Characterization of bioplastics developed from whole seaweed biomass (Kappaphycus sp.) added with commercial sodium alginate

Biodegradable plastics developed from renewable resources are currently being actively promoted as viable alternatives to reduce plastic pollution, particularly for single-use food packaging. Seaweeds, an abundant and relatively inexpensive biomass, demonstrate good film-forming properties ideal for bioplastic production. In this study, whole biomass (WS) of the red seaweed Kappaphycus sp. was used as the main ingredient to develop thin bioplastic sheets. To enhance physical properties, commercial sodium alginate (CA) was added at the ratios of (WS:CA) 100:0, 75:25, 50:50, 25:75, and 0:100 with 1.0% (v/v) glycerol as a plasticizer. Using standard methods, the bioplastics were then analysed for functional group, visual appearance, mechanical property, thermal property, water barrier property, and biodegradability. As a result, bioplastics with 0.050–0.054 mm thickness (within the range of commercial food packaging) were developed. With higher CA content, the visual appearance of bioplastics decreased in terms of colour difference and opacity. At around 23% moisture content, tensile strength (< 10 MPa) and thermal stability decreased with higher CA content while elasticity and water barrier property increased. All the bioplastics became fully degraded within 15 days. The results suggest that adding sodium alginate may have reduced the hydrophobicity of the WS bioplastics. This study demonstrates the potential of using WS biomass blended with commercial sodium alginate as base material to produce highly degradable bioplastics with the added benefits of protective and nutritious qualities naturally occurring in seaweed biomass.