Enhancement of anti-corrosive performances of cardanol based amine functional benzoxazine resin by copolymerizing with epoxy resins

The bio-based amine functional benzoxazine (Bnz) resin was synthesized from cardanol, N,N'-Bis(2-aminoethyl)ethane-1,2-diamine and paraformaldehyde by the Mannich condensation reaction. The additional amine functionality in Bnz resin was introduced by using multi functional amine (N,N'-Bis(2-aminoethyl)ethane-1,2-diamine) to react with monofunctional cardanol. The synthesized amine functional Bnz resin was chemically analyzed for amine value by volumetric titration method. The Fourier Transform Infrared spectroscopy (FTIR) and 1H-Nuclear Magnetic Resonance (1H NMR) spectroscopy used to illustrate the structure of amine functional Bnz resin. The synthesized Bnz resin was copolymerized with conventional epoxy resins to prepare Poly(Benzoxazine-co-Epoxy) coatings for anti-corrosive application. The network formation of Bnz and epoxy resins was monitor by FTIR analysis. The Poly(Benzoxazine-co-Epoxy) coatings have shown good mechanical, chemical, and solvent resistance properties as compared to the crosslinked Polybenzoxazine coating. Further, gel content and water absorption of Poly(Benzoxazine-co-Epoxy) and Polybenzoxazine coatings were also studied. The cured coatings were evaluated for thermal behavior by thermogravimetric analysis (TGA). The corrosion resistance properties of coatings were investigated by salt spray and electrochemical analysis.