Lab-scale biocomposite manufacturing: Exploring rice bran-based bioplastics reinforced with natural fillers through extrusion and injection molding

Bioplastics from agro-food industry by-products offer a sustainable alternative to the environmental concerns linked to petroleum-derived plastics. Rice bran (RB), an abundant and low-cost by-product rich in protein and starch, is a promising feedstock but poses challenges due to its complex composition. This study investigates the integration of natural fillers (cellulose, flax, and hazelnut shell) into a RB-based matrix. At low filler content (2 wt.%), all fillers increased stiffness from 138 MPa to 190, 184 and 196 MPa for cellulose, flax and hazelnut shell, respectively. Higher contents (5–10 wt.%) showed varied effects: flax and cellulose improved Young's modulus only up to 5 wt.% due to agglomeration, while hazelnut shell had beneficial effects even at 10 wt.% even for tensile strength (improving from 2.5 to 3.4 MPa). Additionally, all fillers enhanced viscoelastic moduli and thermal stability, with hazelnut shells showing the most significant improvements, making them a promising additive for bioplastics.