Bio-based polybenzoxazines as an efficient coatings to protect mild steel surfaces from corrosion
Sharanya Ranganathan, Hariharan Arumugam, Balaji Krishnasamy, Subramanian Sathy Srikandan, M. Kumaravel, M. Alagar
Abstract
New types of mono and bi-functional benzoxazine monomers were synthesized using cardanol (C) and 4-aminobenzonitrile (abn), p-phenylediamine ( ppda) along with paraformaldehyde. The synthesized benzoxazine monomers structure was elucidated by 1H, 13C-NMR and FTIR spectroscopic techniques. The polymerization temperature (T p ) of C-abn and C- ppda are noticed at 280 o C and 237 o C, respectively. It was also noticed that bi-functional benzoxazine (C- ppda) possesses lower curing temperature than mono-functional benzoxazine (C-abn). The ring opening polymerization of benzoxazine was confirmed by FTIR spectroscopy. Thermal analyses indicate that, benzoxazine [poly(C- ppda)] possesses higher thermal stability than poly(C-abn). The surface roughness of the benzoxazine coated MS specimen was analysed by atomic force microscope. The values of water contact angles obtained for poly(C-abn) and poly(C- ppda) are 145 o and 148 o, respectively. It was noticed that the mild steel specimen coated with bio-based benzoxazine C-abn exhibit excellent resistance to corrosion.