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POLYAMIDE RESINS ARE POLYCONDENSATION products of dimerized fatty acids and polyamines. Reactive liquid polyamide resins are oligomers designed primarily for use in the manufacture of two-component epoxy/polyamide coatings and adhesives. The two-component coatings are generally labeled Part A and Part B, with the liquid polyamide resin usually (though not always) contained in Part B. The polyamide resin may function as the curing agent, core-actant, or hardener for epoxy resin. Polyamide resins should not be considered as catalysts although they may initiate the reaction; the polyamide resin reacts with the epoxy resin and becomes part of the polymer. The majority of polyamide resins used in coatings are viscous liquids that are usually supplied by the coatings manufacturer as a solution in organic solvents. The solution may be a clear amber liquid or may contain pigments in colored systems. Current trends in the coatings industry are toward higher solids, lower volatile organic compound (VOC)-containing products. These products require lower viscosity reactants, such as liquid epoxy resins cured with amidoamines rather than polyamides. Amidoamines are condensation products of monobasic fatty acids and polyamines and are therefore lower in viscosity. These products are less compatible with epoxy resins so commercial examples are adducts of amidoamines. Adduction improves compatibility, though generally increases viscosity, so high boiling, compatible solvents, such as benzyl alcohol, are commonly used to reduce viscosity. Benzyl alcohol becomes trapped in the cured film due to its structural similarity to epoxy resins based on bisphenol A and does not migrate through the film to the surface. Many commercial high-solids curing agents are amidoamine adducts containing benzyl alcohol.
Kight, Robert W.
Arizona Chemical Company, Savannah, GA