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Elastomer Processing
Part 2

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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