Catalysts and Latent Curing Agents

Therefore, catalysts merely act as an initiator and promoter of epoxy resins curing reactions. The amounts of catalyst used with epoxy resins are usually determined empirically and are chosen to give the optimum balance of properties under the required processing conditions. Generally, only several parts per hundred of catalyst is used with an epoxy resin. Excess amounts of catalyst can result in poor physical properties and degraded resin. 

Catalysts can be used with epoxy resins in any of two primary ways  

As an accelerator in conjunction with another catalyst or with a curing agent such as polyamine, polyamide, or anhydride 

This section reviews the function of a catalyst as a sole crosslinker in epoxy resin systems. Their function as accelerators is covered under the sections related to the specific curing agent. 

Some catalysts, such as certain Lewis acids, are so reactive that they can provide extremely short gel times with epoxy resins at room temperature.15 For example, BC13, can polymerize epoxy resins, resulting in gel times of less than 60 s. However, these reactive systems result in a very rigid adhesive with low peel strength properties and poor impact strength. As a result, less reactive catalysts are commonly employed in adhesive formulations. 

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