Skip to main content
White Papers

Addition Versus Condensation Polymerization

Polymers are macromolecules that are based on a structure built-up, chiefly or completely, from a larger number of similar structural units bonded together. Often called chains, the polymer consists of repeating units, similar to links. Polymers are formed through a process known as polymerization, in which monomer molecules are bonded together through a chemical reaction that results in a three-dimensional network of long individual polymer chains consisting of smaller repeated units.

There are two basic types of polymerization reactions: addition and condensation. Addition polymerization is the formation of polymers from monomers containing a carbon-carbon double bond through an exothermic addition reaction. Significantly, this reaction proceeds without the loss of any atoms or molecules from the reacting monomers. Common materials produced through addition polymerization include polyethylene, polypropylene, poly(vinyl chloride), and polystyrene as represented here:

polymerization of styreneIn contrast, condensation polymers are formed by a stepwise reaction of molecules with different functional groups. The reaction is endothermic and produces water or other small molecules such as methanol, as a byproduct. Common polymers produced through condensation reactions include thermoplastic polyesters, polyacetal, polycarbonate, and polyamides as represented here:

Addition polymers form high molecular weight chains rapidly, and tend to be higher in molecular weight than condensation polymers. Comparing polymers produced via the two different mechanisms, addition polymers are generally, chemically inert due to the relatively strong carbon-carbon bonds that are formed. Condensation polymers tend to be susceptible to hydrolytic molecular degradation through exposure to water at elevated temperatures, through a mechanism that resembles the reversion of the initial liberalization reaction.

Polymers produced through these two different types of polymerization mechanisms exhibit inherently different characteristics, including mechanical, thermal, and chemical resistance properties. As such, it is important to understand the type of polymer being considered in an application.

Jeffrey A. Jansen

Jeffrey A. Jansen is the Engineering Manager and a Partner at The Madison Group. He was elected as a Fellow of the Society by the Society of Plastics Engineers. Jeff is a proven plastic professional with more than 30 years of experience solving problems and addressing opportunities related to polymeric materials. He specializes in failure analysis, material identification and selection, as well as compatibility, aging, and lifetime prediction studies for thermoplastic materials. Jeff has performed over 5,000 investigations, both for industrial clients and as a part of litigation. He regularly presents seminars and webinars, covering a wide range of topics related to plastics failure, material performance, testing, and polymer technology. Jeff is a graduate of Carroll College and the Milwaukee School of Engineering.