Sustainable Xylose-Based Non-Isocyanate Polyurethane Foams with Remarkable Fire-Retardant Properties

Self-blowing non-isocyanate polyurethane foams have been synthesized by reacting xylose with dimethyl carbonate and hexamethylene diamine using citric acid as a natural crosslinker via the process of transurethanisation. The resulting foams exhibit exceptional flame retardancy in comparison to conventional PU foams. The structure of the foam cells was examined using scanning electron microscopy. Solid-state NMR and infrared spectroscopy were used to analyze the functional groups present in the products formed. The formation of the urethane bridge was confirmed by the emergence of peaks at 158.24 ppm and 1693 cm(- 1) respectively. The thermal properties were evaluated by using TGA and DSC, which further indicated a glass transition temperature of around 112.82 degrees C. The dependence of viscosity of polymeric solutions on the different shear rates was also studied using a parallel plate rheometer. Limiting Oxygen Index was employed to study the flammability of the prepared foams, and it was observed that they exhibit considerable fire resistance (26.9%),which is quite comparable to the fire resistance offered by the isocyanate-based polyurethane foams with added fire retardants. The diffraction pattern of the prepared NIPU was analyzed by PXRD.