8/10/2019 Polymerization Techniques Advantages and Disadvantages

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Polymerization

Process Characteristics Advantages Disadvantages

Bulk Reaction mixture consists

essentially of monomer;

and initiator in the case

of chain reaction

polymerizationMonomer acts as solvent

for polymers

Products relatively pure due to

minimum contamination

Enhanced yield per reactor volume

Exothermic nature of polymerization

reactions (particularly chain reaction

polymerizations) makes temperature

control of system difficult

Product has broad molecular weightdistribution

Removals of tracers of unreacted

monomer difficult

Solution Solvent miscible with

monomer, dissolves

polymer

Heat transfer efficiency greatly

enhanced resulting in better process

control

Resulting polymer solution may be

directly usable

Necessary to select an inert solvent to

avoid possible transfer to solvent

Lower yield per rector volume

Reduction of reaction rate and average

chain length

Not particularly suitable for production

of dry or relatively pure polymer due

to difficulty of complete solvent

removal

Suspension Monomer and polymer

insoluble in water,

initiator soluble inmonomer

Heat removal and temperature control

relatively easier

Polymer obtained in a form that isconvenient and easily handled

Resulting polymer suspension or

granules may be directly usable

Need to maintain stability of droplets

requires continuous and a minimum

level of agitationPossibility of polymer contamination

by absorption of stabilizer on particle

surface

Continuous operation of system

difficult

Emulsion Monomer and polymer

insoluble in water,

initiator soluble in waterEmulsifier needed for

stabilization of system

component particularly

at initial stages of

polymerization

Physical state of the system enhances

heat transfer efficiency

Possible to obtain high rates ofpolymerization and high average

chain lengths

Narrow molecular weight distribution

Latex (emulsion) often directly usable

Difficult to get pure polymer due to

contamination from other

components of polymerizationsystem

Difficult and expensive if solid

polymer product is required

Presence of water lowers yield per

reactor volume

Precipitation Polymer insoluble in

monomer or monomer

miscible with precipitant

for polymer

Physical state of system permits easy

agitation

Relatively low temperatures

employed

Separation of product difficult and

expensive

Catalyst systems are special and need

careful preparation

Molecular weight distribution depends

on type of catalyst

Interfacial Polymerization occurs at

interface of two

immiscible solvents,

usually water and anorganic solvent

Polymerization is rapid and occurs at

low temperatures

High conversions are not necessarily

required to obtain high molecularweight

Unnecessary to start with

stoichiometric quantifiers of

reactants

Limited to highly reactive systems

Need appropriate choice of solvent to

dissolve reactants