state
2.5. Polymerization in the gas phase
Techniques

4. Advantages and Limitations
Techniques

5. Choice of Polymerization Technique
Sometimes for one monomer several techniques of polymerizing are available. Choice of a specific technique depends on certain factors:
Kinetic / mechanistic factors related to chain length, chain composition
Technological factors e.g. heat removal, reaction rate, viscosity of the reaction mixture, morphology of the product
Economic factors; production costs, environmental aspects, purification steps etc.
Techniques

6. Bulk Polymerization Neat monomer (and initiator)
Simplest formulation and equipment
Most difficult in control, when polymerization is very exothermic
Common problems: (1) heat transfer (2) increase in viscosity
If polymer is insoluble in monomer  polymer precipitate
(1) viscosity would remain similar
(2) occlusion of radicals (within the polymer droplet) is unavoidable
Radical occlusion  autoacceleration  crosslinked polymer nodules
(i.e. popcorn polymerization)
The crosslinked nodules (light weight and large volume) may cause
fouling or fracture of the polymerization apparatus
Commercial uses
Casting formulations
Low MW polymers for adhesives, plasticizers, tackifiers,
and lubricant additives
Techniques

7. Suspension polymerization
Disperse monomer droplets in a noncompatible liquid (e.g. H2O)
Polymerize the monomer by an initiator (soluble in the monomer)
Stabilize the dispersion with a stabilizer (e.g. poly(vinyl alcohol) or methyl cellulose)
Isolate granular bead products by filtration or spray drying
Heat transfer is efficient and reaction is easily controlled
Similar to bulk polymerization in kinetics and mechanism
Commercial uses
For making granular polymers, e.g. PS, PVC, PMMA
Techniques

8. Solution Polymerization
Use monomer solution
Heat transfer is very efficient
MW may be severely limited by chain transfer reaction
(probably caused by the solvent molecule or its impurities)
Solvent residues  difficult to remove completely
Environmental concerns  organic solvent waste
Use supercritical CO2 as a polymerization solvent 
nontoxic, inexpensive, easily removed and recycled
Techniques

9. Solution Polymerization
Techniques

10. Emulsion polymerization
Emulsification
Add emulsifying agent (e.g., soap or detergent) in an aqueous solution
 to form micelles
Monomers enter and swell the micelles
Initiation
Radicals (redox type) are generated in the aqueous phase and diffuse
into micelles
Propagation
Polymerization propagated within micelles
More monomers enter micelles to support the polymerization
Termination
Termination by radical combination when a new radical enters the
micelle
Results
Extremely high MW are obtainable, but often too high to be useful
Chain transfer reagents are often added to control the MW
Also suitable for tacky polymers (∵ small particles are relative stable and
can resist agglomeration)
Techniques

11. Techniques

12. Stages of Particle Growth
Three different stages
Nucleation of particles
Particle growth in presence of
monomer droplets
(3) Particle growth in absence of
(Thoenes, 1991)
Techniques

13. Emulsion Polymerization Recipe
Water (continuous phase)
Water-insoluble monomer
Water-soluble initiator
Surfactant
Techniques 13

14. Emulsion Polymerization Recipe
Techniques 14

15. Techniques

16. Techniques

17. Gas Phase Polymerization: Light olefins
Fluidized bed polymerization
Techniques

18. Hybrid Reactor for Polypropylene
The process is a mass polymerization of propylene:
A catalytic system is prepared and made to react in a controlled manner with a small amount of liquid propylene, inside a small- capacity reactor (prepolymer)
2) The product of the pre-polymer is taken to the Loop tubular reactors (pressure of 32 bars and 70°C) for further polymerization .
3) Separation of the non-reacted monomer from the solid polymer by gasification of the (un-reacted) liquid propylene.
4) The polypropylene is washed with water vapor to eliminate any still- active catalyst, then dried with hot nitrogen.
5) PP is compounded according to the requirements of its specific application.
Techniques

19. End
Techniques