Carrageenan (Kappaphycus alvarezii) solid waste-derived cellulose as a potential filler in Poly(vinyl alcohol)–sorbitol bioplastic films: mechanical and physicochemical properties

Abstract

Cellulose from carrageenan industry waste was utilized as a potential cellulose filler in polyvinyl alcohol (PVA)–based bioplastics plasticized with sorbitol. This study aimed to valorize carrageenan industry solid waste as an alternative cellulose source and to investigate the effect of selected cellulose concentrations on the mechanical and physicochemical properties of PVA–sorbitol bioplastic films. Cellulose was extracted from carrageenan solid waste through alkaline delignification using NaOH followed by bleaching with H2O2. The bioplastic films were prepared using the solution casting method by incorporating cellulose at 0, 1.5, and 3 wt.% into the PVA–sorbitol matrix. The extracted cellulose and resulting films were characterized using fiber composition analysis, FTIR, SEM, mechanical testing, thickness measurement, and water absorption analysis. The carrageenan solid waste contained 7.67% cellulose with a 29.6% yield. FTIR spectra of the bioplastics suggested possible hydrogen-bonding interactions between PVA, sorbitol, and cellulose, while SEM analysis showed a denser and more compact morphology in the 3% cellulose formulation. Although cellulose addition showed no significant statistical effect, the 3% formulation exhibited the highest tensile strength (4.80 ± 0.52 MPa) and elongation (220.62 ± 98.52%), whereas 1.5% cellulose achieved the greatest elastic modulus (2.68 ± 0.53 MPa) and lowest water absorption (78.6 ± 1.49%). These findings demonstrate that carrageenan solid waste can serve as a potential filler PVA–sorbitol bioplastics, improving matrix compactness/interfacial compatibility and supporting the development of sustainable, biodegradable polymer materials.

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