Biorenewable vegetable oil based nonisocyanate polyurethanes and nanocomposites; formulation, characterisation, biodegradation, anticorrosion and antifouling coatings

Abstract

To develop efficient coatings from a biobased vegetable oil (castor oil, CO) towards the elimination of fossil resources as well as the prevention of the impact of microorganisms on the surface of maritime vessels, coatings of biorenewable and biodegradable nonisocyanate polyurethane (NIPU) and nonisocyanate polyurethane nanocomposite (NIPU-F) were formed. The biorenewable precursor, CO, was transformed into the cyclic carbonate (CO–CC) substrate to form NIPU upon reaction with a long chain aliphatic diamine (1,12-diaminododecane) via a facile one pot reaction followed by film casting to recover the NIPU film. Furthermore, the protocol to form NIPU-F was executed by incorporation of synthesised amine-functionalised silica coated iron oxide nanoparticles (Fe₃O₄@SiO₂–NH₂) into the NIPU matrix via covalent bond formation. Subsequently, the physicochemical (¹H and ¹³C NMR, FTIR, XRD and VSM), thermal (TGA and DSC) and morphological (SEM, optical microscopy and EDAX) characterization of NIPU and NIPU-F films was performed along with water contact angle and biodegradation studies. The results highlighted that the synthesized NIPU shows the highest T_g value of 55 °C with the average static water contact angle of 44°. The hydrophilic properties of above polymeric samples are identified as appropriate for applications in coatings towards antifouling, antibacterial and anticorrosion protection on submerged solid surfaces. As such the results from studies on NIPU and NIPU-F coatings indicated their remarkable resistance against E. coli bacteria with reduction rates of 99.7 and 88.7% respectively. Indeed, the settlements of algae like Spirulina platensis (S. platensis) on NIPU and NIPU-F diminished significantly by 71.2% and 52.9%, respectively, as compared to that of the control sample. Furthermore, the electrochemical impedance spectroscopy (EIS) studies suggested that when immersed in electrolyte solution for over a period of 24 h, the anticorrosion performance of both NIPU and NIPU-F attained a comparable level, with impedance magnitudes |Z| of ∼ 1.6 × 10³ and ∼1.7 × 10³ Ohm, respectively. Herein, the demonstration of EIS studies in 3.5 wt% NaCl and inhibition studies against microorganisms in marine environments for NIPU and NIPU-F paves new routes for applying such coatings in a practical environment.