Synthesis and characterization of cardanol based reactive polyamide for epoxy coating application

Cardanol based reactive polyamides having different molecular weights were successfully developed by conventional polycondensation mechanism. The synthesis involved 2-step processes of functionalization of cardanol by maleic anhydride followed by its condensation with diethylenetriamine (DETA) in the 2nd step. The polyamides with different molecular weights were prepared by varying the mole ratios of acid and amine components in the formulation. The developed polyamides were characterized for structural confirmation by FT-IR and NMR spectroscopy. These polyamides were then used as curing agents for thermally curable epoxy coatings. The effect of molecular weights of these polyamides on mechanical, chemical, thermal and solvent resistance properties of conventional epoxy resin was studied and compared with that of commercial polyamide. The anticorrosive properties of the coatings were evaluated by salt spray test and electrochemical impedance spectroscopy. The study revealed that the performance properties of cured material improved with increase in amine value of polyamides due to increased cross-link density. The anticorrosive performance also improved as indicated by higher impedance and electrochemical potential values.