Eco-Friendly Chitosan-Stabilized Polyurethane Coatings: Synthesis, Characterization, And Enhanced Anticorrosion Performance On Mild Steel

Abstract

This work reports the synthesis and characterization of novel chitosan-stabilized (CS) monomers derived from terephthaloyl chloride and 4-aminophenol, and their subsequent conversion into polyurethane coatings (CS1, CS2, and CS3). The coatings were further modified with acrylic polyol and groundnut powder to improve anticorrosion performance on mild steel. Structural and functional properties were systematically examined using Fourier Transform Infrared (FTIR) spectroscopy, Nuclear Magnetic Resonance (NMR), Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA), Differential Thermal Analysis (DTA), Ultraviolet-Visible (UV–Vis) spectroscopy, contact angle measurements, Electrochemical Impedance Spectroscopy (EIS), and Cyclic Voltammetry (CV). FTIR and NMR confirmed the successful formation of amide and urethane linkages, while modifications introduced ester and aliphatic functionalities. Thermal studies revealed glass transition temperatures (Tg) between 105–120 °C, degradation onset above 310 °C, and char yields up to 22%, indicating excellent thermal stability. Optical analysis showed high molar absorptivity (~25,000 M⁻¹ cm⁻¹) with transparency above 85%. Contact angle measurements demonstrated enhanced hydrophobicity, increasing from 78° to 105°. Electrochemical studies established superior anticorrosion performance, with impedance moduli reaching 3 × 10⁶ Ω·cm² and redox currents as low as ~10⁻⁹ A, outperforming conventional polyurethane coatings. Comparative evaluation with reported systems highlighted CS2 for its optimized thermal and optical properties, while CS3 benefited from the incorporation of a sustainable bio-filler. These results demonstrate that CS-based polyurethane coatings are promising eco-friendly alternatives for industrial anticorrosion applications. Future work will focus on evaluating long-term durability and adhesion performance.