Utilization of Rice Straw Pulp as a Reinforcing Filler in Hydroxyethyl Cellulose/Gellan Gum/Alginate Bio-Composite Gel Foams

To address the environmental impact of synthetic foams, this study developed sustainable composite gel foams (CGF) based on hydroxyethyl cellulose (HEC), gellan gum (GG), and sodium alginate (Al) reinforced with rice straw (RS) pulp. The CGFs were fabricated using solution casting followed by freeze-drying, with RS pulp content varied from 0% to 4% (w/v). SEM analysis revealed that RS pulps acted as physical fiber reinforcement, promoting a more interconnected and robust porous network. FTIR spectra confirmed the successful integration of RS pulp through characteristic lignin peaks at 1540 cm−1. Adding RS pulp clearly improves the foam’s mechanical strength, notably its compressive strength and Young’s modulus, over the control sample. All of these best mechanical, water retention, and structural stability properties resulted from the 2% (w/v) RS pulp addition, which was attributed to the formation of a dense, interconnected fiber-reinforcing network and tortuous microporous channels that provided high capillary resistance and physical constraints against structural deformation. Especially, the CGF exhibited exceptional water absorption capabilities, exceeding 1900% in the initial stages. The thermal stability of CGF was also characterized via TGA, showing consistent performance across different RS pulp loads. These findings demonstrate that the RS pulp-reinforced HEC/GG/Al CGFs are promising candidates for high-performance, eco-friendly absorbent fibrous gel foam pads in food packaging applications.