Cellulose nanocrystal/phytic acid-enhanced non-isocyanate polyurethane foams

Carbon dioxide-derived non-isocyanate polyurethane (NIPU) foams have attracted wide attention because of their remarkable benefits for sustainable development and green production. While progress has been made in synthesizing NIPU to replace petroleum-based counterparts, challenges persist in achieving high-performance, multifunctional, and recyclable NIPU foams through an eco-friendly foaming process. In this study, we present a green fabrication protocol employing a solvent-free process with HFO-1233zd(E) as an eco-friendly blowing agent, foaming at mild foaming temperatures that reduce the impact on the environment. For the first time, we propose a method that combines renewable biomass components—cellulose nanocrystals (CNC) and phytic acid—with NIPU. This combination synergistically enhances mechanical strength (showing a threefold improvement compared to CNC-free foams), flame retardancy (exhibiting self-extinguishing behavior), thermal stability (with a 15 % residual mass), and unconventional fluorescence properties. A systematic investigation using small-amplitude oscillatory shear rheological analysis allowed for precise modulation of the critical balance between gelation kinetics and foaming dynamics. Through this optimized protocol, we overcome the limitation of NIPU foams, which traditionally served a single function, by simultaneously achieving thermal insulation, flame resistance, and fluorescence. The catalyst-free circularity of the process enables foam reprocessing through the presence of abundant hydroxyl groups and autocatalytic tertiary amines of PEI, eliminating the need for additional catalysts. The biomass-derived additive system, combined with dynamic covalent networks, establishes a sustainable paradigm for developing advanced multifunctional foams, thereby broadening their applications in fields such as architecture, home furnishing, shipping, and packaging.