Investigation of cardanol-based reactive polyamide as a crosslinker in epoxy zinc-rich primer

Cardanol-based reactive polyamides with different amine functionalities 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 in the second 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 FTIR and NMR spectroscopy. These polyamides were then used as crosslinker in conventional epoxy zinc-rich primer. The effect of molecular weights of these polyamides on mechanical, chemical, and solvent resistance properties of conventional epoxy zinc-rich primer was studied and compared with that of commercial polyamide. The anticorrosive properties of the primers were evaluated by humidity resistance test, salt spray test and electrochemical impedance spectroscopy. The study revealed that the epoxy zinc-rich primers cured with cardanol-based polyamide resulted in improved mechanical, chemical, and anticorrosive properties as evaluated by various methods.