Sustainable Polyurethane Foams from Biomass Residues of Acacia dealbata

Polyurethane (PU), one of the most widely used polymers, is almost entirely produced from fossil-derived polyols and isocyanates, making its production highly dependent on non-renewable resources. At the same time, Acacia dealbata (mimosa) is one of the most invasive plant species in Portugal, causing severe ecological impacts by displacing native vegetation and reducing biodiversity. This study addresses both challenges by valorizing Acacia dealbata residues as a renewable feedstock for biopolyol production and PU foam synthesis. Branches of Acacia dealbata were subjected to acid-catalyzed liquefaction, achieving a liquefaction yield of 90%. The resulting biopolyol presented a hydroxyl index of 1388.61 mg KOH/g, demonstrating its suitability for PU production. PU foams were synthesized using different isocyanate concentrations to evaluate the effect of the isocyanate-to-polyol ratio on mechanical performance. Compression testing showed that the foams exhibited compressive strengths between 90 and 130 kPa. Increasing the isocyanate content improved compression resistance, highlighting the importance of optimizing formulation parameters. Although the mechanical performance was slightly lower than that of commercial PU foams, the developed materials displayed comparable properties, confirming their potential for practical applications. The results demonstrate the feasibility of converting Acacia dealbata biomass into functional PU foams while simultaneously contributing to invasive species management and reducing dependence on fossil-based raw materials. This approach supports climate change mitigation, resource conservation, and the transition towards more sustainable polymer production. Moreover, the valorization of Acacia dealbata is fully aligned with circular economy principles, transforming problematic biomass into high-value materials. Future work should focus on process scale-up, economic assessment, and industrial implementation to further advance the replacement of conventional fossil-based polyols with renewable alternatives in polyurethane manufacturing.