Synthesis of Hydroxyl Terminated Fatty Ester Amide (DFEAm) from Dehydrated Castor Oil (DCO) and its Utilization in Various Polyurethane Coating Applications

Abstract

Vegetable oils have gained popularity now-a-days as renewable resources due to their accessibility, affordability, non-toxicity and biodegradability. Globally, scientists have been making efforts to lessen dependency on feed stocks derived from petroleum-based resources. Dehydrated castor oil (DCO) being bio-based, non-edible, quick-drying compared to castor oil, imparting flexibility and excellent color retention was used as the main source of raw material in this work. Present study aims at single-step synthesis of dehydrated castor oil fatty amide (DFAm) by reacting dehydrated castor oil (DCO) with diethanolamine (DEA) avoiding the methyl ester synthesis step. The product obtained was then purified and characterized chemically and analytically. Further, DFAm was modified successfully to its hydroxyl-terminated fatty ester amide (DFEAm) derivative using sebacic acid (SA) and tris-2-hydroxyethyl isocyanurate (THEIC). THEIC, being heterocyclic in nature and imparting excellent thermal and chemical resistance, makes it suitable and novel to be used in coating applications. DFEAm was then successfully cured with various isocyanate adducts on mild steel substrates. Commercially available hydroxyl-terminated short oil alkyd was selected for comparative study under simultaneous conditions. These polyurethane coatings were evaluated as per ASTM standards for their optical, mechanical, chemical, thermal and anti-corrosive properties. DFEAm PU coatings exhibited comparable mechanical and inferior chemical properties but superior thermal and anti-corrosion properties than that of the commercial PU coatings.

Graphical Abstract