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    Enhancement of physico-chemical and anti-corrosive properties of tung oil based polyurethane coating via modification using anhydrides and inorganic acid

    Year: 2019

    Journal: Surf. Interfaces, Volume 15, JUN, page 180–190

    Authors: Shirke, Amit G.; Dholakiya, Bharatkumar Z.; Kuperkar, Ketan

    Keywords: Modified polyurethane (PU); Galvanized steel (GS); Mild steel (MS); Modifier cross-linker; Polarization; Corrosion; Electrochemical impedance spectroscopy (EIS); Salt spray; Surface characterization

    Tung oil (TO) based polyol was synthesized through hydroxylation and alcoholysis. Modification of synthesized polyol (purified alcoholysed hydroxylated tung oil (PAHTO)) was carried out using the definite proportion of phthalic anhydride (PA), maleic anhydride (MA) and boric acid (BA) acting as modifiers as well as cross-linkers. Modified polyurethane (PU) was prepared by reacting the modified polyol with toluene diisocyanate (TDI) in NCO/OH = 0.7 ratio. Spectroscopic studies of modified PU confirmed the modification process. Anti-corrosive properties of the modified PU on galvanized steel (GS) was found better than mild steel (MS) in aqueous (3.5 wt %) NaCl solution environment. The resultant surface hydrophobicity and roughness characterization along with its morphology were analyzed using the atomic force microscopy (AFM) and contact angle (CA). Chemical resistance properties, as well as the physical properties such as gloss, scratch hardness, adhesion and impact resistance, were evaluated using standard methods. It was observed that the cross-linking moiety in the backbone of the PU chain exhibits better physico-chemical properties compared to the unmodified PU. The thermal stability of modified PU coating was examined by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA) which showed that thermal properties like decomposition and glass transition of the materials increase with PA and BA molar ratio. The potentiodynamic and electrochemical impedance spectroscopy (EIS) study inferred better corrosion resistance property of PU with the incorporation of PA and BA which prepare itself for several industrial and commercial applications.
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