Synthesis and Structural Characterization of Neem Oil-Derived Bio-Polyol as a Sustainable Precursor for Bio-Based Polyurethane Production

The growing demand for sustainable and environmentally friendly materials has intensified the search for renewable alternatives to petroleum-derived polyols used in polyurethane production. In this study, neem oil (Azadirachta indica), a non-edible and renewable vegetable oil, was chemically modified through a calcium oxide (CaO)-catalyzed glycerolysis process to produce a bio-based polyol suitable for polyurethane applications. The reaction was conducted in a batch reactor at 225 °C for 180 min under controlled operating conditions. The synthesized bio-polyol was characterized using Fourier Transform Infrared Spectroscopy (FTIR) and Gas Chromatography–Mass Spectrometry (GC–MS) to evaluate its structural and chemical properties. FTIR analysis revealed the presence of hydroxyl functionalities, evidenced by a broad absorption band around 3300 cm⁻¹, confirming successful functionalization of the neem oil. GC–MS analysis showed that alcohols and esters constituted 71.68% of the reaction products, indicating a substantial degree of conversion during glycerolysis. Physicochemical characterization demonstrated significant reductions in acid value and free fatty acid content, accompanied by a marked increase in viscosity, reflecting effective molecular restructuring of the oil. These findings confirm the successful synthesis of a hydroxyl-functionalized neem oil-derived bio-polyol and highlight its potential as a sustainable precursor for the development of bio-based polyurethane materials. The study contributes to ongoing efforts toward the utilization of renewable feedstocks in environmentally responsible polymer production.