Design and optimization of fully (100%) cellulose-based polyurethane foams: Strategies, challenges, and solutions for future applications

초록

The world is increasingly adopting sustainable materials to reduce CO2 emissions and combat global warming. Polyurethane (PU), a versatile polymer used across industries, is traditionally produced from petroleum-derived polyols and diisocyanates. Recently, cellulose, the most abundant natural biopolymer, has been investigated for PU synthesis but mainly served as a filler or chain extender alongside synthetic polyols rather than a sole polyol due to its strong intermolecular hydrogen bonding, which limits free hydroxyl groups, and its hygroscopic nature, which favours polyurea formation. This work reports, for the first time, the successful synthesis of pure cellulose-based PU films and foams using cellulose as a 100% bio-based polyol without any synthetic or petroleum-derived polyols. Four cellulose types, cellulose nanofibers (CNFs), cellulose nanocrystals (CNCs), hardwood (HW) pulp, and lignocellulose (LC), were used as polyols to synthesise cellulose-based PUs. FTIR and XPS confirm PU formation, while TGA reveals HW-PU has the highest thermal stability, highlighting its potential for high-performance applications. Morphological variations before and after PU synthesis further provide insights into physicochemical transformations. Among all cellulose materials, the HW pulp exhibits the highest reactivity toward diisocyanates, making it a promising polyol for PU synthesis. This HW-PU was subsequently dissolved in an ionic liquid to form soft films and foams, an area that has remained largely unexplored to date. This strategy opens a new avenue for utilising HW-pulp in next-generation PU technology.

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