Epoxidation of Black Seed Oil: <scp>RSM</scp> ‐Guided Optimization, Molecular Characterization, and Application in Amine‐Cured Epoxy Coatings

ABSTRACT We report an optimized epoxidation route for black seed oil (BSO) using in situ performic acid generated from H 2 O 2 and formic acid under moderate temperature, metal‐free and chlorinated‐solvent‐free conditions. After a range‐finding one‐factor‐at‐a‐time study (60°C–80°C; H 2 O 2 /C=C = 1.00–2.00; 60–120 min), a three‐factor Box–Behnken design (65°C–75°C; 1.00–1.50; 110–130 min) was employed to maximize epoxide formation while limiting side reactions. FTIR, 1H NMR, and 13C NMR corroborated the selective conversion of C=C to oxirane. The operating optimum—70°C, H 2 O 2 /C=C = 1.25, 120 min—afforded 98.22% conversion and an epoxide content of 5.96 mol mol −1 oil; confirmation runs yielded 96.63% (1.62% deviation), supporting model predictability. The quadratic model exhibited excellent statistics ( R 2 = 0.9998; Pred‐ R 2 = 0.9971) with global desirability = 1.000 under a single‐objective target (maximize conversion). Coating‐scale feasibility was demonstrated in epoxy–amine films containing EBSO, which show the expected plasticization trade‐off—improved compliance/flexibility and higher gloss at the expense of strength/modulus—alongside a decrease in the apparent low‐temperature onset ( T 5% and T 10% ) associated with early mass loss, a modest shift of the main DTG peak temperature (DTG‐ T max ), and reduced char yield, while maintaining adequate thermal stability for coating applications. These results position epoxidized BSO as a renewable, reactive building block for thermosetting polymers and UV‐curable coatings. Overall, the study provides a statistically validated, scalable processing window for epoxidation of BSO and, to the best of our knowledge, is among the first to directly couple an RSM‐optimized peracid epoxidation of black seed oil with a systematic evaluation of epoxy–amine coating performance on cementitious substrates, thereby illustrating how an underutilized regional oil can be upgraded into high‐performance epoxy‐based coatings.