Polymerization in a Batch Reactor

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This Demonstration shows the number fraction (blue) and weight fraction
(green) of polymer chains as functions of the number of monomer units for polymerization in a batch reactor. Select "step-growth" or "free-radical" polymerization with buttons, and use sliders to set reaction rate constants, initial concentrations and reaction time. The number average chain length
and the polydispersity are shown. Distributions are calculated using the Flory–Schulz model. The
and
axes ranges change as the parameters change, and the thick red tick marks on the purple axes show the plot ranges used.
Contributed by: Rachael L. Baumann and Nathan S. Nelson (February 2016)
Additional contributions by: John L. Falconer and Nick Bongiardina
(University of Colorado Boulder, Department of Chemical and Biological Engineering)
Open content licensed under CC BY-NC-SA
Snapshots
Details
The number fraction and weight fraction
of polymer chains for a polymer with
monomer units are:
,
,
where is mole fraction and
is the fraction of functional groups that have reacted:
.
For step-growth polymerization:
,
.
For free-radical polymerization:
,
,
where and
are the initial monomer and initiator concentrations;
is monomer concentration;
,
and
are the rate constants for the reaction, initiation and termination;
is time;
is the terminator concentration and
is fraction of chains initiated by initiator.
The number and weight
average chain lengths are:
,
,
where is the polymer concentration.
The polydispersity is:
.
Reference
[1] H. S. Fogler, Elements of Chemical Reaction Engineering, 5th ed., Boston: Prentice Hall, 2016.
Permanent Citation