Polymerization

Definition - What does Polymerization mean?

Polymerization is the process of formation of polymers from their respective monomers.

It is a process by which an organic compound reacts with itself to form a high-molecular-weight compound composed of repeating units of the original compound. When two or more monomers are involved, the process is called copolymerization or heteropolymerization.

The formation of stable covalent chemical bonds between the monomers sets polymerization apart from other processes, such as crystallization.

Polymerization is important because it is the process by which plastics are made. It affects numerous aspects of everyday life, as anything to do with plastic, fabrics or elastomers involves polymerization.

Corrosionpedia explains Polymerization

Polymerization is a process in which relatively small molecules called monomers combine chemically to produce a very large chainlike or network of molecules called a polymer. Usually at least 100 monomer molecules must be combined to make a product that has certain unique physical properties, such as:

  • Elasticity
  • High tensile strength
  • Ability to form fibers

These properties differentiate polymers from substances composed of smaller and simpler molecules.

Polymerization reactions proceed via either cationic or free-radical mechanisms. Cationic polymerization is less efficient than free-radical polymerization due to the caustic nature of cation-producing reagents.

There are two general types of polymerization reactions, both with many variations:

  • Addition polymerization, or chain growth polymerization - This is occurs when monomers combine without the elimination of byproduct molecules. Alkene, alkadienes and their derivatives are used as monomers. Addition polymerization reaction is very rapid, and takes place in three steps:

      1. Chain initiation
      2. Chain propagation
      3. Chain termination

  • Condensation polymerization, or step growth polymerization - This is occurs when releasing small molecules as byproducts, such as water or methanol in reaction. Examples include:
    • Plyamides
    • Polyacetals
    • Polyesters

Free radical polymerization is a process in which a polymer is formed from the successive addition of free radical building blocks, like polyethylene and polypropylene.

Copolymerization refers to methods used to chemically synthesize a copolymer. This process is used with nitrile rubber and ethylene-vinyl acetate.

Polymerization that is not sufficiently moderated and proceeds at a fast rate can be very hazardous. This phenomenon is known as hazardous polymerization and can cause fires and explosions.

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