Industrial Techniques of Polymerization Flashcards
Polymerization technique may be divided into two primary categories
homogenous
heterogenous
occurs within a single phase and is further subdivided into bulk
polymerization and solution polymerization
homogenous
involves reactions occurring across two or more phases.
heterogenous
A type of polymerization process that occurs in a single uniform phase is called
homogenous polymerization
Two types of homogenous polymerization
Bulk
Solution
e simplest technique and gives
a high purity of polymer.
bulk polymerization
only requires monomer, initiator, and chain
transfer agent, this chain transfer agent is used to
control the molecular weight.
bulk polymerization
In bulk polymerization, the monomer is in _______ and and the initiator, and the chain
transfer agent is ___________
liquid phase, dissolved
Bulk polymerization reaction is mildly
exothermic
Advantages of bulk polymerization
high yield per reactor volume,
easy polymer recovery,
the ability to cast the polymerization mixture
Limitations of bulk polymerization
challenge of removing the last trace of monomer
managing the heat generated during the polymerization process
The rate of polymerization of a liquid monomer may be
followed by monitoring the
change in volume by dilatometry or the increase in viscosity
This means that the macroradicals concentration will
increase and therefore the termination rate will decrease, and the overall rate of polymerization
increases with the accompanying additional heat production,
autoacceleration/Norris-Trommsdorff/gel effect
Explain Norris Trommsdorff
At high
viscosity, the diffusion of long chain radical required for termination is hindered because the
macroradicals are unable to diffuse readily in the viscous medium. In contrast, at low viscosity the
monomers may diffuse readily and high molecular weight macroradicals are produced as the result
of propagation in the absence of termination.
Example of bulk polymerization
Vinyl monomer polymerization
The heat problem in bulk
polymerization can be solved using
solution polymerization due to the use of solvent or water
Polymerization is under the
condition of ____________to
maximize heat removal
solvent reflux
The ________________
must be soluble in the solvent and
the solvent has low chain-transfer
constant and suitable melting and boiling point for solution polymerization
initiator and monomer
polymerized in the presence of an initiator in a benzene solution to create
poly(vinyl acetate) (PVAc
Vinyl acetate
continues to increase until the reaction
is complete, but the concentration of the solution is usually diluted to exhibit autoacceleration
because of the gel effect
viscosity of the solution
polymerization that involves two or more phases either
during or after the polymerization process.
Heterogenous polymerizations
Examples of heterogenous polymerizations
(Gas)
Emulsion
Inverse emulsion
Redox initiation
(Liquid)
Suspension
Precipitation
Solid Phase
Emerging techniques
Gas phase
Plasma polymerization
group transfer polymerization
Examples of hydrocarbon plastics and elastomers
Polyethylene
Polypropelene
Natural Rubber
Olefine based polymers
Synthetic
Carbon-chain polymers
Polystyrene
Acrylic
Poly(vinyl) esters
Chlorine containing
Fluorine
Heterochain thermoplastics
Polyamides and polypeptides
Polyesters, polyethers, related polymers
cellulosic polymers
high temperature and inorganic polymers
