Hydrophobic and Superhydrophobic Bio-Based Nano-Magnetic Epoxy Composites as Organic Coating of Steel

New epoxy resin hardeners were prepared from the reaction of p-nonylphenol and cardanol glycidylether with pentaethylenehexamine (PEHA) to produce hydrophobic polyamines. They were used as capping to produce superhydrophobic magnetite nanoparticles (Fe3O4 NPs). The chemical structures, thermal stability, morphologies, and particle sizes diameters were evaluated to confirm the hydrophobicity of dicardanoxy (DCHI) and dinonylphenoxy (HPHI) polyamines. The curing exothermic reaction of bisphenol A diglycidyl ether (DGEB) epoxy resin with DCHI, HPHI, or their Fe3O4 NPs was investigated by dynamic mechanical analyzer and differential scanning calorimetry. The cured epoxy networks crosslinking densities, storage modulus, and glass transition temperatures were determined and correlated to epoxy networks chemical compositions. DGEB/DCHI and DGEB/HPHI with their stoichiometric ratio embedded with their Fe3O4 NPs were applied on the rough steel surface to produce hydrophobic and superhydrophobic epoxy coatings. The wetting characteristics of the cured epoxy nanocomposites were evaluated from seawater contact angle (WCA) measurements to prove the formation of superhydrophobic coatings in the presence of DCHI-Fe3O4 NPs having WCA > 150°. The excellent adhesion, mechanical, and anti-corrosion performances using DGEB/DCHI and DGEB/HPHI epoxy nanocomposites were obtained on the steel surfaces in the presence of seawater corrosive environment.