Copolymer of eugenol-based and pyrogallol-based benzoxazines: Low curing temperature and enhanced corrosion resistance

In this work, eugenol/stearylamine-based benzoxazine (E-s) and pyrogallol/furfurylamine-based benzoxazine (PY-f) were synthesized from renewable raw materials and mixed to prepare a series of copolymers. The curing behavior of E-s/PY-f mixtures were characterized by differential scanning calorimetry (DSC). The result shows that the curing temperature decreased obviously with the increase of PY-f content. When the mass ratio of E-s to PY-f was 8:2, the exothermic peak temperature ( T p ) of the sample (EP20) dropped to 194 ℃, which was 70 ℃ lower than that of E-s. Then, the representative copolymerization mechanism of E-s and PY-f was proposed. Furthermore, EP20 was adopted to prepare the copolymer coating (PEP) on mild steel (MS) for anti-corrosion application. The results of electrochemical impedance spectroscopy (EIS) indicated that PEP-coated MS well kept its corrosion resistance after being immersed in 3.5 wt% NaCl aqueous solution for 30 days. Hence, the copolymer of bio-based benzoxazines is promising for preparing superior anti-corrosion material with low curing temperature.