Synthesis of waste soybean oil-based waterborne polyurethane for exploration of its green and various application

Waste soybean oil resulting from repeated cooking and heating is a significant component of food industry waste. Transforming this waste soybean oil into eco-friendly and various products offers an efficient solution to enhance resource utilization. This study employed thermal cycling treatment to simulate the cooking process of soybean oil and analyzed its impact on synthesizing epoxidized soybean oil, soybean oil polyols, and soybean oil-based waterborne polyurethanes. Waste soybean oil was demonstrated to be a cost-effective feedstock for producing vegetable oil-based waterborne polyurethanes. For more diversified applications, the synthesized waterborne polyurethanes were utilized in the preparation of carbon quantum dots, resulting in a diverse range of colors through the incorporation of gardenia pigments. Moreover, through complexing with gelatin, robust composite films and multicolored fluorescent anti-counterfeiting inks were produced. The waterborne polyurethane is found to form a composite cross-linking network with gelatin, resulting in an increase in tensile strength of 130.72% and elongation at break of 258.98% for the composite film compared to the pure gelatin film. In comparison to physical blending, chemical grafting of gardenia pigment enhances the printability and firmness of the ink. The printed pattern produced by the ink emits a vivid blue fluorescence when excited at a wavelength of 365 nm, making it valuable for anti-counterfeiting ink applications.