This document discusses various types of industrial polymerization processes, including: 1) Homogeneous processes like bulk/mass and solution polymerization that involve miscible reactants and polymers. 2) Heterogeneous processes like suspension, emulsion, and precipitation polymerization that use immiscible systems. Suspension polymerization disperses monomer droplets in a stability medium while emulsion polymerization uses an emulsifying agent to suspend components in water. 3) Interfacial/solution polycondensation processes that use separate aqueous and organic phases or a solvent for polymerization. The document provides examples of specific polymers produced by different processes and notes challenges like removing solvents.

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ICH404: Polymer Technology
Prepared by Dr. Lukman B. Abdulra’uf
Large scale industrial polymerisation processes; mechanical properties of polymers; introduction to polymer
rheology, polymer processing – injection, extrusion, calendaring, compression and transfer; moulding of
thermoplastics; important methods of processing thermosets; polymer morphology
1. Ebewele, R. O. (1996). Polymer science and technology. Boca Raton: CRC Press pp258
2. Goodwin, J. W. and Hughes, R. W. (2012). Rheology for Chemists. Cambridge: RSC Publishing
3. Guo, Q (ed). Polymer morphology: principles, characterization and processing. New Jersey: John Wiley
& Sons
Large Scale Industrial Polymerization Processes
Polymerization processes may be classified in
i. Homogeneous: it is a polymerization process in which all reactants (monomers, initiators and solvents)
are mutually soluble and compatible with the resulting polymer
ii. Heterogeneous: is a polymerization process in which all the reactant (monomers, catalysts, and the
polymer) are mutually immiscible.
Types of Homogeneous Polymerization Processes
a. Bulk/Mass Polymerization: in this process, the reaction mixture consists essentially of the monomers, a
soluble initiator (chain growth polymerization) and modifiers. The product polymer and all the starting
materials are miscible. As the reaction proceeds, mixing and heat transfer become difficult due to increase
in viscosity of the reaction medium. The temperature of polymerization depends on the polymerization
system.
Bulk polymerization is suited for making pure polymeric products, such as optical grade poly(methyl
methacrylate) or impact-resistant polystyrene, because of minimal contamination of the product.
However, removal of the unreacted monomer is usually necessary, and this can be a difficult process.
b. Solution Polymerization: in this process, the monomer, initiator and resulting polymer are all soluble in
the solvent. It involves stirring together of the monomer, catalyst and solvent to form a solution that reacts
without heating or cooling. But, elaborate equipment may be required and polymerization process is
performed in solution continuously or batchwise
Solution polymerization is used widely in ionic and coordination polymerization for the production of
high-density polyethylene, polybutadiene, and butyl rubber.
The drawbacks of solution polymerization is that, the solubility of polymers is generally limited,
particularly at higher molecular weights and the problem of cleaning equipment and disposal of dirty
solvent constitutes another disadvantage of solution polymerization.
Types of Heterogeneous Polymerization Processes
a. Suspension Polymerization: it involves the dispersion of the monomer, mainly as a liquid in small
droplets, into an agitated stability medium, consisting of water contains small amount of suspension
agents. The catalyst or initiator is dissolved in the monomer if the monomer is a liquid or included in the
reaction medium if a gaseous monomer is used. When polymerization is completed, the polymer
suspension is sent to a blowdown tank to remove the remaining monomer.
Styrene, methyl methacrylate, vinyl chloride, vinylidene chloride, vinyl acetate, the fluorocarbons, and
some gaseous monomers, including ethylene, propylene and formaldehyde, may be polymerized by the
suspension polymerization process.

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As the reactor size increases, problems are generally encountered with heat transfer surfaces. Even
when dimensional similarity is maintained, heat transfer area does not increase in direct proportion to
the reactor volume.
b. Emulsion Polymerization: In emulsion polymerization system, the following starting materials are
needed: monomer(s), dispersing medium, emulsifying agent, water-soluble initiator, and, possibly, a
transfer agent. Water serves as the dispersing medium in which the various components are suspended by
the emulsifying agent, The water also acts as a heat transfer medium
All polymers made by this process are addition that require free-radical initiators. Monomers such as
styrene, acrylates, methacrylates, vinyl chloride, butadiene, and chloroprene are used in emulsion
polymerization.
The disadvantage include: surfactants and other polymerization adjuvants remain in the polymer and are
difficult to remove.
c. Precipitation Polymerization: is also known slurry polymerization, involves solution systems in which
the monomer is soluble but the polymer is not. The process involves, essentially, a catalyst preparation
step and polymerization at pressures usually less than 50 atm and low temperatures (less than 100 ℃).
The resultant polymer, which is precipitated as fine flocs, forms a slurry consisting of about 20% polymer
suspended in solvent.
It is probably the most important process for the coordination polymerization of olefins.
Problems may arise due to settling of the polymer and the formation of deposits on the stirrer and reactor
walls.
d. Interfacial/Solution Polycondensations: It involves a pair of immiscible liquids (water and
hydrocarbons such as hexane, xylene, or carbon tetrachloride). The aqueous phase contains the diamine,
diol, or other active hydrogen compound and the acid receptor or base (e.g., NaOH). The organic phase
contains the acid chloride, and polymerization occurs interfacially between the two liquids. In solution
polycondensation, all the reactants are dissolved in a simple, inert solvent. However, for some solution
polymerizations, the solvent can facilitate the reaction.
Interfacial and solution polycondensations are utilized in the production of polyamide fibers. It is also
used in enhancement of shrink resistance of wool
The main disadvantage is that large amount of solvents are used.