Bioplastic films from Sargassum oligocystum and Eucheuma spinosum seaweeds: Preparation, thermal degradation, and kinetics analysis

Abstract

In the framework of a circular economy, bioplastics derived from renewable natural resources are gaining attention as sustainable alternatives to conventional plastics. This study reports the synthesis of bioplastic films from brown seaweed (Sargassum oligocystum) and red seaweed (Eucheuma spinosum) via alginate extraction, followed by structural and thermal characterization. Fourier-transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, and differential scanning calorimetry results confirmed that Sargassum oligocystumbased bioplastic exhibited properties comparable to the commercial sodium alginate-derived bioplastic. Additionally, thermogravimetric analysis results revealed that Sargassum oligocystum decomposed in a single step near 220 ◦C, whereas Eucheuma spinosum degraded in two steps at ≈ 280 ◦C and 330 ◦C. The corresponding bioplastic films showed decomposition at ≈ 225 ◦C (Sargassum oligocystum) and 250 ◦C (Eucheuma spinosum). Kinetic studies indicated nucleation-controlled thermal degradation, with activation energies of 20.0 to 26.8 kJ/mol for Eucheuma spinosum and 43.8 to 49.5 kJ/mol for Sargassum oligocystum bioplastics. These findings demonstrate the potential of seaweed-derived bioplastics as renewable, thermally stable materials and provide insights into their degradation mechanisms for future material optimization and practical applications.