Sustainable gellan gum/microcrystalline cellulose foams: Preparation, characterization, and acoustic performance

This study addresses the demand for sustainable, lightweight, and efficient acoustic materials by developing and characterizing three types of Polyvinyl Alcohol (PVA)-based foams reinforced with Microcrystalline Cellulose (MCC) as a homo-polysaccharide biopolymer, Gellan Gum (GG) as a hetero-polysaccharide biopolymer, and an MCC/GG composite (1:1 mass ratio) at the thickness of 7 mm. All prepared foams achieved low densities (approximately 0.1 g/cm³) and high porosities (approximately 92%), with BET-BJH analysis identifying mesoporous structures characterized by type IV isotherms and H3 hysteresis loops. Notably, the PVA/GG foam demonstrated the highest mean pore diameter (9.38 nm) and total pore volume (0.0048 cm³/g), which directly influenced its functional superiority. Thermal analysis (TGA-DGA) revealed a synergistic effect in the composite foam, where GG enhanced early-stage stability (up to 262.08 °C) and MCC improved high-temperature resistance (up to 441.09 °C). Mechanical evaluations showed that the GG foam provided the highest structural integrity, yielding a compressive Young's Modulus of 0.45 MPa. In acoustic performance, the GG foam outperformed its counterparts with an average Sound Absorption Coefficient (SAC = 0.32), exhibiting peak efficiency in the critical 2-4 kHz range. Furthermore, increasing the GG foam thickness to 11 mm significantly enhanced performance, raising the Noise Reduction Coefficient (NRC) to 0.46 and the Sound Absorption Average (SAA) to 0.43. These findings demonstrate that GG is a more effective modifier than MCC for enhancing the mechanical and acoustic properties of PVA foams, providing a clear quantitative framework for the design of bio-based composites in targeted noise-control applications.