Polymer Reactor Design 2

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Polymer Reactor Design 2

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

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