Vazo radical initiators are substituted azonitrile compounds that thermally decompose to generate two free radicals per molecule. (Nitrogen gas is also generated.) The rate of decomposition is first-order and is unaffected by contaminants such as metal ions. The most important criterion for choosing the correct grade of Vazo™ free radical sources is the temperature at which the reaction is to be run. Vazo radical initiators are generally used within a range of 10 to 30°C (18 to 54°F) above the temperature corresponding to the grade number. This range is a rough guideline only. For instance, Vazo 64 has been used at 125°C (257°F), where the half-life is less than 1 minute.
Vazo free radical sources are used to initiate bulk, solution, and suspension polymerizations. These azo initiators can be used alone, or in combination with other free radical initiators. General benefits versus peroxide alternatives include: Head-to-Tail polymerization with less branching/crosslinking, higher control of molecular weight, lower polydispersity, unaffected by heavy metals, contamination, additives etc, and can polymerize oxidation susceptible compounds and functional groups. For more information about Vazo free radical sources, go to our guide in the Article section.