Synthesis, structure, and mechanical properties of castor oil‐based polyamidoamines toughened epoxy coatings

A series of toughened epoxy systems was prepared via crosslinking of diglycidyl ether of bisphenol A with castor oil-based polyamidoamines as curing agents. To this aim two series of polyamidoamines were synthesized in two steps from the reaction of castor oil with triethylenetetramine and then reaction of these products with dissolved salicylic acid in dimethyl formamide (DMF). The structure of the compounds was confirmed by FTIR spectra, GC-Mass and 1H-NMR spectroscopy. The mechanical properties, adhesion and water resistance of polyamine and polyamidoamines cured epoxy systems were studied. It was found that significant improvement in toughness and adhesion of the epoxy films was achieved by using polyamidoamines as curing agents. The results showed a great enhancement in toughness and adhesion properties of the epoxy coats proportional to increasing castor oil weight ratio, and/ or using salicylic acid and DMF. Furthermore, polyamidoamines cured samples showed higher water resistance and less degradation in hot water immersion tests than polyamine cured samples. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013