Classification of Polymers Based on Polymerization Reactions

There are two fundamental polymerization reactions: chain polymerization and step polymerization.
This classification is of particular importance to thermosetting systems which polymerize in situ when used in processes.

Chain polymerization is characterized by the presence of a few active sites which react and propagate through a sea of monomers. Polymerization may occur by any of the three following mechanisms:

• free radical
• cationic
• anionic

Vinyl monomers frequently undergo chain polymerization. Polymers formed via this process include:

• Polyethylene
• Polystyrene
• Polypropylene
• Polymethyl Methacrylate