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
