LearnChemE

Polymerization Reactors: Summary

The answers to the ConcepTests are given below and will open in a separate window. 
Key points from this module:
  1. The type of reactor has a large influence on the molecular weight distribution (MWD) for a polymer.
  2. The MWD is affected by the residence time distribution of the reactor, the concentration at which reaction takes place, and the chain growth time of the polymerization.
  3. For condensation polymerization, the chain growth time can be greater than the mean residence time.
  4. When the chain growth time > mean residence time, a PFR or batch reactor will have a narrower MWD than a CSTR because all molecules have the same reaction time in a PFR or batch reactor.
  5. For free radical polymerization, the chain growth time is usually much less than the mean residence time.
  6. When the chain growth time < mean residence time, a CSTR will have a narrower MWD than a PFR or batch reactor because all reaction in a CSTR takes place at the same monomer concentration.
From studying this module, you should now be able to:
  • Decide what type reactor should be used for a particular polymerization.
  • Explain how residence time distribution affects molecular weight distribution.
  • Calculate mass balances for polymerization in a CSTR.
 
Prepared by John L. Falconer, Department of Chemical and Biological Engineering, University of Colorado Boulder