Synthesis and characterisation of new modified polyesteramide resins based on sunflower oil for anticorrosive protective coatings

Polyesteramide resins were successfully synthesized via aminolysis of sunflower oil with diethanolamine under mild catalytic conditions, yielding N,N-bis(2-hydroxyethyl) sunflower amide (HESA) with a hydroxyl value of 9.02 mg KOH/g. HESA was then polymerised with N,N-Bis(4-hydroxyphenyl)maleamic acid (BHPMA) and N,N-Bis(4-sulfonicphenyl)maleamic acid (BSPMA) to form modified polyesteramide resins for protective coating applications. The synthesized coatings, with a thickness of approximately 30 ± 5 µm, were evaluated for mechanical and chemical properties, including drying times ranging from 58 to 60 h under air-drying conditions, and enhanced corrosion resistance confirmed by 500-h salt spray tests. Analytical techniques such as FTIR, 1H NMR, and SEM confirmed the structure and morphology of the resins. The improved anticorrosive performance was attributed to the incorporation of sulfonic and aromatic groups, which enhance film density, chemical stability, and resistance to ionic penetration. The results support the application of these bio-based resins as eco-friendly and efficient protective coatings for industrial surfaces.