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Elastomer Processing
Part 2

polymerization reactions

Types of Polymerization Reactions

  • 1. Condensation Polymerization-
    yields polymers with repeating units having fewer atoms than the monomers from which they are formed. This reaction generally involves the elimination of small molecules such as H2O or HCl.
     
  • 2. Addition Polymerization
     
  • 3. Chain Polymerization/Free Radical Polymerization-
    • A. Initiation: formation of free radicals by scission of a single bond (homolysis), or by the transfer of a single electron to or from an ion or molecule (redox).
    • B. Propagation: growth of macromolecular structure.
    • C. Chain Transfer and Termination: completing the polymerization step.

Types of Chain Polymerization Methods

  • Bulk Polymerization-
    involves only the monomer and a monomer-soluble initiator.  
  • Solution Polymerization-
    a solvent lowers the viscosity, assisting heat transfer and reducing the likelihood of auto-acceleration.  
  • Suspension Polymerization-
    reaction mixture is suspended as droplets in an inert medium. Polymer particles are produced in the form of beads in the range of 0.1 to 2 mm in diameter.  
  • Emulsion Polymerization-
    the initiator is not soluble in the monomer but soluble only in the aqueous dispersion medium. Polymer is produced in the form of a latex with particles in the range of 0.05 to 1 micron.

Next Topic Elastomer Processing Part 3

 

 

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