Epoxy adhesives mercaptan curatives

Epoxide adhesives comprise epoxy resin, many of which are prepared from phenols and epichlorohydrin, for example, the diglycidyl ether of bis-phenol A or bis-phenol F usually, these resins are a mixtnre of molecular weights blended to fit the applications. The most-common cnratives for epoxy resins are polyanfines (used in stoichiometric amounts), usually a chain-extended primary aliphatic amine, for example, diethylene triamine or triethylene tetraamine or chain-extended equivalents, which react rapidly with the epoxy resin at room temperature. Aromatic amines react slowly at room temperature but rapidly at higher temperatures. Most epoxide adhesives also contain catalysts, typically, tertiary amines. Dicyanimide is the most-common curative for one-component high-temperature-cured epoxide adhesives. Mercaptans or anhydrides are used as curatives for epoxide adhesives for specialist applications, for example, for high-speed room-temperature cures or for electronic applications. A smaller number of epoxide adhesive are cured by cationic polymerization catalysed by Lewis acids photogenerated at the point of application. Lewis acid photoinitiators include diaryliodonium and triarly sulphonium salts. See Radiation-cured adhesives. 

Chem. Descrip. Mercaptan polymer precatalyzed, accelerated Uses Epoxy hardener, accelerator in concrete adhesives, grouts, mortars, and coatings co-curative improves bond to glass and metal Features Fast cure eliminates induction times of polyamides and amido-amines... 

Lewis and Bronsted acids, activate the epoxy ring toward ring opening by various nucleophilic species, most often hydroxyl or other epoxy groups (Eqs. 2-4). Both types of curatives can take the form of catalytic species, such as tertiary amines and Lewis acids, or coreactants, such as primary amines, mercaptans, and dicarboxylic acids. When the curatives are catalytic species, the properties of the cured adhesive are due primarily to the epoxy resin and the stability/activity of the catalyst in the resin under cure conditions. Coreactant curatives offer much greater latitude in choosing the final cured adhesive properties because the physical characteristics of the... 

---