This study presents a solvent- and catalyst-free approach to synthesize non-isocyanate polyurethane (NIPU) films using soybean oil (SBO) as a renewable and sustainable starting material. The process involves converting SBO into epoxide SBO (ESBO), followed by carbonation with CO₂ to form carbonated SBO (CSBO). CSBO then reacts with three different aliphatic amines—1,2-ethylenediamine (EDA), 1,4-butylene diamine (BDA), and 1,6-hexamethylenediamine (HDA)—to produce NIPU films. The films were cast and cured at 85 °C for various durations, and their properties were evaluated. The effects of aliphatic diamines and curing times on the films' properties were analyzed using techniques such as Fourier transform infrared spectroscopy (FT-IR), 1H nuclear magnetic resonance (NMR), gel permeation chromatography (GPC), thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), and mechanical tests. The results showed that the NIPU films exhibited satisfactory thermal and mechanical properties, with the degree of swelling, gel content, and contact angle being influenced by the type of amine and curing time. The study highlights the potential of this green and scalable approach for the synthesis of NIPU films with desirable characteristics.This study presents a solvent- and catalyst-free approach to synthesize non-isocyanate polyurethane (NIPU) films using soybean oil (SBO) as a renewable and sustainable starting material. The process involves converting SBO into epoxide SBO (ESBO), followed by carbonation with CO₂ to form carbonated SBO (CSBO). CSBO then reacts with three different aliphatic amines—1,2-ethylenediamine (EDA), 1,4-butylene diamine (BDA), and 1,6-hexamethylenediamine (HDA)—to produce NIPU films. The films were cast and cured at 85 °C for various durations, and their properties were evaluated. The effects of aliphatic diamines and curing times on the films' properties were analyzed using techniques such as Fourier transform infrared spectroscopy (FT-IR), 1H nuclear magnetic resonance (NMR), gel permeation chromatography (GPC), thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), and mechanical tests. The results showed that the NIPU films exhibited satisfactory thermal and mechanical properties, with the degree of swelling, gel content, and contact angle being influenced by the type of amine and curing time. The study highlights the potential of this green and scalable approach for the synthesis of NIPU films with desirable characteristics.