Curing mechanisms with mercaptan

The mechanism of curing of epoxy resin with mercaptan has been proposed by Kamon44 and has been based on the work by Danehy46 ... 

The polyaddition reaction is the most commonly used type of reaction for the cure of epoxy resins. The curing agents used in this type of reaction have an active hydrogen compound, and they include amines, amides, and mercaptans. With this reaction mechanism, the most important curing agents for adhesives are primary and secondary amines containing at least three active hydrogen atoms and various di- or polyfunctional carboxylic acids and their anhydrides. 

The bismaleimides can be reacted with a variety of bifimctional compounds to form polymers by rearrangement reactions. These include amines, mercaptans, and aldoximes (Figure 4.22). If the reaction is carried out with a deficiency of the bifunctional compound, the polymer will have terminal double bonds to serve as a cure site for the formation of a cross-linked polymer via a double bond polymerization mechanism during molding. The cross-linked in this case occurs without the formation of any volatile by-products. 

Other curatives, which react through addition mechanisms are phenolic resins, particularly if the hydroxyl/epoxy reaction is catalysed using a tertiary amine (usually accomplished at elevated temperatures), thiols, polysulphides and mercaptans (can be formulated to give very rapid cures), polyetheramines (relatively slow cures, which can be accelerated with nonyl phenol), polyamides (less reactive than their amine counterparts) and amidoamines (characterized as having very long pot lives). 

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