Madhuca indica (Mahua) seed oil towards synthesis of alkyd-type polyurethane anticorrosive coatings

A series of biobased alkyd resins having hydroxyl functionalities was synthesized using Madhuca indica (mahua) seed oil as a renewable source on reaction with various diacids and anhydrides. Functional group transformation and alkyd formation were confirmed by ATR-FT-IR and proton NMR spectroscopies as well as by end group analysis. Polyols containing hydroxyl functionalities were utilized in combination with polymeric methylene diphenyl diisocyanate (PMDI) to produce polyurethane (PU) in the form of coatings, which were examined for their gloss, impact, flexibility, cross -cut adhesion, etc. Anticorrosion property of coatings was investigated by immersion method and by electrochemical method in an aqueous salt solution. Additionally, coatings were subjected to their thermal behavior study using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). While crystalline and amorphous behaviors of PUs were studied by X-ray diffraction (XRD). The mahua oil -based PUs revealed excellent coating properties, thermal stability, and anticorrosion performance. Thus, untapped mahua oil can act as a good source of replacement for petroleum in the preparation PU coatings.