Polymer Reactor Design 2
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Polymer Reactor Design 2

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Polymer Reactor Design 2 Polymer Reactor Design 2 Presentation Transcript

  • Polymer Reactor Design By: M.Z.Iqbal Lecture 2
  • Contents
    • General introduction to Ionic polymerization
    • Cationic polymerization kinetics
    • Anionic Polymerization kinetics
    • Some controlling parameters and their effects
    • Chain transfer processes in ionic polymerizations
  • Introduction
    • Both anions and cations can initiate the polymerization
    • Anions are relatively easy to discus because the cationic initiators need some co-catalyst in the system.
    • Anionic pzn starts with the formation of carbanion which is further capable of propagation.
    • In cationic pzn, the initiation process consists of the interaction of cations with monomers to form carbonium ions.
    • Sometimes, conventional acid (proton transfer specie) acts to initiate the pzn.
    • The reaction with chloro acids is a bit different than floro acids due to certain reasons.
    • The same concept lies that rate of propagation step is independent of chain length.
    • Termination is a bit different from FRP reactions.
  • Kinetics of Cationic Polymerization
    • These kinetics are of special consideration because steady state hypothesis doesn't seem to apply always.
    • A generalized behavior of cationic pzn is discussed here:
  • General behavior Curve You need to solve the kinetic Example given in your text
  • Kinetics of Anionic Polymerization
    • This approach resembles with cationic pzn in treatment and in steady state treatment with FRPs.
    • From practical investigation, rate of pzn of styrene is proportional to the square of monomer conc., half power of KNH2 conc.
    • A mechanism was proposed meeting the above data.
    • Steady state conditions approach very rapidly as in case of FRPs because there is nothing like co-catalyst that delays the process.
  •  
  • Treatment
  • Influence of Dielectric Constant
    • In the ionic pzn, the change in di-electric constant changes the speed of reaction depending upon the mechanism of reaction.
    • As D.C. increases, rate if initiation would increase.
    • Increase in D.E. can either increase or decrease the termination process.
    • As a rule of thumb, increase in D.C. should decrease in D.P. when rate of termination also increases with D.C.
  • Chain Transfer Processes in ionic Polymerization
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